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Lower socioeconomic status (SES) is associated with shorter overall survival (OS) in patients with locoregional colon cancer. We aimed to estimate: (1) the proportion of SES-based OS disparities mediated by disparities in the quality and location of surgical treatment in patients with resected stage I–III colon cancer and (2) the relative importance of components of surgical quality. We examined patients ages 18–80 years with resected stage I–III colon adenocarcinoma using the 2010–2016 National Cancer Database. SES was defined at the zip code level. Inverse odds weighting mediation analysis was used to estimate the proportion mediated (PM) for nine treatment quality-related and facility-related factors and composite PMs in models including all nine mediators. Models compared high SES patients with each lower SES stratum. Among 171,009 patients, 5-year OS increased from 70.4% in low SES patients to 78.1% in high SES. When high SES patients were compared with low, lower-middle, and upper-middle SES patients, PM ranges among lower SES strata were: minimally invasive surgery 16.0–16.6%, lymph nodes examined 7.7–9.6%, positive margins 3.8–6.5%, length of stay 16.7–28.1%, readmissions insignificant to 3.7%, treatment at > 1 CoC facility 2.7–3.1%, facility type insignificant to 7.3%, facility volume 2.9–8.2%, and adjusted facility 90-day mortality rates 33.2–42.8%. Composite PMs were 76.9% (95% CI 61.3%, 92.4%) for low SES, 68.7% (95% CI 56.4%, 81.1%) for lower-middle SES, and 60.9% (95% CI 43.1%, 78.6%) for upper-middle SES. These data suggest that improving the quality of the surgical episode for disadvantaged patients undergoing resection for locoregional colon cancer could decrease SES-based survival disparities by over half.

Background The impact of molecular aberrations on survival after resection of colorectal liver metastases (CLM) in patients with early-age-onset (EOCRC) versus late-age-onset colorectal cancer (LOCRC) is unknown. Methods Patients who underwent liver resection for CLM with known RAS, BRAF and MSI status were retrospectively studied. The prognostic impact of RAS mutations by age was analysed with age as a categorical variable and a continuous variable. Results The study included 573 patients, 192 with EOCRC and 381 with LOCRC. The younger the age of onset of CRC, the greater the negative impact on overall survival of RAS mutations in the LOCRC, EOCRC, and ≤40 years (hazard ratio (HR), 1.64 (95% confidence interval (CI), 1.23–2.20), 2.03 (95% CI, 1.30–3.17), and 2.97 (95% CI, 1.44–6.14), respectively. Age-specific mortality risk and linear regression analysis also demonstrated that RAS mutations had a greater impact on survival in EOCRC than in LOCRC (slope: −4.07, 95% CI −8.10 to 0.04, P = 0.047, R2 = 0.08). Conclusion Among patients undergoing CLM resection, RAS mutations have a greater negative influence on survival in patients with EOCRC, more so in patients ≤40 years, than in patients with LOCRC and should be considered as a prognostic factor in multidisciplinary treatment planning.

The objectives of this expert review are: (1) to prepare clinicians to recognize the presentation and evidence-based risk factors for young adult-onset colorectal cancer (CRC), defined as CRC diagnosed in individuals 18 -50 years of age; (2) to improve management for patients with young onset CRC. This review will focus on the following topics relevant to young adult-onset CRC: epidemiology and risk factors; clinical presentation; diagnostic and therapeutic management including options for colorectal and extra-colonic surgical intervention, chemotherapy and immune-oncology therapies; genetic testing and its potential impact on preimplantation genetics; fertility preservation; and cancer surveillance recommendations for these individuals and their family members.The evidence reviewed in this manuscript is a summation of relevant scientific publications, expert opinion statements, and current practice guidelines. BEST PRACTICE ADVICE 1: With the rising incidence of people developing CRC before 50 years of age, diagnostic evaluation of the colon and rectum is encouraged for all patients, irrespective of age, who present with symptoms that may be consistent with CRC, including but not limited to: rectal bleeding, weight loss, change in bowel habit, abdominal pain, iron deficiency anemia. BEST PRACTICE ADVICE 2: Clinicians should obtain family history of colorectal and other cancers in first and second degree relatives of patients with young adult-onset CRC and discuss genetic evaluation with germline genetic testing either in targeted genes based on phenotypic presentation or in multiplex gene panels regardless of family history. BEST PRACTICE ADVICE 3: Clinicians should present the role of fertility preservation prior to cancer-directed therapy including surgery, pelvic radiation, or chemotherapy BEST PRACTICE ADVICE 4: Clinicians should counsel patients on the benefit of germline genetic testing and familial cancer panel testing in the pre-surgical period to inform which surgical options may be available to the patient with young adult-onset CRC BEST PRACTICE ADVICE 5: Clinicians should consider utilizing germline and somatic genetic testing results to inform chemotherapeutic strategies BEST PRACTICE ADVICE 6: Clinicians should offer hereditary CRC syndrome specific screening for CRC and extra-colonic cancers only to young adult-onset CRC patients who have a genetically or clinically diagnosed hereditary CRC syndrome. For patients with sporadic young adult-onset CRC, extra-colonic screening and CRC surveillance intervals are the same as for patients with older adult-onset CRC.

Several factors can affect the risk of recurrence after curative resection of colorectal cancer (CRC). We aimed to develop a risk model for recurrence after definitive treatment of Stage I–III CRC using data from a nationally representative database and to develop an individualized web-based risk calculator. A random sample of patients who underwent resection for Stage I–III CRC between 2006 and 2007 at Commission on Cancer (CoC) accredited centers were included. Primary data regarding first recurrence was abstracted from medical records and merged with the National Cancer Database. Multivariable cox regression analysis was used to test for factors associated with cancer recurrence, stratified by stage. Model performance was tested by c statistic and calibration plots. Hazard Ratios were utilized to develop an individualized web-based recurrence prediction tool. A total of 8249 patients from 1175 CoC centers were included. Of these, 1656 (20.1%) patients had a recurrence during 5 years of follow-up. Median time to recurrence was 16 months. The final predictive models displayed excellent discrimination and calibration with concordance indexes of 0.7. The online calculator included 12 variables, including tumor site, stage, time since surgery, and surveillance intensity. Output is displayed numerically and graphically with an icon array. Using primarily abstracted recurrence data from a random sample of patients treated for CRC at CoC accredited centers across the United States, we successfully created an individualized CRC recurrence risk assessment tool. This web-based calculator can be used by physicians and patients in shared decision making to guide management discussions. ClinicalTrials.gov Registration Number: NCT02217865.

Colorectal cancer in the young adult population is of increasing incidence and concern. Genetic predisposition and heritable syndromes contribute to this trend, but perhaps more concerning is the majority of new diagnoses that involve no traceable genetic risk factors. Prevention and early recognition, with a high suspicion in the symptomatic young adult, are critical in attenuating recent trends. Clinical management requires coordinated multidisciplinary care from diagnosis to surveillance in order to ensure appropriate management. This review provides a summary of key aspects related to colorectal cancer in adolescents and young adults, including epidemiology, biology, genetics, clinical management, and prevention.

Background Colorectal cancer in young adults is on the rise. This rise combined with delayed childbearing increases the likelihood of colorectal cancer diagnosed during pregnancy or in the postpartum period. Methods Electronic health records were used to identify individuals with colorectal cancer in pregnancy or the postpartum period from 1 August 2007 to 1 August 2019. Results Forty-two cases were identified. Median age at diagnosis was 33 years. Most (93%) were diagnosed in an advanced stage (III or IV) and had left-sided colorectal cancer tumors (81%). Molecular analysis was completed in 18 (43%) women with microsatellite status available in 40 (95%). The findings were similar to historical controls. Sixty percent were diagnosed in the postpartum period. Common presenting symptoms were rectal bleeding and abdominal pain. Conclusion Currently there is no consensus recommendation regarding how to manage colorectal cancer during pregnancy. Given the overlapping symptoms with pregnancy, patients often present with advanced disease. We encourage all health care professionals caring for pregnant women to fully evaluate women with persistent gastrointestinal symptoms to rule out colorectal cancer.

Background While the prognostic implications of positive circumferential resection margins (CRM) have been established for rectal cancer, its significance in colon cancer has not been well defined. The aim of the current study was to determine national rates for positive CRM in locally advanced colon cancer, associated factors, and survival impact. Methods The National Cancer Database was queried to identify patients with stage II-III adenocarcinoma of the colon (2004-2015). Results Positive CRM was identified in 9% of stage II and 12% of stage III patients. Factors associated with negative CRM included surgery in a high-volume facility, adequate lymph-node harvest, and negative distal/proximal margins. No difference in CRM rates was observed between surgical approaches, although having a positive CRM was significantly associated with higher conversion rates. Positive CRM was associated with significantly lower overall survival on both univariate and multivariable analysis. Conclusions Positive CRM rates exceeded 10% nationally and have an adverse impact on survival. While several tumor characteristics were identified as independent risk factors, oncologic resections and surgery at high-volume centers were associated with lower rates of positive CRM. These findings emphasize the need for process improvement initiatives targeting modifiable factors, including adoption of appropriate oncologic techniques, standardized pathology reporting, and potential neoadjuvant strategies.

Lifestyle factors related to energy balance, such as excess body weight, poor diet, and physical inactivity, are associated with risk of sporadic endometrial cancer (EC) and colorectal cancer (CRC). There are limited data on energy balance-related lifestyle factors and EC or CRC risk among individuals with Lynch syndrome, who are at extraordinarily higher risk of developing EC or CRC. We conducted a systematic review of evidence related to weight status, weight change, dietary habits, and physical activity on EC and CRC risk among individuals with Lynch syndrome. Findings are reported narratively. We searched Medline, EMBASE, CENTRAL, PubMed, and clinicaltrials.gov up to June 14(th), 2018. In total, 1,060 studies were identified and 16 were included. Three studies were related to EC and 13 to CRC. Overall, evidence suggests that weight status/weight change may not be associated with EC risk and multivitamin and folic-acid supplementation may be associated with decreased EC risk. Early-adulthood overweight/obese weight-status and adulthood weight-gain may be associated with increased CRC risk, whereas multivitamin supplementation, tea and high fruit intake, and physical activity may be associated with decreased CRC risk. Current evidence proposes that recommendations related to weight, some dietary habits, and physical activity recommended for the general public are also relevant to individuals with Lynch syndrome. More research is needed, specifically prospective cohorts and randomized controlled trials, to determine if tailored recommendations are needed among individuals with Lynch syndrome.

PURPOSE To develop recommendations for duration of adjuvant chemotherapy with a fluoropyrimidine and oxaliplatin for patients with completely resected stage III colon cancer based on the results of trials of 3 months compared with 6 months of treatment. METHODS ASCO convened an Expert Panel and conducted a systematic review of relevant studies. The guideline recommendations were based on the review of evidence by the Expert Panel. RESULTS Pooled data from the six International Duration Evaluation of Adjuvant Chemotherapy (IDEA) Collaboration randomized controlled trials comprise the evidence base for these guideline recommendations. RECOMMENDATIONS The recommendations for therapy duration apply to patients with completely resected stage III colon cancer who are being offered adjuvant chemotherapy with oxaliplatin and a fluoropyrimidine. Recommendations are informed by the findings of a recent pooled analysis of clinical trials that compared 6 months versus 3 months of oxaliplatin-based chemotherapy. For patients at a high risk of recurrence (T4 and/or N2), adjuvant chemotherapy should be offered for a duration of 6 months. For patients at a low risk of recurrence (T1, T2, or T3 and N1), either 6 months of adjuvant chemotherapy or a shorter duration of 3 months may be offered on the basis of a potential reduction in adverse events and no significant difference in disease-free survival with the 3-month regimen. In determining duration of therapy, the Expert Panel recommends a shared decision-making approach, taking into account patient characteristics, values and preferences, and other factors and including a discussion of the potential for benefit and risks of harm associated with treatment duration. Additional information is available at www.asco.org/gastrointestinal-cancer-guidelines .

Genomic profiling of colorectal cancer aims to identify actionable somatic mutations but can also discover incidental germline findings.The purpose of this study was to report the detection of pathogenic germline variants that confer heritable cancer predisposition.This was a retrospective study.The study was conducted at a tertiary-referral institution.Between 2012 and 2015, 1000 patients with advanced cancer underwent targeted exome sequencing of a 202-gene panel. The subgroup of 151 patients with advanced colorectal cancer who underwent matched tumor-normal (blood) sequencing formed our study cohort.Germline variants in 46 genes associated with hereditary cancer predisposition were classified according to a defined algorithm based on in silico predictions of pathogenicity. Patients with presumed pathogenic variants were examined for type of mutation, as well as clinical, pedigree, and clinical genetic testing data.We measured detection of pathogenic germline variants.A total of 1910 distinct germline variants were observed in 151 patients. After filtering, 15 pathogenic germline variants (9.9%) were found in 15 patients, arising from 9 genes of varying penetrance for colorectal cancer (APC (n = 2; 13%), ATM (n = 1; 6%), BRCA1 (n = 2; 13%), CDH1 (n = 2; 13%), CHEK2 (n = 4; 27%), MSH2 (n = 1; 7%), MSH6 (n = 1; 7%), NF2 (n = 1; 7%), and TP53 (n = 1; 7%)). Patients with pathogenic variants were diagnosed at a younger age than those without (median, 45 vs 52 y; p = 0.03). Of the 15 patients, 7 patients (46.7%) with variants in low/moderate- penetrant genes for colorectal cancer would likely have not been tested based on clinical and pedigree criteria, where 2 harbored clinically actionable variants (CDH1 and NF2, 28.5% of 7).This study was limited by its small sample size and advanced-stage patients.Tumor-normal sequencing can incidentally discover clinically unsuspected germline variants that confer cancer predisposition in 9.9% of patients with advanced colorectal cancer. Precision medicine should integrate clinical cancer genetics to inform and interpret the actionability of germline variants and to provide follow-up care to mutation carriers. See Video Abstract at http://links.lww.com/DCR/A906.

Objective Patients with Lynch syndrome (LS) are at markedly increased risk for colorectal cancer. It is being increasingly recognised that the immune system plays an essential role in LS tumour development, thus making an ideal target for cancer prevention. Our objective was to evaluate the safety, assess the activity and discover novel molecular pathways involved in the activity of naproxen as primary and secondary chemoprevention in patients with LS. Design We conducted a Phase Ib, placebo-controlled, randomised clinical trial of two dose levels of naproxen sodium (440 and 220 mg) administered daily for 6 months to 80 participants with LS, and a co-clinical trial using a genetically engineered mouse model of LS and patient-derived organoids (PDOs). Results Overall, the total number of adverse events was not different across treatment arms with excellent tolerance of the intervention. The level of prostaglandin E2 in the colorectal mucosa was significantly decreased after treatment with naproxen when compared with placebo. Naproxen activated different resident immune cell types without any increase in lymphoid cellularity, and changed the expression patterns of the intestinal crypt towards epithelial differentiation and stem cell regulation. Naproxen demonstrated robust chemopreventive activity in a mouse co-clinical trial and gene expression profiles induced by naproxen in humans showed perfect discrimination of mice specimens with LS and PDOs treated with naproxen and control. Conclusions Naproxen is a promising strategy for immune interception in LS. We have discovered naproxen-induced gene expression profiles for their potential use as predictive biomarkers of drug activity. Trial registration number gov Identifier: NCT02052908

Abdominoperineal resection (APR) is a procedure that removes the lower part of the colon, the rectum and the anus. The most common indication for an APR is a malignancy of the rectum or the anus. Other tumors such as pelvic sarcomas, gynecologic or genitourinary malignancies may require APR as a part of their treatment. Advanced inflammatory bowel disease may be another indication. This chapter will focus on the technical details of curative intent surgical resection of patients with rectal malignancies. The techniques described herein can be adapted for benign indications.

Background Individuals who have colorectal or endometrial cancers displaying loss of immunohistochemical staining of one or more mismatch repair proteins without an identifiable causative germline pathogenic variant have unexplained mismatch repair deficiency (UMMRD). Comprehensive germline genetic testing for Lynch syndrome (LS) includes sequencing and deletion/duplication analysis of MLH1, MSH2, MSH6, and PMS2, deletion analysis of EPCAM, and MSH2 inversion analysis. Updated genetic testing to include elements of comprehensive LS testing not previously completed could further clarify LS status in individuals with UMMRD, allowing for tailored screening guidelines for affected individuals and their family members. However, patient understanding of the potential impact of updated genetic testing for LS is unclear. This study aimed to evaluate the interest in and perceived impact of updated genetic testing among individuals with UMMRD at a tertiary academic center. Methods A survey evaluating interest in and perceived impact of updated genetic testing was mailed to 98 potential participants. Electronic health record review was completed for all individuals meeting eligibility criteria. Thirty-one individuals responded to the survey. Results Results indicate this population is highly interested in updated genetic testing with the perceived impact being primarily for family members to have appropriate genetic testing and screening. Electronic health record review indicates that clinicians have an evolving understanding of causes of UMMRD, representing a potential change in assessment of cancer risk. Conclusions Updated risk assessment and genetic counseling with a discussion of the benefits and limitations of germline and somatic genetic testing, is essential as the understanding of UMMRD and genetic testing recommendations for this population evolve.

An increasing number of studies are describing potential uses of circulating tumour DNA (ctDNA) in the care of patients with colorectal cancer. Owing to this rapidly developing area of research, the Colon and Rectal–Anal Task Forces of the United States National Cancer Institute convened a panel of multidisciplinary experts to summarize current data on the utility of ctDNA in the management of colorectal cancer and to provide guidance in promoting the efficient development and integration of this technology into clinical care. The panel focused on four key areas in which ctDNA has the potential to change clinical practice, including the detection of minimal residual disease, the management of patients with rectal cancer, monitoring responses to therapy, and tracking clonal dynamics in response to targeted therapies and other systemic treatments. The panel also provides general guidelines with relevance for ctDNA-related research efforts, irrespective of indication., The analysis of ctDNA obtained from low-volume blood samples has the potential to transform the management of patients with colorectal cancer. Nevertheless, research priorities and minimum standards for sample collection and analysis in this area are currently missing. In this Position Paper, the NCI Colon and Rectal–Anal Task Forces provide a set of recommendations designed to address these challenges and accelerate the implementation of ctDNA in the management of patients with colorectal cancer.

Introduction Women with pathogenic germline gene variants in BRCA1 and/or BRCA2 are at increased risk of developing ovarian and breast cancer. While surgical and pharmacological approaches are effective for risk-reduction, it is unknown whether lifestyle approaches such as healthful dietary habits, weight management, and physical activity may also contribute to risk-reduction. We conducted a systematic review of evidence related to dietary habits, weight status/change, and physical activity on ovarian and breast cancer risk among women with BRCA1/2 pathogenic variants. Methods We searched Medline, EMBASE, CENTRAL, PubMed, and clinicaltrials.gov up to October 3, 2019. We identified 2775 records and included 21. Results There is limited evidence related to these factors and ovarian cancer risk. For breast cancer risk, evidence suggests higher diet quality, adulthood weight-loss of ≥10 pounds, and activity during adolescence and young-adulthood may be linked with decreased risk. Higher meat intake and higher daily energy intake may be linked with increased risk. Conclusions There is not enough evidence to suggest tailored recommendations for dietary habits or weight management among women with BRCA1/2 pathogenic variants compared to the general population for ovarian and breast cancer risk-reduction, and physical activity recommendations should remain the same.

Colorectal cancer (CRC) is the third most common and lethal cancer in men and women in the United States. At presentation, a significant proportion of patients with CRC are able to undergo resection with curative intent, but up to 50% of these patients will develop recurrent disease. Fortunately, recurrence rates for both colon and rectal cancer have improved with the introduction of multimodality therapies, which include chemotherapy, chemoradiation therapy, and radiation therapy. These therapies are adjuncts to surgery and can be administered before (i.e. neoadjuvant) or after (i.e. adjuvant) surgery. This review summarizes the current evidence for the use of adjuvant and neoadjuvant therapies in colon and rectal cancer. This review contains 2 figures, 7 tables, and 77 references. Keywords: Colon cancer, rectal cancer, neoadjuvant therapy, adjuvant therapy, total neoadjuvant therapy, induction chemotherapy in rectal cancer, chemoradiation, organ preservation, non-operative management

Lynch syndrome (LS) can be strictly defined by the presence of pathogenic germline mutation in one of the four major DNA mismatch repair (MMR) genes MLH1, MSH2, MSH6, and PMS2. This deficiency in MMR function (dMMR) confers a significantly elevated lifetime risk of CRC to patients with LS, estimated to be between 15 and 70% by the age 70 depending on the variability in penetrance and expression. Despite the propensity for LS-associated CRC to arise from the proximal colon, about 15% of LS patients develop a rectal cancer. Surgical decision-making and optimal multimodality treatment planning are complex for LS-associated rectal cancer. This chapter aims to provide an overall framework as well as a series of key questions to be considered when constructing a treatment plan.

In patients with stage IV colorectal cancer (CRC), minimally invasive surgery (MIS) may offer optimal oncologic outcome with low morbidity. However, the relative benefit of MIS compared to open surgery in patients requiring multistage resections has not been evaluated.Patients who underwent totally minimally invasive (TMI) or totally open (TO) resections of CRC primary and liver metastases (CLM) in 2009-2016 were analyzed. Inverse probability of weighted adjustment by propensity score was performed before analyzing risk factors for complications and survival.The study included 43 TMI and 121 TO patients. Before and after adjustment, TMI patients had significantly less cumulated postoperative complications (41% vs. 59%, p = 0.001), blood loss (median 100 vs. 200 ml, p = 0.001) and shorter length of hospital stay (median 4.5 vs. 6.0 days, p0.001). Multivariate analysis identified TO approach vs. MIS (OR = 2.4, p0.001), major liver resection (OR = 4.4, p0.001), and multiple CLM (OR = 2.3, p = 0.001) as independent risk factors for complications. 5-year overall survival was comparable (81% vs 68%, p = 0.59).In patients with CRC undergoing multistage surgical treatment, MIS resection contributes to optimal perioperative outcomes without compromise in oncologic outcomes.

Purpose Previous studies have reported that hyperfractionated accelerated reirradiation can be used as part of multimodality treatment of locally recurrent rectal cancer with acceptable toxicity and promising outcomes. The purpose of this study was to evaluate the outcomes and toxicity of hyperfractionated accelerated reirradiation for patients with primary rectal adenocarcinoma and a history of prior pelvic radiation for other primary malignancies. Methods and materials We identified 10 patients with a prior history of pelvic radiation for other primary malignancies who were treated with hyperfractionated accelerated reirradiation for primary rectal adenocarcinoma. Radiation therapy was administered with 1.5 Gy twice daily fractions to a total dose of 39 Gy to 45Gy. Results The median follow-up time was 3.2 years (range, 0.6-9.0 years). Seven of 10 patients received surgery after reirradiation. The 3-year freedom-from-local-progression rate was 62% for all patients and 80% for patients who underwent surgery. The 3-year overall survival rate was 100%, with 3 deaths occurring at 4.7, 6.5, and 9.0 years after reirradiation. One patient had an acute Grade 3 toxicity of diarrhea, and 1 patient experienced a late Grade 3 toxicity of sacral insufficiency fracture. Conclusions Hyperfractionated accelerated reirradiation was well tolerated with promising rates of freedom from local progression and overall survival in patients with primary rectal cancer with a history of prior pelvic radiation therapy. This approach, along with concurrent chemotherapy and surgery, appears to be a viable treatment strategy for this patient population.

Greater physical activity is associated with a decrease in risk of colorectal cancer for the general population; however, little is known about its relationship with colorectal cancer risk in people with Lynch syndrome, carriers of inherited pathogenic mutations in genes affecting DNA mismatch repair (MMR). We studied a cohort of 2,042 MMR gene mutations carriers (n = 807, diagnosed with colorectal cancer), from the Colon Cancer Family Registry. Self-reported physical activity in three age-periods (20-29, 30-49 and ≥50 years) was summarized as average metabolic equivalent of task hours per week (MET-hr/week) during the age-period of cancer diagnosis or censoring (near-term exposure) and across all age-periods preceding cancer diagnosis or censoring (long-term exposure). Weighted Cox regression was used to estimate the hazard ratio (HR) and 95% confidence intervals (CI) for the association between physical activity and colorectal cancer risk. Near-term physical activity was associated with a small reduction in the risk of colorectal cancer (HR ≥35 vs.

Because of the low incidence of nongastrointestinal stromal tumor (non-GIST) spindle cell sarcomas of the colon or rectum, the clinical behavior and ideal surgical treatment of these tumors and patient outcomes are poorly defined. The purpose of this study was to characterize these tumors and to determine the best surgical approach. We identified 1056 patients with non-GIST spindle cell sarcomas of the colon or rectum (1998–2010) in the National Cancer Database and collected data for each patient that included patient and tumor characteristics, tumor site (colon vs rectum), surgery type, and outcomes. The median overall survival was significantly longer in patients with rectal tumors than in those with colon tumors ( P < 0.01). Patients with colon tumors who underwent anatomic surgical resection showed a trend toward longer median survival than those with no surgical treatment [hazard ratio (HR), 1.94; P = 0.09] or who underwent local excision (HR, 1.74; P = 0.09). Patients with rectal tumors did not benefit from anatomic surgical resection, but there was a trend favoring local excision (HR, 0.55; P = 0.06). Local sphincter-sparing procedures should be considered for rectal non-GIST tumors whenever technically feasible.

Importance Total neoadjuvant therapy (TNT) is often used to downstage locally advanced rectal cancer (LARC) and decrease locoregional relapse; however, more than one-third of patients develop recurrent metastatic disease. As such, novel combinations are needed. Objective To assess whether the addition of pembrolizumab during and after neoadjuvant chemoradiotherapy can lead to an improvement in the neoadjuvant rectal (NAR) score compared with treatment with FOLFOX (5-fluorouracil, leucovorin, and oxaliplatin) and chemoradiotherapy alone. Design, setting, and participants In this open-label, phase 2, randomized clinical trial (NRG-GI002), patients in academic and private practice settings were enrolled. Patients with stage II/III LARC with distal location (cT3-4 ≤ 5 cm from anal verge, any N), with bulky disease (any cT4 or tumor within 3 mm of mesorectal fascia), at high risk for metastatic disease (cN2), and/or who were not candidates for sphincter-sparing surgery (SSS) were stratified based on clinical tumor and nodal stages. Trial accrual opened on August 1, 2018, and ended on May 31, 2019. This intent-to-treat analysis is based on data as of August 2020. Interventions Patients were randomized (1:1) to neoadjuvant FOLFOX for 4 months and then underwent chemoradiotherapy (capecitabine with 50.4 Gy) with or without intravenous pembrolizumab administered at a dosage of 200 mg every 3 weeks for up to 6 doses before surgery. Main outcomes and measures The primary end point was the NAR score. Secondary end points included pathologic complete response (pCR) rate, SSS, disease-free survival, and overall survival. This report focuses on end points available after definitive surgery (NAR score, pCR, SSS, clinical complete response rate, margin involvement, and safety). Results A total of 185 patients (126 [68.1%] male; mean [SD] age, 55.7 [11.1] years) were randomized to the control arm (CA) (n = 95) or the pembrolizumab arm (PA) (n = 90). Of these patients, 137 were evaluable for NAR score (68 CA patients and 69 PA patients). The mean (SD) NAR score was 11.53 (12.43) for the PA patients (95% CI, 8.54-14.51) vs 14.08 (13.82) for the CA patients (95% CI, 10.74-17.43) (P = .26). The pCR rate was 31.9% in the PA vs 29.4% in the CA (P = .75). The clinical complete response rate was 13.9% in the PA vs 13.6% in the CA (P = .95). The percentage of patients who underwent SSS was 59.4% in the PA vs 71.0% in the CA (P = .15). Grade 3 to 4 adverse events were slightly increased in the PA (48.2%) vs the CA (37.3%) during chemoradiotherapy. Two deaths occurred during FOLFOX: sepsis (CA) and pneumonia (PA). No differences in radiotherapy fractions, FOLFOX, or capecitabine doses were found. Conclusions and relevance Pembrolizumab added to chemoradiotherapy as part of total neoadjuvant therapy was suggested to be safe; however, the NAR score difference does not support further study. Trial registration ClinicalTrials.gov Identifier: NCT02921256.

PURPOSE: Patients with Lynch syndrome (LS) have a significantly elevated lifetime risk of developing biliary tract cancers (BTCs) compared to the general population. However, few studies have characterized the clinical characteristics, genetic features, or long-term outcomes of mismatch-repair deficient (dMMR) cholangiocarcinomas associated with LS. METHODS: A retrospective review of a prospectively maintained Familial High-Risk GI Cancer Clinic database identified all patients with BTCs evaluated from 2006 to 2016 who carried germline mutations in MLH1, MSH2, MSH6, or PMS2. RESULTS: Eleven patients with BTCs were identified: four perihilar, four intrahepatic, one extrahepatic, one gallbladder, and one ampulla of Vater. All patients had underlying germline mutations and a personal history of a LS-associated malignancy, most commonly (63.3%) colorectal cancer. Ten (90.9%) patients were surgically explored, and margin negative resection was possible in seven (63.3%). Chemotherapy (90.9%) and/or chemoradiation (45.5%) was administered to most patients. Among the seven patients presenting with non-metastatic disease who underwent surgical resection with curative intent, the 5-year overall survival rate was 53.3%. The median overall survival for the four patients not treated with curative intent was 17.2 months. CONCLUSIONS: dMMR biliary tract cancers associated with LS are rare but long-term outcomes may be more favorable than contemporaneous cohorts of non-Lynch-associated cholangiocarcinomas. Given the emerging promise of immunotherapy for patients with dMMR malignancies, tumor testing for dMMR followed by confirmatory germline testing should be considered in patients with BTC and a personal history of other LS cancers.

Background: Select patients with rectal adenocarcinoma with metastatic disease at presentation can be cured with multimodality management. However, the optimal components and sequencing of therapy is unknown. The aim of this study is to evaluate outcomes for patients treated with chemotherapy, short course radiation therapy (SCRT) and surgical resection. Methods: Patients with newly diagnosed metastatic rectal adenocarcinoma who received SCRT from 2010–2016 were identified. All patients were evaluated by a multidisciplinary team and deemed candidates for treatment with curative intent. Overall survival (OS) and progression-free survival (PFS) were calculated using the Kaplan-Meier method. Patient, tumor and treatment characteristics were evaluated as prognostic factors using a Cox proportional hazards model. Results: Thirty-four patients were included with a median [interquartile range (IQR)] follow-up of 25 (14.75–42.25) months; 26 patients (76.5%) received definitive surgery for their rectal tumor, and 24 patients (70.6%) received definitive local management of metastatic disease. One-, 2- and 3-year OS were 97%, 86.2% and 76.0%, respectively, and 1-, 2-, and 3-year PFS were 52.1%, 22.7% and 17%, respectively. On multivariate analysis, definitive management of metastases was associated with improved OS [hazard ratio (HR) 0.03, 95% confidence interval (CI): 0.01–0.33]; P=0.003, and ≤2 months of neoadjuvant chemotherapy was associated with decreased OS (HR 11.7, 95% CI: 2.11–106; P=0.004). Conclusions: These findings suggest that SCRT can be successfully integrated into a definitive, multidisciplinary approach to metastatic rectal adenocarcinoma. Benefits to this approach include decreased time off systemic therapy as compared to standard course RT. Further study is needed to determine the optimum interval between SCRT and surgery.

Purpose: Determination of microsatellite instability (MSI) by PCR is the gold standard; however, IHC of mismatch repair (MMR) proteins is frequently performed instead. The reliability of these methods on postneoadjuvant therapy specimens is unknown. We examined the effect of neoadjuvant therapy on MSI results by PCR and IHC. Experimental design: A total of 239 colorectal cancers resected after neoadjuvant therapy were assessed for MSI with PCR and IHC. PCR and IHC results for matched paired pre- and posttreatment specimens were compared. In parallel, 2 isogenic cell lines conditioned for MMR functioning and 2 different patient-derived xenografts (PDXs) were exposed to chemotherapy, radiation, or both. We also examined whether establishment of PDXs induced MSI changes in 5 tumors. IHC and MSI were tested after treatment to assess for changes. Results: We identified paired pre- and posttreatment specimens for 37 patients: 2 with PCR only, 34 with IHC only, and 1 with both. All 3 patients with PCR had microsatellite stable pre- and posttreatment specimens. Of the 35 patients with IHC, 30 had intact MMR proteins in pre- and posttreatment specimens, 1 had equivocal MLH1 staining in the pretreatment and loss in the posttreatment specimen, and 4 had intact pretreatment MSH6 but variable posttreatment staining. In the experimental setting, no changes in MSI status were detected after treatment or tumor implantation in animals. Conclusions: Our findings show that the expression of MMR proteins, commonly MSH6, can change after neoadjuvant therapy and confirm PCR as the gold-standard test for MSI after neoadjuvant therapy. Clin Cancer Res; 23(17); 5246–54. ©2017 AACR.

Purpose: Pathologic complete response to neoadjuvant chemoradiation therapy (CRT) is associated with improved outcomes for patients with locally advanced rectal cancer (LARC). Increased response rates have been reported with higher radiation doses, but these studies often lack long-term outcome and/or toxicity data. We conducted a case-control analysis of patients with LARC who underwent definitive CRT to determine the efficacy and safety of intensified treatment with a concomitant boost (CB) approach. Methods and materials: From 1995 to 2003, a phase 2 protocol examined CRT with 5-fluorouracil and CB radiation therapy (52.5 Gy in 5 weeks) for patients with LARC. Seventy-six protocol patients were matched (case-control approach) for surgery type, tumor (T) stage, and clinical nodal (N) stage with patients who received standard dose (SD) CRT (5-fluorouracil, 45 Gy). A chart review was performed. McNemar's test and Kaplan-Meier analyses were used for statistical analysis. Results: The SD and CB groups did not differ in tumor circumferential involvement and length, but the tumors of CB patients were closer to the anal verge (4.7 vs 5.7 cm; P = .02). Although tumor downstaging was higher in the CB cohort (76% vs 51%; P < .01), pathologic complete response rates did not differ (CB, 17.1% vs SD, 15.8%, P = 1.00). The incidence of grade ≥3 radiation-related toxicities was low and similar in both groups (CB, 10% vs SD, 3%, P = .22). Postoperative (anastomotic leak, wound complications/abscess, bleeding) and late (small bowel obstruction, stricture) complication rates did not differ between the groups (P > .05). The median follow-up was 11.9 years. The 5-year local control rates were higher for CB (100.0%) compared with SD (90.0%) patients (P = .01). CB patients had higher rates of 10-year progression-free survival (71.9% vs 57.6%, P < .01) and overall survival (71.6% vs 62.4%, P = .01) compared with SD patients. Conclusions: CRT dose escalation for patients with LARC is safe and effective. The improved T-downstaging and local control observed in CB patients should encourage further dose escalation studies.

Squamous cell carcinoma (SCC) of the rectum is a rare disease with

The American Society of Colon and Rectal Surgeons is dedicated to ensuring high-quality patient care by advancing the science, prevention, and management of disorders and diseases of the colon, rectum, and anus. The Clinical Practice Guidelines Committee is composed of Society members who are chosen

Background Chemotherapy is associated with postoperative ventral incisional hernia (PVIH) after right hemicolectomy (RHC) for colon cancer, and abdominal wall closure technique may affect PVIH. We sought to identify clinical predictors of PVIH. Methods We retrospectively analyzed patients who underwent RHC for colon cancer from 2008-2018 and later developed PVIH. Time to PVIH was analyzed with Kaplan-Meier analysis, clinical predictors were identified with multivariable Cox proportional hazards modeling, and the probability of PVIH given chemotherapy and the suture technique was estimated with Bayesian analysis. Results We identified 399 patients (209 no adjuvant chemotherapy and 190 adjuvant chemotherapy), with an overall PVIH rate of 38%. The 5-year PVIH rate was 55% for adjuvant chemotherapy, compared with 38% for none (log-rank P < .05). Adjuvant chemotherapy (hazard ratio [HR] 1.65, 95% confidence interval [CI] 1.18-2.31, P < .01), age (HR .99, 95% CI .97-1.00, P < .01), body mass index (HR 1.02, 95% CI 1.00-1.04, P < .01), and neoadjuvant chemotherapy (HR 1.92, 95% CI 1.21-3.00, P < .01) were independently associated with PVIH. Postoperative ventral incisional hernia was more common overall in patients who received adjuvant chemotherapy (46% compared with 30%, P < .01). In patients who received adjuvant chemotherapy, the probability of PVIH for incision closure with #1 running looped polydioxanone was 42%, compared with 59% for incision closure with #0 single interrupted polyglactin 910. Discussion Exposure to chemotherapy increases the probability of PVIH after RHC, and non–short stitch incision closure further increases this probability, more so than age or body mass index. The suture technique deserves further study as a modifiable factor in this high-risk population.

Background Current evidence supports the curative resection of colorectal cancer and synchronous liver and lung metastases in selected patients.1,2 This video shows simultaneous left colectomy, bilobar liver resection, and lung metastasectomy via a transdiaphragmatic approach for stage IV colorectal cancer.3 PATIENT: A 57-year-old man with a stage IV colonic adenocarcinoma was considered for simultaneous resection of primary, liver, and lung metastases without thoracic incision. The tumor mutational status was KRAS, NRAS, and BRAF wild-type, and the patient underwent preoperative chemotherapy. Technique After performing a midline laparotomy, atypical liver resection of segments 8/4a was performed under the guidance of intraoperative ultrasonography and intermittent Pringle maneuver using the two-surgeon's technique. A small capsular lesion in segment 3 also was intraoperatively detected and resected. Lung metastasectomy of the right lower lobe was performed via a transdiaphragmatic approach using an endoscopic stapler. Sigmoid colectomy with transanal circular-stapled anastomosis was performed. Duration of surgery and blood loss were 358 min and 400 ml, respectively. Histopathological examination showed metastatic colonic adenocarcinoma with negative surgical margins and final stage was T3N2aM1b. The patient was discharged on postoperative day 6 without complication. He was alive and free of disease at 90-day follow-up. Conclusions Simultaneous colon, liver, and lung resection via a transdiaphragmatic approach is a feasible and safe surgical strategy in selected patients with peripheral lung metastases and favorable tumor biology.4 This surgical strategy avoids thoracic incision, multiple operations, and may reduce the healthcare costs and the recovery time to early implement postoperative therapy.

Advancements in clinical practice usually require level one evidence from clinical trials that directly compare new approaches to standard of care. While clinical trials have provided data to guide advances in practices across surgical oncology, all too often accrual to clinical trials is slower than anticipated, and once results are presented and published, adoption in clinical practice is slow. Why and how can surgeons be successfully involved with clinical trials? An expert panel discusses the basic infrastructure of clinical trials, investigator-initiated trials, the National Clinical Trials Network, and opportunities for surgeon involvement. Two national clinical trials, NSABP B-51/RTOG 1304 and PROSPECT N1048, are discussed to highlight the role of the surgical oncologist.

Background Circumferential resection margin (CRM) status is an important predictor of outcomes after rectal cancer operation, and is influenced not only by operative technique, but also by incorporation of a multidisciplinary treatment strategy. This study sought to develop a risk-adjusted quality metric based on CRM status to assess hospital-level performance for rectal cancer operation. Study Design We conducted a retrospective observational cohort study of 58,374 patients with resected stage I to III rectal cancer within 1,303 hospitals who were identified from the National Cancer Database (2010 to 2015). The number of observed cases with a positive CRM (≤ 1 mm) was divided by the risk-adjusted expected number of cases with positive CRM to form the observed-to-expected (O/E) ratio. Secondary endpoint was overall survival. Results The overall rate of CRM positivity was 15.9%. Based on the O/E ratio for 1,139 hospitals, 147 (12.9%) and 103 (9.0%) were significantly worse and better performers, respectively. The majority of hospitals (n = 570) performed as expected. Positive CRMs using criteria of 0 mm and 0.1 to 1 mm were associated with a significantly shorter 5-year overall survival of 49% and 63.5% (hazard ratio 1.67; 95% CI, 1.57 to 1.76 and hazard ratio 1.19; 95% CI, 1.12 to 1.26) than negative CRM > 1 mm of 74.1% (all p Conclusions CRM-based O/E ratio is a robust hospital-based quality measure for rectal cancer operation. It allows facilities to compare their performance with that of centers of similar characteristics and helps identify underperforming, at-risk, and high-performing centers. National quality-improvement initiatives for rectal cancer should focus on ensuring high-quality data collection and providing ready access to risk-adjusted comparative metrics.

Despite the use of neoadjuvant chemoradiation and total mesorectal excision for rectal cancer, lateral pelvic lymph node recurrence is still an important problem.This study aimed to determine the indication for lateral pelvic lymph node dissection in post neoadjuvant chemoradiation rectal cancer.This is a retrospective analysis of a prospectively collected institutional database.This study was conducted at a tertiary care cancer center from January 2006 through December 2017.Patients who had rectal cancer with suspected lateral pelvic lymph node metastasis, who underwent total mesorectal excision with lateral pelvic lymph node dissection, were included.The primary outcome measured was pathologic lateral pelvic lymph node positivity.The associations between lateral pelvic lymph node size on post-neoadjuvant chemoradiation imaging and pathologic lateral pelvic lymph node positivity and recurrence outcomes were evaluated.A total of 64 patients were analyzed. The mean lateral pelvic lymph node size before and after neoadjuvant chemoradiation was 12.6 ± 9.5 mm and 8.5 ± 5.4 mm. The minimum size of positive lateral pelvic lymph node was 5 mm on post neoadjuvant chemoradiation imaging. Among 13 (20.3%) patients who had a5 mm lateral pelvic lymph node after neoadjuvant chemoradiation, none were pathologically positive. Among 51 (79.7%) patients who had a ≥5 mm lateral pelvic lymph node after neoadjuvant chemoradiation, 33 patients (64.7%) were pathologically positive. Five-year overall survival and disease-specific survival were higher in the histologic lateral pelvic lymph node negative group than in the lateral pelvic lymph node positive group (overall survival 79.6% vs 61.8%, p = 0.122; disease-specific survival 84.5% vs 66.2%, p= 0.088). After a median 39 months of follow-up, there were no patients in the5 mm group who died of cancer. There were no lateral compartment recurrences in the entire cohort.Being a single-center retrospective study may limit generalizability.Post-neoadjuvant chemoradiation lateral pelvic lymph node size ≥5 mm was strongly associated with pathologic positivity. No patients with size5 mm had pathologically positive lymph nodes. Following lateral pelvic lymph node dissection, no patients with a positive lateral pelvic lymph node developed lateral compartment recurrence. Therefore, patients who have rectal cancer with clinical evidence of lateral pelvic lymph node metastasis and post-neoadjuvant chemoradiation lateral pelvic lymph node size ≥5 mm should be considered for lateral pelvic lymph node dissection at the time of total mesorectal excision. See Video Abstract at http://links.lww.com/DCR/B3. ¿QUIéN DEBE RECIBIR LINFADENECTOMíA PéLVICA LATERAL DESPUéS DE LA QUIMIORRADIACIóN NEOADYUVANTE?: A pesar del uso de quimiorradiación neoadyuvante y la escisión total de mesorectao para el cáncer de recto, la recurrencia en los ganglios linfáticos pélvicos laterales sigue siendo un problema importante.Determinar la indicación para la disección de los ganglios linfáticos pélvicos laterales en el cáncer rectal post quimiorradiación neoadyuvante. DISEÑO:: Análisis retrospectivo de la base de datos institucional prospectivamente recopilada.Centro de cáncer de atención terciaria, de enero de 2006 hasta diciembre de 2017.Pacientes con cáncer de recto con sospecha de metástasis en los ganglios linfáticos pélvicos laterales, que se sometieron a escisión total mesorectal con disección de los ganglios linfáticos pélvicos laterales.Positividad de ganglios linfáticos pélvicos laterales en histopatología.Se evaluaron las asociaciones entre el tamaño de los ganglios linfáticos pélvicos laterales en imagenología postquimiorradiación neoadyuvante y la positividad y recurrencia en los ganglios linfáticos pélvicos laterales en histopatología.Se analizaron un total de 64 pacientes. La media del tamaño de los ganglios linfáticos pélvicos laterales antes y después de la quimiorradiación neoadyuvante fue de 12.6 ± 9.5 mm y 8.5 ± 5.4 mm, respectivamente. El tamaño mínimo de los ganglios linfáticos pélvicos laterales positivos fue de 5 mm en las imágenes postquimiorradiación neoadyuvante. Entre 13 (20.3%) pacientes que tenían5 mm de ganglio linfático lateral pélvico después de la quimiorradiación neoadyuvante; ninguno fue positivo en histopatología. Entre 51 (79.7%) pacientes con ganglio linfático pélvico lateral ≥ 5 mm después de la quimiorradiación neoadyuvante; 33 pacientes (64.7%) fueron positivos en histopatología. La supervivencia general a 5 años y la supervivencia específica de la enfermedad fueron mayores en el grupo histológico de ganglio linfático pélvico lateral negativo que en el grupo de ganglio linfático pélvico lateral positivo (Supervivencia general 79.6% vs 61.8%, p = 0.122; Supervivencia específica de la enfermedad 84.5% vs 66.2%, p = 0.088). Después de una mediana de seguimiento de 39 meses, no hubo pacientes en el grupo de5 mm que hayan fallecido por cáncer. No hubo recurrencias en el compartimento lateral en toda la cohorte.Al ser un estudio retrospectivo en un solo centro puede limitar la generalización.El tamaño de los ganglios linfáticos pélvicos laterales postquimiorradiación neoadyuvante ≥ 5 mm se asoció fuertemente con la positividad histopatológica. Ningún paciente con tamaño5 mm tuvo ganglios linfáticos histopatológicamente positivos. Después de la disección de los ganglios linfáticos pélvicos laterales, ningún paciente con ganglios linfáticos pélvicos laterales positivos desarrolló recurrencia del compartimiento lateral. Por lo tanto, los pacientes con cáncer rectal con evidencia clínica de metástasis en los ganglios linfáticos pélvicos laterales y tamaño de ganglios linfáticos pélvicos laterales postquimiorradiación neoadyuvante ≥ 5 mm deben considerarse para disección de los ganglios linfáticos pélvicos laterales en el momento de la escisión total de mesorrecto. Vea el Abstract en video en http://links.lww.com/DCR/B3.

Currently, colorectal cancers accounted for the second-highest number of cancer deaths in the US. Hereditary syndromes, strong family history, and inflammatory bowel disease are all conditions that confer predisposition risks. In hereditary syndromes, screening must be more frequent and start earlier. With familial risk, screening should depend on the age of cancer onset and number of affected relatives. For inflammatory bowel disease, surveillance should depend on duration, severity, and extent of colitis.

Background Magnetic resonance imaging (MRI) is essential for the multidisciplinary treatment of rectal cancer. However, baseline experience of surgical residents with MRI is unknown. Therefore, a needs assessment survey was conducted to examine confidence with pelvic MRI for residents entering Complex General Surgical Oncology (CSGO) fellowships. Methods A multi-institutional survey evaluated incoming CGSO fellows’ experience with pelvic MRI for rectal cancer in residency. Additionally, confidence was assessed for essential components of pelvic MRI including T- and N-stage, circumferential resection margin (CRM), extramural venous invasion (EMVI), and pelvic anatomy. Results Of the twenty-four incoming fellows who completed the survey (response rate = 44%), 20 reported frequent use of pelvic MRI for rectal cancer in residency, but 16 reported rarely/never interpreting images themselves for staging or operative planning. Most respondents reported low confidence for T-stage, N-stage, CRM, EMVI, as well as pelvic anatomy, particularly for lateral and posterior pelvis. Conclusions The development of a pelvic MRI curriculum for residents entering CGSO fellowships could enhance their clinical training in the multidisciplinary management of patients with rectal cancer.

Colorectal cancer etiology is multifactorial, with genetic and environmental factors contributing to various degrees in each individual patient. Underlying genetic and molecular pathways produce unique subsets of colorectal cancers that have distinct but somewhat overlapping phenotypes: chromosomal instability, microsatellite instability, and DNA hypermethylation. These changes are manifest in both sporadic cancers and in hereditary syndromes. Clinicians must be aware of the various underlying genetic and molecular causes of disease as it impacts clinical management, particularly in the hereditary syndromes. This chapter summarizes the main genetic causes of colorectal cancer and the clinical presentation and management of the hereditary colorectal cancer syndromes.

Surgery is the mainstay therapy for rectal cancer. Currently, standard of care includes neoadjuvant and adjuvant treatments for stage II (T3-4, node-negative disease with tumor penetration through the muscle wall) or stage III (node- positive disease without distant metastasis) due to the relatively high risk of locoregional relapse [1]. However, over the past several years, the management algorithm of rectal cancer has become more complex. With the realization that a selected subset of rectal cancers can completely regress after neoadjuvant therapy (NAT), the concept of organ preservation in the context of an apparent clinical complete response has emerged, coupled with the advent of a watch and wait paradigm as well as the concepts of total neoadjuvant therapy (TNT) or treatment intensification programs.

e15601 Background: We evaluated demographic, treatment, and survival outcomes of adults age 18 to 49 years treated at our institution with long course chemoradiotherapy (CRT) followed by total mesorectal excision (TME) for locally advanced rectal cancer. Additionally, we compared outcomes between those age < 45 vs. > 45 years. Methods: The records of 219 patients diagnosed with non-metastatic, clinical T3, T4, or node positive rectal adenocarcinoma and treated between April 2000 and November 2017 were reviewed for age, sex, and presenting symptoms; clinical stage and microsatellite stable (MSS)/DNA mismatch repair (MMR) proficiency status; treatments delivered and sequence; pathologic response to pre-operative therapies; and the development of locoregional recurrence (LRR), distant metastasis (DM), and secondary pelvic malignancy. The Kaplan-Meier method and Log-Rank test were used to calculate and compare disease-free survival (DFS) and overall survival (OS) rates from the date of TME. Results: The median age at diagnosis was 44 years (range 19-49) and there was no sex predominance. Rectal bleeding was the most common presenting symptom (91%), with a median time to diagnosis of 5 months. Clinical tumor/nodal categories were T1-2 in 4%, T3 in 87%, T4 in 7%, N0 in 17%, and N1–2 in 80% of patients. MSS/MMR proficient disease was identified in 95% of tumors with status reported (n = 170). CRT followed by TME and post-operative chemotherapy was the most frequent treatment sequence (n = 196), with capecitabine (n = 176) and FOLFOX (n = 115) as the predominant concurrent and post-operative chemotherapies, respectively. Pathologic complete response at both primary and nodal sites occurred in 15% of all cases and 16% of MSS/MMR proficient cases. There was no difference in sex, tumor category, nodal category, MSS/MMR proficiency status, or pathologic complete response, by age ( < 45 years [n = 111] vs. > 45 years [n = 108]). At a median DFS follow-up time of 5.0 years, there were 11 LRR, 40 DM (including 11 DM detected prior to/at time of TME), and 1 synchronous presentation of LRR and DM. The 5-year rate of DFS was 70.4% for age < 45 years and 85.3% for age > 45 years ( P = 0.02). At an OS median follow-up time of 7.5 years, there were 38 deaths. The 5-year rate of OS was 87.7% for age < 45 years and 94.4% for age > 45 years ( P = 0.126). Two patients developed non-rectal pelvic malignancies. Conclusions: The outcomes reported here from one of the largest single-institution series for young-onset, locally advanced rectal cancer could serve as a benchmark to evaluate newer treatment approaches. Rectal bleeding was the leading presenting symptom, with approximately half-year delay from development of symptoms to diagnosis. Most tumors were MSS/MMR proficient. At 5 years’ follow-up time, the DFS rate was lower for patients age < 45 years when compared to those > 45 years. Secondary pelvic malignancies were a rare occurrence.

3549 Background: Strategies to detect and prevent young-onset colorectal cancer (YOCRC, diagnosed under age 50) are critical. Established high-risk screening guidelines (SGs) aim to detect/prevent YOCRCs arising from hereditary syndromes. For non-hereditary YOCRCs, average-risk screening is being considered at an earlier age, but family history (FH)-based increased-risk screening has been poorly studied. We aimed to define the proportion of non-hereditary YOCRC with a FH, and to determine whether existing SGs could have detected/prevented these cases. Methods: 394 consecutive YOCRC patients presenting for surgical resection were reviewed for tumor MMR status, pedigree and genetic testing. Those with known/suspected hereditary syndrome (by phenotype, MMR status, and/or germline mutation) were excluded (N = 65). Pedigrees (N = 329) were analyzed for first- or second-degree relatives (FDR, SDR) with CRC and the ages of diagnosis. The gap between the recommended age for FH-based CRC screening and the age of YOCRC diagnosis was calculated. Results: 89 (27%) non-hereditary YOCRC patients had a FH of CRC. The median age of diagnosis was 45; the tumors were mostly from the distal colon (22%) and rectum (60%), and stage III (48%) and IV (27%). Twenty-one (24%) patients had 22 FDRs with CRCs diagnosed at age 64 (median); and 71 (80%) patients had 92 SDRs with CRCs diagnosed at age 65 (median). Thirteen (15%) had a FH of YOCRC. The existing SGs consider 39 patients (44%) at increased-risk, and the remaining, average-risk (Table). Screening would have begun prior to the YOCRC diagnoses in 28 (31% [or 46, 52%]) patients. But YOCRC diagnosis preceded the recommended screening age in the remaining 61(69% [or 43, 48%]) patients by a median of 5.3 [or 3.9] years (Table). Conclusions: FH is found in 27% of the non-hereditary YOCRC patients; 15% has a FH of YOCRC. In nearly half of the patients, YOCRC was diagnosed several years earlier than the recommended age for FH-based screening, even assuming perfect SG adoption and starting average risk screening at age 45. Refining existing FH-based SGs can potentially be impactful.[Table: see text]

2520 Background: Pembrolizumab (Pembro), anti-PD1 therapy, is FDA approved for refractory microsatellite instability high (MSI-H)/deficient mismatch repair (dMMR) advanced/metastatic solid tumors. The robust activity of anti-PD1 therapy in these tumors argues for a neoadjuvant organ-sparing approach. However, the role of anti-PD1 monotherapy in the neoadjuvant setting is unknown. Methods: This is a phase 2 open-label, single center trial (NCT04082572) of MSI-H/dMMR non-metastatic solid tumors with localized unresectable or high risk resectable (defined as ≥ 20% recurrence) with measurable disease per RECISTv1.1 and ECOG PS 0/1. Treatment is Pembro 200mg every 3 wks for 8 cycles (6 months) followed by surgical resection with option to continue therapy for 18 cycles (12 months) followed by observation. First restaging is at 6 wks and includes baseline and 3-week 70-gene ctDNA assessment. To continue on study, patients are required to have PR/CR, SD with tumor shrinkage or SD with decline in ctDNA [highest variant allele frequency (VAF) baseline mutation]. The co-primary endpoints are safety and pathological complete response (pCR). Key secondary endpoints are response rate and organ-sparing at one year for patients who declined surgery. Results: Between 12/2019 and 2/2021, 32 pts were enrolled and treated. Enrolment goal of 35 anticipated to be met by 4/2021. Baseline characteristics included 13 females, median age of 63 yrs (range 26 - 91), Lynch syndrome in 12 pts, BRAF V600E mutation in 11 pts. Tumor type included 24 CRC and 8 non-CRC (1 endometrial, 1 gastric, 1 meningeal, 2 duodenal, 1 ampullary, 2 pancreatic). At baseline disease was resectable in 23 (72%). Among 30 evaluable pts, best overall response rate was 77%: 30% CR (n = 9), 47% PR (n = 14), 20% SD (n = 6), 3% PD (n = 1). Only one pt progressed after initial SD of -18%. Median follow-up is 6.1 months (range 0.1 - 14). Among the 6 (20%) pts who underwent surgery, pCR was seen in 3 (50%). A non-operative approach (pembro for 12 months) has been chosen in 15 pts and 1-year organ-sparing was seen in 2/2 evaluable pts. Treatment-related grade 3/4 immune adverse events (TRAE) were seen in 3 (9%) pts: grade 3 immune hepatitis (2) and grade 3 type 1 diabetes (1). Baseline ctDNA was positive in 17 (53%) pts with a median of 4 mutations per pt (1 - 35) and median highest VAF of 0.9% (range 0.3% to 38.2%). Among 26 pts with successful tumor tissue testing, median tumor mutations were 10.5, range 1 to 21 (Oncomine 134 gene panel). ctDNA decline at 3 weeks was seen in 14/17 (82%) patients. Luminal disease was present in 24 pts with endoscopic response of: CR in 13 (54%), major response 1, pending follow-up evaluation 6, not evaluated 3, and no response in 1. Conclusions: Neoadjuvant pembrolizumab is safe with encouraging clinical activity and this data suggests that a non-operative management for dMMR/MSI-H localized solid tumors should receive further investigation. Clinical trial information: NCT04082572.

8 Background: This NCTN multi-arm randomized phase II modular clinical trial platform utilizes TNT with parallel EAs in LARC. EAs are not intended for direct comparison, but rather to test a variety of sensitizers or hypotheses in a consistent and homogenous high-risk pt population with correlative biomarkers. Here we report the primary and available secondary endpoints (EPs). Methods: Stage II/III LARC pts (with ONE or more of the following: distal location [cT3-4 ≤5cm from anal verge, any N]; bulky [any cT4 or tumor within 3mm of mesorectal fascia]; high risk for metastatic disease [cN2]; or not a sphincter-sparing surgery [SSS] candidate) were randomized to neoadjuvant FOLFOX x 4mo → chemoRT (capecitabine with 50.4Gy +/- pembrolizumab 200mg IV Q3 wks x 6 doses) → surgery 8-12 wks following last dose of radiotherapy. Primary EP: Improvement in Neoadjuvant Rectal Cancer (NAR) score for EA v control potentially representing a 3-4% absolute OS improvement. Secondary EPs: Comparisons of OS, DFS, toxicity, pCR, cCR, therapy completion, negative surgical margins, sphincter sparing surgery (SSS), and exploratory assessments of molecular and radiographic predictors of response and distant failure. Binary EPs compared by Fisher’s exact test. Reported p-values are two-sided. Results: From 8/2018-5/2019, 185 pts were randomized to control (n=95) or pembrolizumab (n= 90). Baseline characteristics were relatively well balanced. 137 pts were evaluable for NAR (68 control, 69 pembrolizumab). Mean NAR was 14.08 for control (95% CI: 10.7-17.4) v 11.53 for pembrolizumab (CI: 8.5-14.6) (p=0.26). pCR=29.4% v 31.9% (p=0.75); cCR=13.6% v 13.9% (p=0.95); and SSS=71.0% v 59.4% (p=0.15). The side effects on Arm 3 were consistent with both CRT and pembrolizumab safety profile. Grade 3/4 AEs were slightly increased on the pembrolizumab arm during and after CRT (48.2 v 37.3%). There were 2 deaths during FOLFOX, one on the control arm due to sepsis; the other on the EA due to pneumonia. There were no statistically significant differences in RT (fractions, dose, boost fractions, or boost dose), FOLFOX or capecitabine doses. Conclusions: Pembrolizumab added to chemoRT as part of TNT was safe and without unexpected short-term toxicities but failed to improve the NAR score. The secondary endpoints including PFS and OS have not been reached. Correlative analysis for both T-cell and myeloid cell populations in the tissue and blood in addition to comprehensive cytokine analysis is ongoing. NCT02921256. Support: U10CA180868, -180822; UG1-189867; U24-196067. Clinical trial information: NCT02921256.

13 Background: Non-Hispanic Black patients (NHBs) and low socioeconomic status (SES) non-Hispanic White patients (NHWs) have worse cancer outcomes. In most cancers, the relative importance of treatment disparities vs. other pathways are undefined. We estimated the proportion of overall survival (OS) disparities mediated by treatment disparities in NHBs and NHWs with stage IV CRC. Methods: We queried the National Cancer Database for NHBs and NHBs (aged 18-80) diagnosed with stage IV CRC in 2010-16. Zip code SES was defined as low (quartile 1 income and education), high (quartile 4 income and education), and middle. Exclusions were missing SES, chemotherapy contraindications/refusal, unknown treatment, and < 60 days follow-up. From available variables, we examined 3 plausible treatment mediators of OS: chemotherapy, metastatectomy, and treatment at > 1 CoC facility. Primary tumor resection was not analyzed to avoid immortal time bias. We used inverse odds ratio weighting (IORW) to estimate the proportion mediated ( PM) while adjusting for sex, age, cancer history, comorbidities, year, tumor location, grade, LVI, CEA, and KRAS status. Results: Among 70,773 patients, the rate of low SES was 3.6-fold higher among NHBs than NHWs. There were graded associations between higher SES and rates of each mediator (Cuzick trend tests, all p ⩽ 0.01). Furthermore, low and middle SES NHB and NHWs all had significantly lower rates of each mediator than high SES NHWs (Table, part A). 5-yr OS ranged from 14.5% in low SES NHBs to 21.9% in high SES NHWs. Low and middle SES NHWs and all NHBs had shorter adjusted OS than high SES NHWs (Table, part B). PMs were higher for low and middle SES NHBs vs. NHWs (27-28% vs. 19-22%). PMs were largest for metastasectomy (9.9-16.1%) and smallest for chemotherapy (5.0-7.9%). Conclusions: Treatment disparities mediate at least 20-30% of OS disparities in NHBs and NHWs with stage IV CRC. These estimates may represent the lower bound of true PMs since many aspects of treatment quality were unmeasured. These findings imply that policies addressing treatment disparities are projected to partially close survival gaps. [Table: see text]