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Background: Infection with SARS-CoV-2 has led to a global pandemic and has significantly impacted the care of cancer patients. Breast cancer patients receiving active systemic therapy need protection against COVID19 but the efficacy of vaccines in this population is unknown. Although specific biomarkers associated with protection from SARS-CoV-2 infection have yet to be identified, measurement of serum antibody activity is generally accepted as a surrogate of in vivo humoral response to vaccine. This study evaluates the efficiency and durability of binding antibodies to SARS-CoV-2 spike (S) protein in response to COVID19 vaccine in breast cancer patients receiving systemic treatment. Methods: Breast cancer patients, who were unvaccinated, partially or fully vaccinated with Pfizer-BioNTech BNT162b2 (PF), Moderna mRNA-1273 (Mod) or Johnson & Johnson AD26.COV2.S (J&J) were enrolled in this prospective longitudinal study. Eligible patients were on systemic treatment with cytotoxic chemotherapy, chemotherapy plus a checkpoint inhibitor (CPI), CPI alone or a CDK 4/6 inhibitor. Longitudinal blood samples are being collected at baseline, prior to vaccination in unvaccinated patients (T0), 2 weeks after the first vaccine dose and before the second dose for the mRNA vaccines (T1), 1 month (T2), 3 months (T3), 6 months (T4) and 12 month post vaccination. For J&J, there was no T1 timepoint. Roche Elecsys® Anti-SARS-CoV-2 S receptor binding domain (RBD) antibody immunoassay was used to measure antibody titers (range 0.4 to 250 U/mL). Cut points of N% Seropositive (>0.8 U/mL)Mean Antibody Levels (U/mL)T0T1T2T3T0T1T2T3All subjects7510789810012.6102.3204.4214.6Chemotherapy50577961003.3105.6200.0250CDK 4/6 inhibitors15257510010013.786.8234.7205.8CPI + Chemotherapy82583100NA*62.8121.4177.5NA*CPI therapy20100100NA*0.46.82250NA*CPI=Checkpoint Inhibitors; *Timepoint for longitudinal samples not reached Citation Format: Cory Bivona, Kevin Li, Priyanka Sharma, Jianghua He, Grace Martin, Andrew K Godwin, Anthony Rooney, Stephen Williamson, Gary Doolittle, Weijing Sun, Bruce F Kimler, Anne P O'Dea, Lauren E Nye, Joseph P McGuirk, Ziyan Pessetto, Lisa Haney, Nicole Balmaceda, Laura Mitchell, Karissa Finke, Maggie Nelson, Dinesh Pal Mudaranthakam, Natalie Streeter, Stephanie Lafaver, Jaimie Heldstab, Qamar J Khan. Immunogenicity of SARS-CoV-2 vaccination in subjects on active treatment for breast cancer [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P4-10-03.

4047 Background: Surgical rection is the only potentially curative intervention for locally advanced adenocarcinoma of esophagus, GEJ and stomach. Results from various studies have demonstrated the benefits of perioperative treatment including neoadjuvant and adjuvant chemotherapy or chemoradiation, however, there is lack of universally accepted standard. Recent data demonstrated the benefit of immune checkpoint inhibitor in adjuvant setting in patients who had pre-operative chemoradiation. This single arm phase 2 trial is aimed to evaluate efficacy and safety of pembrolizumab, an immune checkpoint inhibitor, in combination with mFOLFOX in patients with potentially resectable adenocarcinoma of distal esophagus, GEJ and stomach. The primary objective is pathological response rate (ypRR with tumor regression score, TRS ≤ 2). Methods: Newly diagnosed locally advanced (T1N1-3M0 or T2-3NanyM0), potentially resectable adenocarcinoma of distal esophagus, GEJ and stomach by PET, EUS, CT C/A/P and staging laparoscopy were treated with pre-operative mFOLFOX6 (oxaliplatin 85mg/m2, Leucovorin 400mg/m2, 5-FU bolus 400mg/m2, and 5-FU 2400mg/m2 infusion every 2 weeks) for 4 cycles and pembrolizumab (200 mg IV q3week) for 3 cycles. Patients with no evidence of metastatic disease by PET and CT C/A/P who are eligible for resection underwent surgery. Post-operative treatment consisted of 4 cycles of mFOLFOX and 13 cycles of pembrolizumab 4-8 weeks postoperatively. Results: Up to 2/10/2021, all 37 patients eligible for the study finished preoperative treatment. 27 had curative intended operations, and all had R0 resection. 5 of 27 (19%) achieved ypCR and 6/27 (22 %) with regression score of 0 in the primary cancer. All except 2 patients (25/27, 93%) had shown pathologic response to the treatment with TRS ≤ 2. 21 patients completed all planned treatment with an average follow-up of 27 months. 2 patients had recurrence/metastatic disease (at 9 and 10 months from the enrollment) with 1 died at 23 months, and the other is still alive at 20 month. The rest patients (19/21) are all free of disease. G3/4 toxicities were reported in 21 of all 37 treated patients. There were no unexpected toxicities. Conclusions: The combination of mFOLFOX and pembrolizumab as peri-operative (pre- and post-operative) therapy in patients with locally advanced adenocarcinoma of distal esophagus, GEJ and stomach is safe. The preliminary benefit data are very encouraging with ypRR of 93%, ypCR of 19 %, and the long-time survival. The data support the combination of chemotherapy and Immune checkpoint inhibitor at perioperative setting. In addition, the data supports the staging laparoscopy for peritoneal disease assessment as the standard in resctacbility evaluation. Clinical trial information: NCT03488667.

Biliary tract cancers are rare, aggressive neoplasms. Most patients present with advanced/unresectable or metastatic disease at diagnosis, and no second-line regimen has demonstrated clinical benefit. This was a phase 2 study evaluating the efficacy and safety of regorafenib in patients who had advanced/unresectable or metastatic disease after receiving standard therapy.In this single arm-study, patients with advanced/unresectable or metastatic biliary tract cancer who failed at least 1 line of systemic chemotherapy received regorafenib once daily on a schedule of 21-days on/7-days off in a 28-day cycle. Patients initially received a standard 160 mg dose. After toxicity assessments in the first 3 patients, the dose was reduced to 120 mg for subsequent patients, as preplanned. The primary endpoint was progression-free survival (PFS). Secondary objectives included overall survival (OS), the objective response rate, and the disease control rate.Forty-three patients received at least 1 dose of regorafenib, and 34 patients who received at least 1 cycle of treatment were evaluable for tumor response. The median PFS was 15.6 weeks (90% confidence interval, 12.9-24.7 weeks), and the median OS was 31.8 weeks (90% confidence interval, 13.3-74.3 weeks), with survival rates 40% at 12 months and 32% at 18 months. A partial response was achieved in 5 patients (11%), and 19 had stable disease (44%), for a disease control rate of 56%. The toxicity profile was as expected, with grade 3 and 4 adverse events reported in 40% of patients. The most common toxicities were hypophosphatemia (40%), hyperbilirubinemia (26%), hypertension (23%), and hand-foot skin reaction (7%).The current results suggest promising efficacy of regorafenib in patients with chemotherapy-refractory, advanced/metastatic biliary tract cancer, warranting further studies to confirm its clinical efficacy. There is a clear unmet need for effective therapies in patients who have advanced and metastatic biliary tract cancer.

Background The SARS–CoV-2 pandemic has assaulted all aspects of daily life. Medical professionals in oncology face additional challenges with balancing prompt cancer diagnosis and urgent treatment against potential COVID-19 exposure risk in these high-risk patients. We designed this prospective freewill study to offer testing for SAR2-CoV-2 viral RNA and/or anti-COVID-19, respectively in asymptomatic medical and research staff who work in direct contact with cancer patients. The overall goal was to evaluate the prevalence of infection in this group of asymptomatic healthcare providers to reduce exposure of cancer patients to asymptomatic staff. Methods Asymptomatic medical and research staff who work in direct contact with cancer patients were asked to voluntarily be tested for either SARS–CoV-2 viral RNA or antibodies or both. Either NP swabs and/or blood samples (EDTA tube) were collected. Tests are performed at Sinochips Kansas LLC, Sinochips Diagnostics (CLIA number:17D2176068, CAP number: 8709463). The PCR test is performed with FDA authorized 2019-Novel Coronavirus (2019-nCoV) Real-Time RT-PCR Diagnostic Panel EUA. The Elecsys® Anti-SARS-CoV-2 (Roche Diagnostics) immunoassay was used to qualitative detection of antibodies to SARS-CoV-2 in human plasma. Results From 06/18/2020 to 12/18/2020, 861 participated in the study. 1095 tests were completed for SAR2-CoV-2 virus infection, and 918 were completed for antibody. Amount participants, 530 had both virus and antibody tested. 235 were tested more than once for viral infection and 166 were tested more than once for the antibody. Median age of participants was 39 years (IQR 32-51 years). Among these 84.7% were females, 84.4% white, 6.7% African American, 4.8% Asian and 84.7% non-Hispanic. The cumulative incidence of a positive test for the virus was 2.2% (16/712), and for the antibody test was 3.8% (26/679). 5 had both viral and antibody tests positive, with an average time of 4.1 weeks from viral testing positivity to detectable antibody among 3 cases and 2 cases with both viral infection and antibody detected at same time. There were 3 cases virus was detected more than once after turning positive. 2 remained positive at 16 and 22 days after initial test and one turned negative at 36 days as of last follow up. There were 7 cases where the antibody was tested more than once after turning positive and all 7 remained positive as of last follow up (range 7-103 days). Conclusion Prospective voluntary testing in asymptomatic medical and research staff who work in direct contact with cancer patients was feasible and resulted in identification of asymptomatic carriers who then placed in quarantine, thereby limiting exposure to cancer patients. Medical and research staff who work with cancer patients are general very cautious and the frequency of infections were significantly lower than general society. In addition, it seems that 1) virus and antibody may co-exist in the same person after exposure, and 2) the antibody may last for a relatively long time. Citation Format: Weijing Sun, Andrew K. Godwin, Kathan Mehta, Natalie Streeter, Elizabeth Wulff-Burchfield, Anup Kasi, Tara L. Lin, Joaquina Baranda, Joseph McGuirk, Ziyan Pessetto, Adam Pessetto, B.J. Broome, Terry Tsue, Roy Jensen. Prospective voluntary SARS-CoV-2 virus and anti-COVID-19 antibody tests in asymptomatic medical and research staff who work in direct contact with cancer patients: A single center study [abstract]. In: Proceedings of the AACR Virtual Meeting: COVID-19 and Cancer; 2021 Feb 3-5. Philadelphia (PA): AACR; Clin Cancer Res 2021;27(6_Suppl):Abstract nr P13.

Background: The oncology community faces unprecedented challenges in balancing a delay in cancer treatment against the risk for a potential COVID-19 infection and associated complications. An early retrospective analysis reported that cancer patients with COVID-19 infection have a much higher death rate than those infected but without a cancer diagnosis, likely because of their immunocompromised disease from cancer and treatment. Even though COVID-19 is known to have a long incubation period (~14 days), there were no clear guidelines for screening asymptomatic cancer patients who are planning to have and having antitumor treatment as of April 2020. Methods: We developed a protocol to screen asymptomatic cancer patients for COVID-19 who are scheduled to receive cancer-directed treatment (i.e., chemotherapy, targeted therapy, immunotherapy, anticancer monoclonal antibody, endocrine therapy, or investigational agent). The protocol was developed and activated within 2 weeks through the Cancer Center Investigator Initiated Trial Program. FDA-authorized CDC 2019-Novel Coronavirus (2019-nCoV) Real-Time RT-PCR Diagnostic Panel EUA kit was performed at Sinochips Diagnostics. The primary objective was to determine COVID-19 status in participants prior to initiating anticancer treatment. The secondary objective was to evaluate COVID-19 related adverse events (AEs) in recovered COVID-19-positive participants for 30 days after initiation of anticancer therapy. Results: We enrolled 507 patients and tested for COVID-19 from 4/28/20 to 5/8/20 through coordinated efforts within the CTO and Biospecimen Repository Core Facility. The research study was stopped when the KU Health System was able to test this population as standard of care. Median age was 65 years, 110 patients (22%) were aged 75 years or older, and 274 (54%) patients were female. 387 patients (76.3%) were Caucasians, 35 (6.9%) African American, 7 (1.4%) Asian, and 437 (86.2%) non-Hispanic. Based on the catchment of zip codes, 7% of tested patients came from more than 60 miles and 1.6% from more than 100 miles. Zero patients had a positive COVID-19 test. Conclusions: The prevalence of COVID19 in asymptomatic cancer patients is low, likely because of good compliance with the social distance policy. Screening for COVID19 may help reduce AEs related to COVID-19 in patients receiving cancer-directed treatment. Studying COVID-19 test results in a larger patient pool is warranted. A similar study to test asymptomatic patient-facing oncology staff is pending. Citation Format: Kathan D. Mehta, Elizabeth Wulf-Burchfield, Natalie Streeter, Anup Kasi, Adam H. AlDouri, Roy Jensen, Andrew K. Godwin, Terry Tsue, Weijing Sun. A prospective testing SARS-Cov-2/COVID-19 in cancer patients with antitumor treatment [abstract]. In: Proceedings of the AACR Virtual Meeting: COVID-19 and Cancer; 2020 Jul 20-22. Philadelphia (PA): AACR; Clin Cancer Res 2020;26(18_Suppl):Abstract nr PO-043.

Background: There is insufficient evidence to support clinical decision-making for oncology patients diagnosed with COVID-19 due to the limited studies focusing on factors affecting COVID-19-associated disease severity/death in cancer patients. Methods: We retrospectively analyzed data from KU Cancer Center to assess demographic/clinical characteristics and ferritin levels of 40 cancer patients with a confirmed COVID19 diagnosis by viral RNA detection in a nasopharyngeal swab between 3/1/20 through 6/9/20. Chi square test and Mann-Whitney U test were used to identify whether demographic/clinical characteristics and ferritin were associated with COVID-19 severity/death. Results: Median age was 59.5 years, 16 (40%) were aged 65 years or older, and 18 (45%) patients were male. 31 (77.5%) were non-Hispanic, 21 (52%) were Caucasians, 11 (27%) were African Americans, and 21 (52.5%) were current/former smokers. 14 (35%) were obese. Breast cancer n=9 (22.5%) was the most prevalent malignancy. 28 (70%) had ECOG of 0/1. 27 (67.5%) were on active anticancer treatment, and 13 (32.5%) had active (measurable) cancer. 12 (30%) had recent surgery. 6 (15%) were asymptomatic and 34 (85%) were symptomatic. Fever (47.5%), cough (57.5%), productive cough (50%), and shortness of breath (47.5%) were the most common symptoms. At analysis (June 9, 2020), 3 (7.5%) patients had died. 8 (38.1%) had mild/moderate COVID-19 illness and 13 (61.9%) had severe illness (ICU admission, intubation, death). Patients with mild/moderate illness were significantly younger (median age 56.5 years) vs. those with severe illness (median age 67.5 years), p=0.02. Sex, race and ethnicity, obesity, ECOG, cancer type, active cancer treatment, and recent surgery were not associated with COVID-19 severity. However, productive cough (p=0.01) and shortness of breath (p=0.006) were associated with COVID-19 severity. In 19 patients with available ferritin levels, asymptomatic patients (n=2) had a significantly lower ferritin (median 68.5 NG/ML) vs. symptomatic (n=17), who had higher ferritin (median 422 NG/ML) p=0.04. Conclusions: Age was associated with an increased risk of COVID-19-related disease severity/death in cancer patients. This may possibly reflect the effects of more advanced malignant disease, anticancer treatment, and comorbidities on the impact of this infection. Ferritin levels appear to have a role in screening and monitoring for COVID-19 infection in cancer patients. Hence, our findings warrant validation in a larger cohort. A prospective study is under way at the University of Kansas Cancer Center to validate the factors associated with COVID-19-related disease severity/death in cancer patients. Citation Format: Anup Kasi, Elizabeth Wulf-Burchfield, Natalie Streeter, Stephen Jackson, David Streeter, Eric Crowder, Kathan Mehta, Weijing Sun. Preliminary analysis of factors associated with COVID-19-related disease severity in cancer patients: University of Kansas Cancer Center experience [abstract]. In: Proceedings of the AACR Virtual Meeting: COVID-19 and Cancer; 2020 Jul 20-22. Philadelphia (PA): AACR; Clin Cancer Res 2020;26(18_Suppl):Abstract nr PO-082.

4081 Background: Biliary adenocarcinoma/cholangiocarcinoma is a rare but aggressive neoplasm. Most patients present with unresectable or metastatic disease with 5-year survival rate ~5%. No second-line regimen has demonstrated clinical benefit in this disease. Regorafenib is an oral multi-kinase inhibitor with potent antitumor activity. This single arm phase II study evaluates the efficacy and safety of regorafenib as a single agent in advanced or metastatic biliary carcinoma/cholangiocarcinoma pts who failed systemic chemotherapy. Methods: Patients with ECOG PS 0-1and adequate liver, kidney and bone marrow function were given regorafenib orally once daily, 21 days on and 7 days off in a 28-day cycle. The initial dose of 160 mg was given to the first 3 patients. After toxicity assessment, the dose was reduced to 120 mg for the subsequent pts. The primary endpoint is PFS with the null hypotheses of 2.0 months, and median PFS ≥3.5 months as evidence of the study drug activity (α = 0.10, 80% power). Secondary objectives include OS, RR, and DCR. Results: Thirty-seven patients received at least one dose of regorafenib, of whom 28 were evaluable for efficacy. All had previous gemcitabine/cisplatin treatment. The mean age was 62.5 (34.5-82.8) with 17 (46%) females. PR was achieved in 3 (10.7%), SD in 18 (64.3%, with DCR of 75%), and PD in 7 (25%). For all 37 patients, median PFS was 3.55 months (95% CI = 2.1- 5.72) and mOS was 5.55 months (95% CI = 4.04 -NA) with survival rate of 42 % at 12 months, and 38% at 18 months. Medan PFS and OS of 30 patients who had ≥1 cycle were 3.91 months (95% CI = 3.55-9.79) and 13.4 months (95% CI = 5.06 - NA), respectively. The overall toxicity profile was as expected, with G3/4 AE’s of 40.5%. The most common toxicities were HTN, hypophosphatemia, hand-foot skin reaction, and increased serum bilirubin. Dose modification was required in 11 (30.6%) patients. Tumor samples were collected in 80% of patients, with planned correlative studies underway. Conclusions: This study showed promising efficacy of regorafenib in chemotherapy refractory advanced/metastatic cholangiocarcinoma. Further studies to confirm the clinic efficacy are recommended. Clinical trial information: NCT02053376.

3054 Background: Microsatellite stable (MSS) metastatic colorectal cancer (mCRC) has relatively poor tumoral infiltration of CD8+ T cells and is resistant to pembrolizumab (Pembro) when compared to MSI-H mCRC. DNA hypomethylating agent induces epigenetic expression of multiple genes including cancer-testis antigens in CRC, which are recognized by cytotoxic CD8+ T cells in vitro and in vivo. This trial tested whether concurrent treatment with azacitidine (Aza) could enhance the anti-tumor activity of Pembro. Methods: This is a phase 2 trial to evaluate anti-tumor activity and safety of Pembro plus Aza in patients (pts) with previously treated mCRC without any further standard chemotherapy option. Pts received Pembro 200 mg IV on day 1 of each cycle Q3W and Aza 100 mg daily SQ injection on days 1-5 of each cycle Q3W. Primary endpoint was response rate (ORR) using RECIST v1.1. Secondary endpoints included progression-free survival (PFS) and overall survival (OS). Tumor tissues were collected for correlative studies. Results: Thirty-one pts were enrolled [median age, 61 years (range, 30-79); 17 M/14 F; ECOG PS 0/1 (58%/42%); 30 pts with MSS mCRC]. Pts received at least 2 lines of prior systemic chemotherapy for mCRC (median, 3; range, 1-5). Thirty pts received at least one dose of study therapy (median, 3 cycles; range, 1-8). Ten pts could not complete the first 3 cycles due to rapid symptomatic tumor progression. One pt with MSS mCRC achieved PR and 3 pts had SD as best response. The ORR was 3% (1/30; 95% CI, 0.1-17%). Seven pts with PD at the end of cycle 3 continued on study therapy, and 2 pts had stabilization of tumor progression. Median PFS was 2.1 months (95% CI, 1.8-2.8), and median OS was 6.2 months (95% CI, 3.5-8.7). While treatment-related adverse events (TRAEs) were reported in 63% of pts, most of the TRAEs were Gr 1/2 (96%). Frequent TRAEs possibly related to Aza were anemia (n = 5), constipation (n = 5), and leukopenia (n = 4); and possibly related to both Aza and Pembro were nausea (n = 5) and fatigue (n = 5). Gr 3 TRAEs included anemia (n = 1), ALT elevation (n = 1), and alkaline phosphatase elevation (n = 1). Conclusions: Pembro plus Aza is feasible with a tolerable safety profile but appears to have minimal anti-tumor effect for MSS mCRC. Clinical trial information: NCT02260440.