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Purpose: Regional nodal irradiation (RNI) for breast cancer yields improvements in disease outcomes, yet comprehensive target coverage often increases cardiac radiation therapy (RT) dose. Volumetric modulated arc therapy (VMAT) may mitigate high-dose cardiac exposure, although it often increases the volume of low-dose exposure. The cardiac implications of this dosimetric configuration (in contrast to historic 3D conformal techniques) remain uncertain. Methods and Materials: Eligible patients receiving adjuvant RNI using VMAT for locoregional breast cancer were prospectively enrolled in an IRB-approved study. Echocardiograms were performed prior to RT, at the conclusion of RT, and 6 months following RT. Echocardiographic parameters were measured by a single reader and measures were compared pre- and post-RT via the signed-rank test. Changes in echocardiographic parameters over time were compared to mean and max heart doses via the Spearman correlation test. Results: Among 19 evaluable patients (median age 38 years), 89% (n = 17) received doxorubicin and 37% (n = 7) received trastuzumab/pertuzumab combination therapy. All patients received VMAT-based whole-breast/chest wall and RNI. The average mean heart dose was 456 cGy (range, 187-697 cGy) and the average max heart dose was 3001 cGy (1560-4793 cGy). Among salient echocardiographic parameters, no significant decrement in cardiac function was observed when comparing pre-RT to 6 months post-RT: mean left ventricular ejection fraction (LVEF) was 61.8% (SD 4.4%) pre-RT and 62.7% (SD 3.8%) 6 months post-RT (P = .493); mean global longitudinal strain (GLS) was –19.3% (SD 2.2%) pre-RT and –19.6% (SD 1.8%) 6 months post-RT (P = .627). No individual patient exhibited reduced LVEF or sustained decrement in GLS. No correlations were observed for changes in LVEF or GLS when compared to mean or maximum heart doses (P > .1 for all). Conclusions: VMAT for left-sided RNI yielded no significant early decrement in echocardiographic parameters of cardiac function, including LVEF and GLS, within this limited cohort. No patient exhibited significant LVEF changes, and none exhibited sustained decrements in GLS. VMAT may be a reasonable approach to cardiac avoidance in patients requiring RNI, including those receiving anthracyclines and HER2-directed therapy. Larger cohorts with longer follow-ups will be needed to validate these findings.

Purpose: Accelerated partial breast irradiation (APBI) after breast-conserving surgery offers a well-tolerated adjuvant radiation therapy option for patients with breast cancer. We sought to describe patient-reported acute toxicity as a function of salient dosimetric parameters during and after an APBI regimen of 40 Gy in 10 once-daily fractions. Methods and Materials: From June 2019 to July 2020, patients undergoing APBI were assigned a weekly, response-adapted, patient reported outcomes-common terminology criteria for adverse events-based acute toxicity assessment. Patients reported acute toxicity during treatment and for up to 8 weeks after treatment. Dosimetric treatment parameters were collected. Descriptive statistics and univariable analyses were used to summarize patient-reported outcomes and their correlation to corresponding dosimetric measures, respectively. Results: Overall, 55 patients who received APBI completed a total of 351 assessments. Median planning target volume was 210 cc (range, 64-580 cc), and median planning target volume:ipsilateral breast volume ratio was 0.17 (range, 0.05-0.44). Overall, 22% of patients reported moderate breast enlargement and 27% reported maximum skin toxicity as severe or very severe. Furthermore, 35% of patients reported fatigue, and 44% of patients reported pain in the radiated area as moderate to very severe. Median time to first report of any moderate to very severe symptom was 10 days (interquartile range, 6-27 days). By 8 weeks after APBI, most patients reported resolution of symptoms, with 16% reporting residual moderate symptoms. Upon univariable analysis, none of the ascertained salient dosimetric parameters were associated with maximum symptoms or with the presence of moderate to very severe toxicity. Conclusions: Weekly assessments during and after APBI showed that patients experienced moderate to very severe toxicities, most commonly skin toxicity, but that these typically resolved by 8 weeks after radiation therapy. More comprehensive evaluations among larger cohorts are warranted to define the precise dosimetric parameters that correspond to outcomes of interest.

Purpose: Radiation therapy (RT) after breast-conserving surgery (BCS) for ductal carcinoma in situ (DCIS) reduces invasive and in situ recurrences. Whereas landmark studies suggest that a tumor bed boost improves local control for invasive breast cancer, the benefit in DCIS remains less certain. We evaluated outcomes of patients with DCIS treated with or without a boost. Methods and Materials: The study cohort comprised patients with DCIS who underwent BCS at our institution from 2004 to 2018. Clinicopathologic features, treatment parameters, and outcomes were ascertained from medical records. Patient and tumor characteristics were evaluated relative to outcomes using univariable and multivariable Cox models. Recurrence-free survival (RFS) estimates were generated using the Kaplan-Meier method. Results: We identified 1675 patients who underwent BCS for DCIS (median age, 56 years; interquartile range, 49-64 years). Boost RT was used in 1146 cases (68%) and hormone therapy in 536 (32%). At a median follow-up of 4.2 years (interquartile range, 1.4-7.0 years), we observed 61 locoregional recurrence events (56 local, 5 regional) and 21 deaths. Univariable logistic regression demonstrated that boost RT was more common among younger patients (P < .001) with positive or close margins (P < .001) and with larger tumors (P < .001) of higher grade (P = .025). The 10-year RFS rate was 88.8% among those receiving a boost and 84.3% among those without a boost (P = .3), and neither univariable nor multivariable analyses revealed an association between boost RT and locoregional recurrence. Conclusions: Among patients with DCIS who underwent BCS, use of a tumor bed boost was not associated with locoregional recurrence or RFS. Despite a preponderance of adverse features among the boost cohort, outcomes were similar to those of patients not receiving a boost, suggesting that a boost may mitigate risk of recurrence among patients with high-risk features. Ongoing studies will elucidate the extent to which a tumor bed boost influences disease control rates.

Purpose: : Guidelines for early-stage breast cancer allow for radiation therapy (RT) omission after breast conserving surgery among older women, though high utilization of RT persists. This study explored surgeon referral and the effect of a productivity-based bonus metric for radiation oncologists in an academic institution with centralized quality assurance review. Methods and materials: : We evaluated patients ≥70 years of age treated with breast conserving surgery for estrogen receptor (ER)+ pT1N0 breast cancer at a single tertiary cancer network between 2015 and 2018. The primary outcomes were radiation oncology referral and RT receipt. Covariables included patient and physician characteristics and treatment decisions before versus after productivity metric implementation. Univariable generalized linear effects models explored associations between these outcomes and covariables. Results: : Of 703 patients included, 483 (69%) were referred to radiation oncology and 273 (39%) received RT (among those referred, 57% received RT). No difference in RT receipt pre- versus post-productivity metric implementation was observed (P = .57). RT receipt was associated with younger patient age (70-74 years; odds ratio [OR], 2.66; 95% confidence interval [CI], 1.54-4.57) and higher grade (grade 3; OR, 7.75; 95% CI, 3.33-18.07). Initial referral was associated with younger age (70-74; OR, 5.64; 95% CI, 3.37-0.45) and higher performance status (Karnofsky performance status ≥90; OR, 5.34; 95% CI, 2.63-10.83). Conclusions: : Nonreferral to radiation oncology accounted for half of RT omission but was based on age and Karnofsky performance status, in accordance with guidelines. Lack of radiation oncologist practice change in response to misaligned financial incentives is reassuring, potentially reflecting incentive design and/or centralized quality assurance review. Multi-institutional studies are needed to confirm these findings.

Purpose: A radiation anatomist was trained and integrated into clinical practice at a multi-site academic center. The primary objective of this quality improvement study was to determine whether a radiation anatomist improves the quality of organ-at-risk (OAR) contours, and secondarily to determine the impact on efficiency in the treatment planning process. Methods and Materials: From March to August 2020, all patients undergoing computed tomography–based radiation planning at 2 clinics at Memorial Sloan Kettering Cancer Center were assigned using an “every other” process to either (1) OAR contouring by a radiation anatomist (intervention) or (2) contouring by the treating physician (standard of care). Blinded dosimetrists reported OAR contour quality using a 3-point scoring system based on a common clinical trial protocol deviation scale (1, acceptable; 2, minor deviation; and 3, major deviation). Physicians reported time spent contouring for all cases. Analyses included the Fisher exact test and multivariable ordinal logistic regression. Results: There were 249 cases with data available for the primary endpoint (66% response rate). The mean OAR quality rating was 1.1 ± 0.4 for the intervention group and 1.4 ± 0.7 for the standard of care group (P < .001), with subset analysis showing a significant difference for gastrointestinal cases (n = 49; P

Purpose: For patients with long bone metastases who undergo orthopedic stabilization surgery followed by radiotherapy (RT), it is unclear what extent of hardware coverage by the radiation field is needed for optimal tumor control. Methods and Materials: Long bone metastases treated with surgical intervention followed by radiation between August 2011 to May 2019 from a single institution were reviewed. Local recurrence, defined as any in-bone recurrence, was identified by chart review. Accompanying demographic and treatment characteristics were recorded. Statistical analysis to evaluate factors associated with tumor recurrence included univariate analysis, multivariate analysis, and propensity score matching. Results: Among 138 patients with 145 long bone metastases undergoing postoperative RT with a median follow-up of 29.5 months, 36 bone metastases experienced a local recurrence. Most patients (92%) were treated with conventional RT and the median delivered dose was 30 Gy (interquarile range, 20-30 Gy). On univariate analysis, whole hardware RT field coverage and higher dose (biologically effective dose 10 ≥39 Gy) were associated with reduced local recurrence (0.44 hazard ratio [HR]; 95% confidence interval [CI], 0.22%-0.86%; P = .017; 0.5 HR; 95% CI, 0.26%-0.96%; P = .038, respectively). Covariates of time from surgery to RT start, histology of primary tumor (categorized as resistant vs sensitive), intramedullary hardware placement, reaming procedure, and margin status did not reach statistical significance. To adjust for confounding effects, we also conducted a propensity score matched analysis which confirmed that whole hardware coverage was statistically associated with a decreased risk of recurrence on the matched dataset (0.24 HR; 95% CI, 0.07%-0.84%; P = .026). Conclusions: In this analysis of mostly patients undergoing conventional radiation, coverage of the whole hardware was associated with reduced local recurrence for patients with long bone metastases, consistent with prior reports. Investigation of approaches to further reduce local recurrence, such as preoperative stereotactic radiation, may be warranted.

Purpose: The 2016 American Society for Radiation Oncology consensus guidelines for the use of accelerated partial-breast irradiation (APBI) define “suitable,” “cautionary,” and “unsuitable” populations for this adjuvant breast radiation therapy technique. We sought to determine whether patients in the cautionary group exhibited adverse outcomes after APBI compared with their suitable counterparts. Methods and Materials: We identified 252 consecutively treated patients from a single institution with in situ or early-stage invasive breast cancer who underwent APBI between 2008 and 2017. Treatment technique was uniform throughout the population, consisting of 3-dimensional conformal radiation therapy to 40 Gy administered in 10 daily fractions. Results: One hundred seventy-eight patients (70%) were classified as suitable, 69 (27%) as cautionary, and 5 (2.0%) as unsuitable. Because unsuitable patients were few and had no recurrences, they were excluded from analysis. At a median follow-up time of 3.9 years, 97.2% of patients were free of recurrence. Four patients (1.5% overall; 3 suitable and 1 cautionary) experienced ipsilateral in-breast recurrences, and 1 cautionary patient developed an ipsilateral regional recurrence in an axillary lymph node. There was no significant difference in the rate of ipsilateral breast recurrence (2.4% vs 1.0%) between cautionary and suitable groups. Conclusions: Local recurrences are rare among guideline-defined cautionary patients with in situ or invasive breast cancer treated with APBI delivered via daily 3-dimensional conformal radiation therapy to 40 Gy. At a median follow-up of 3.9 years, no significant differences in local control were noted between cautionary and suitable patient groups. Further study is needed to characterize long-term disease outcomes among various risk groups.

Purpose: Internal mammary node recurrence after definitive breast cancer treatment is poorly characterized, with limited data to guide clinical management. The aim of this study was to analyze the outcomes of patients with recurrent breast cancer involving internal mammary nodes to understand their natural history and determine prognostic factors associated with improved overall survival. Methods and Materials: We performed a retrospective analysis of 553 patients with recurrent breast cancer and identified 161 patients with radiographic evidence of locoregional recurrence as a first event. A total of 67 patients (42%) were identified with internal mammary involvement. Median follow-up times were 76 months from date of initial diagnosis and 30 months from date of recurrence. Results: Of the 67 patients identified with internal mammary node failures, 10 (15%) presented with isolated recurrence, 14 (21%) presented with other sites of locoregional disease, and 43 (64%) presented with concomitant distant metastases. Median overall survival was 2.5 years and significantly associated with extent of disease (P

Purpose: Our goal was to determine the impact of pathologic response after neoadjuvant chemotherapy in triple negative breast cancer (TNBC) on the subsequent risk of locoregional recurrence (LRR) and disease-free survival (DFS) in the setting of adjuvant radiation therapy. Methods and materials: This was an institutional review board–approved retrospective chart review of patients with clinical stage I-III breast cancer treated with neoadjuvant chemotherapy, local surgery (breast conservation or mastectomy), and adjuvant radiation therapy between 1997 and 2015. Medical records were reviewed for clinical stage, tumor grade and subtype, neoadjuvant chemotherapy regimen, type of surgery, pathologic stage, use of radiation therapy, date and location of recurrence, and date of death. Molecular subtypes were defined using immunohistochemistry and histologic grade. ypT0 and ypN0 were defined as no residual invasive disease in breast or nodes, respectively. LRR was defined as any failure within the breast, chest wall, or regional lymph nodes. Statistical analysis was performed; LRR and DFS rates over 30 months were determined from Kaplan-Meier plots. Results: Ninety-four patients with TNBC were analyzed, of whom 72 received radiation therapy. This subgroup was isolated for further investigation. Median follow-up was 32.5 months in this group. The pathologic complete response (pCR) rate was 36%, and presence or absence of disease in breast and/or nodes was significantly predictive of LRR. In TNBC patients who received radiation therapy, 30-month LRR was 22% in 41 patients with ypT+ versus 0% in 31 patients with ypT0 (P = .003), 23% in 31 patients with ypN+ versus 5% in 41 patients with ypN0 (P = .016), and 20% in 46 patients with residual disease in breast or nodes versus 0% in 26 patients with pCR (P = .015). The difference in the rate of LRR between those who underwent lumpectomy versus mastectomy did not reach significance (8% vs 17%, respectively). Furthermore, patients with residual disease had a higher rate of DFS events (hazard ratio, 3.58; 95% confidence interval, 1.37-9.41; P = .006). The difference in DFS was not significantly associated with the type of surgery received. Conclusions: Patients with TNBC treated with neoadjuvant chemotherapy who have residual disease in the breast or lymph nodes at the time of surgery have significantly higher rates of locoregional failure and lower DFS compared with those with a pCR despite the use of adjuvant radiation therapy. Strategies to intensify therapy for patients with residual disease warrant further investigation.