Navigating Breast Cancer Oligometastasis and Oligoprogression: Current Landscape and Future Directions

PURPOSE

We examine the potential for curative approaches among metastatic breast cancer (MBC) patients by exploring the recent literature on local ablative therapies like surgery and stereotactic body radiation therapy (SBRT) in patients with oligometastatic (OM) breast cancer. We also cover therapies for MBC patients with oligoprogressive (OP) disease.

KEY FINDINGS

Surgery and SBRT have been studied for OM and OP breast cancer, mainly in retrospective or non-randomized trials. While many studies demonstrated favorable results, a cooperative study and single-institution trial found no support for surgery/SBRT in OM and OP cases, respectively.

CONCLUSION

While there is interest in applying local therapies to OM and OP breast cancer, the current randomized data does not back the routine use of surgery or SBRT, particularly when considering the potential for treatment-related toxicities. Future research should refine patient selection through advanced imaging and possibly explore these therapies specifically in patients with hormone receptor-positive or HER2-positive disease.

Partial Breast Irradiation for Patients With Early-Stage Invasive Breast Cancer or Ductal Carcinoma In Situ: An ASTRO Clinical Practice Guideline

PURPOSE

This guideline provides evidence-based recommendations on appropriate indications and techniques for partial breast irradiation (PBI) for patients with early-stage invasive breast cancer and ductal carcinoma in situ.

METHODS

ASTRO convened a task force to address 4 key questions focused on the appropriate indications and techniques for PBI as an alternative to whole breast irradiation (WBI) to result in similar rates of ipsilateral breast recurrence (IBR) and toxicity outcomes. Also addressed were aspects related to the technical delivery of PBI, including dose-fractionation regimens, target volumes, and treatment parameters for different PBI techniques. The guideline is based on a systematic review provided by the Agency for Healthcare Research and Quality. Recommendations were created using a predefined consensus-building methodology and system for grading evidence quality and recommendation strength.

RESULTS

PBI delivered using 3-dimensional conformal radiation therapy, intensity modulated radiation therapy, multicatheter brachytherapy, and single-entry brachytherapy results in similar IBR as WBI with long-term follow-up. Some patient characteristics and tumor features were underrepresented in the randomized controlled trials, making it difficult to fully define IBR risks for patients with these features. Appropriate dose-fractionation regimens, target volume delineation, and treatment planning parameters for delivery of PBI are outlined. Intraoperative radiation therapy alone is associated with a higher IBR rate compared with WBI. A daily or every-other-day external beam PBI regimen is preferred over twice-daily regimens due to late toxicity concerns.

CONCLUSIONS

Based on published data, the ASTRO task force has proposed recommendations to inform best clinical practices on the use of PBI.

Incident Atrial Fibrillation and Survival Outcomes in Esophageal Cancer following Radiotherapy

PURPOSE

Radiation therapy (RT) associates with long-term cardiotoxicity. In preclinical models, RT exposure induces early cardiotoxic arrhythmias including atrial fibrillation (AF). Yet, whether this occurs in patients is unknown.

METHODS AND MATERIALS

Leveraging a large cohort of consecutive patients with esophageal cancer treated with thoracic RT from 2007 to 2019, we assessed incidence and outcomes of incident AF. Secondary outcomes included major adverse cardiovascular events (MACE), defined as AF, heart failure, ventricular arrhythmias, and sudden death, by cardiac RT dose. We also assessed the relationship between AF development and progression-free and overall survival. Observed incident AF rates were compared with Framingham predicted rates, and absolute excess risks were estimated. Multivariate regression was used to define the relationship between clinical and RT measures, and outcomes. Differences in outcomes, by AF status, were also evaluated via 30-day landmark analysis. Furthermore, we assessed the effect of cardiac substructure RT dose (eg, left atrium, LA) on the risk of post RT-related outcomes.

RESULTS

Overall, from 238 RT treated patients with esophageal cancer, 21.4% developed incident AF, and 33% developed MACE with the majority (84%) of events occurring ≤2 years of RT initiation (median time to AF, 4.1 months). Cumulative incidence of AF and MACE at 1 year was 19.5%, and 25.7%, respectively; translating into an observed incident AF rate of 824 per 10,000 person-years, compared with the Framingham predicted rate of 92 (relative risk, 8.96; P < .001, absolute excess risk 732). Increasing LA dose strongly associated with incident AF (P = .001); and those with AF saw worse disease progression (hazard ratio, 1.54; P = .03). In multivariate models, outside of traditional cancer-related factors, increasing RT dose to the LA remained associated with worse overall survival.

CONCLUSIONS

Among patients with esophageal cancer, radiation therapy increases AF risk, and associates with worse long-term outcomes.

Racial Disparities in Breast Cancer: from Detection to Treatment

PURPOSE OF REVIEW

Update on current racial disparities in the detection and treatment of breast cancer.

RECENT FINDINGS

Breast cancer remains the leading cause of cancer death among Black and Hispanic women. Mammography rates among Black and Hispanic women have surpassed those among White women, with studies now advocating for earlier initiation of breast cancer screening in Black women. Black, Hispanic, Asian, and American Indian and Alaskan Native women continue to experience delays in diagnosis and time to treatment. Further, racial discrepancies in receipt of guideline-concordant care, access to genetic testing and surgical reconstruction persist. Disparities in the initiation, completion, toxicity, and efficacy of chemotherapy, endocrine therapy, and targeted drug therapy remain for racially marginalized women. Efforts to evaluate the impact of race and ethnicity across the breast cancer spectrum are increasing, but knowledge gaps remain and further research is necessary to reduce the disparity gap.

Stereotactic Radiosurgery for Women Older than 65 with Breast Cancer Brain Metastases

BACKGROUND

Breast cancer is the second most common cause of brain metastases (BM). Despite increasing incidence of BM in older women, there are limited data on the optimal management of BM in this age group. In this study, we assessed the survival outcomes and treatment patterns of older breast cancer patients ≥65 years old with BM compared to younger patients at our institution.

METHODS

An IRB-approved single-institutional retrospective review of biopsy-proven breast cancer patients with BM treated with 1- to 5-fraction stereotactic radiation therapy (SRS) from 2015 to 2020 was performed. Primary endpoint was intracranial progression-free survival (PFS) defined as the time interval between the end of SRS to the date of the first CNS progression. Secondary endpoints were overall survival (OS) from the end of SRS and radiation treatment patterns. Kaplan-Meier estimates and Cox proportional hazard regression method were used for survival analyses.

RESULTS

A total of 112 metastatic breast cancer patients with BMs were included of which 24 were ≥65 years old and 88 were <65 years old. Median age at RT was 72 years (range 65-84) compared to 52 years (31-64) in younger patients. There were significantly higher number of older women with ER/PR positive disease (75% vs. 49%, p = 0.036), while younger patients were more frequently triple negative (32% vs. 12%, p = 0.074) and HER2 positive (42% vs. 29%, p = 0.3). Treatment-related adverse events were similar in both groups. Overall, 14.3% patients had any grade radiation necrosis (RN) (older vs. young: 8.3% vs. 16%, p = 0.5) while 5.4% had grade 3 or higher RN (0% vs. 6.8%, p = 0.7). Median OS after RT was poorer in older patients compared to younger patients (9.5 months vs. 14.5 months, p = 0.037), while intracranial PFS from RT was similar between the two groups (9.7 months vs. 7.1 months, p = 0.580). On univariate analysis, significant predictors of OS were age ≥65 years old (hazard risk, HR = 1.70, p = 0.048), KPS ≤ 80 (HR = 2.24, p < 0.001), HER2 positive disease (HR = 0.46, p < 0.001), isolated CNS metastatic disease (HR = 0.29, p < 0.001), number of brain metastases treated with RT (HR = 1.06, p = 0.028), and fractionated SRS (HR = 0.53, p = 0.013). On multivariable analysis, KPS ≤ 80, HER2 negativity and higher number of brain metastases predicted for poorer survival, while age was not a significant factor for OS after adjusting for other variables. Patients who received systemic therapy after SRS had a significantly improved OS on univariate and multivariable analysis (HR = 0.32, p < 0.001). Number of brain metastases treated was the only factor predictive of worse PFS (HR = 1.06, p = 0.041), which implies a 6% additive risk of progression for every additional metastasis treated.

CONCLUSIONS

Although older women had poorer OS than younger women, OS was similar after adjusting for KPS, extracranial progression, and systemic therapy; and there was no difference in rates of intracranial PFS, neurological deaths, and LMD in the different age groups. This study suggests that age alone may not play an independent role in treatment-selection and that outcomes for breast cancer patients with BMs and personalized decision-making including other clinical factors should be considered. Future studies are warranted to assess neurocognitive outcomes and other radiation treatment toxicities in older patients.

Patient-driven decisions and perceptions of the 'safest possible choice': insights from patient-provider conversations about how some breast cancer patients choose contralateral prophylactic mastectomy

OBJECTIVE

Observe patient-clinician communication to gain insight about the reasons underlying the choice of patients with unilateral breast cancer to undergo contralateral prophylactic mastectomy (CPM), despite lack of survival benefit, risk of harms, and cautions expressed by surgical guidelines and clinicians.

METHODS & MEASURES

WORDS is a prospective study that explored patient-clinician communication and patient decision making. Participants recorded clinical visits through a downloadable mobile application. We analyzed 44 recordings from 22 patients: 9 who chose CPM, 8 who considered CPM but decided against it, and 5 who never considered CPM. We used abductive analysis combined with constructivist grounded theory methods.

RESULTS

Decisions to undergo CPM are patient-driven and motivated by perceptions that CPM is the most aggressive, and therefore safest, treatment option available. These decisions are shaped not primarily by the content of conversations with clinicians, but by the history of cancer in patients' families, their own first-hand experiences with cancers among loved ones, fear for their children, and anxiety about cancer recurrence.

CONCLUSION

The perception that CPM is the safest, most aggressive option strongly influences patients, despite scientific evidence to the contrary. Future efforts to address high CPM rates should focus on patient-driven decision making and cancer-related fears.

Moving the Needle Forward in Genomically-Guided Precision Radiation Treatment

Radiation treatment (RT) is a mainstay treatment for many types of cancer. Recommendations for RT and the radiation plan are individualized to each patient, taking into consideration the patient's tumor pathology, staging, anatomy, and other clinical characteristics. Information on germline mutations and somatic tumor mutations is at present rarely used to guide specific clinical decisions in RT. Many genes, such as ATM, and BRCA1/2, have been identified in the laboratory to confer radiation sensitivity. However, our understanding of the clinical significance of mutations in these genes remains limited and, as individual mutations in such genes can be rare, their impact on tumor response and toxicity remains unclear. Current guidelines, including those from the National Comprehensive Cancer Network (NCCN), provide limited guidance on how genetic results should be integrated into RT recommendations. With an increasing understanding of the molecular underpinning of radiation response, genomically-guided RT can inform decisions surrounding RT dose, volume, concurrent therapies, and even omission to further improve oncologic outcomes and reduce risks of toxicities. Here, we review existing evidence from laboratory, pre-clinical, and clinical studies with regard to how genetic alterations may affect radiosensitivity. We also summarize recent data from clinical trials and explore potential future directions to utilize genetic data to support clinical decision-making in developing a pathway toward personalized RT.

Outcomes of Moderately Dose Escalated Hypofractionated Chemoradiation for Pancreatic Cancer

PURPOSE/OBJECTIVE(S)

A modestly hypofractionated course of chemoradiation (CRT) consisting of 36 Gy/15 fractions (F) concurrent with gemcitabine used in PREOPANC and phase II trials has become increasingly common for the treatment of borderline resectable (BR) and locally advanced (LA) pancreatic cancer (PC). Achieving an R0 resection remains a key prognostic factor in PC. We tested whether escalating dose beyond standard dosing (SD) of 36-39 Gy/15 F (or 50-54 Gy/25-30 F) would improve R0 resection rates and outcomes while respecting nearby organs at risk.

MATERIALS/METHODS

This was a retrospective analysis of consecutive patients at our institution from 2012-2022 with BR/LA PC treated with moderate dose escalated (MDE) (45 Gy/15 F, N = 45) or SD (36-39 Gy/15 F, N = 68 or 50-54 Gy/25-30 F, N = 25) CRT. For MDE, a 5 mm expansion from the duodenum, small bowel, and stomach was created (GI_PRV); PTV was cropped from this structure and prescribed 45 Gy/15 F. The primary endpoint was R0 resection rate with secondary endpoints of cumulative incidence of local progression (LP, recurrence after surgery/imaging progression if no surgery) with death as a competing risk (LP after occurrence of distant metastasis [DM] were still captured), cumulative incidence of DM, and overall survival (OS). Univariable and multivariable competing risks regression analyses were performed to determine the association between baseline covariates and LP.

RESULTS

We identified 45 patients treated with MDE and 93 treated with SD. Most patients presented with BR disease (55.6% MDE; 54.8% SD) and received neoadjuvant chemotherapy with FOLFIRINOX (98% MDE; 99% SD). All patients in the MDE group and 99% in the SD group received concurrent chemotherapy with gemcitabine used most often (96% MDE; 77% SD). Median follow-up was 17 m (IQR 13-27 m). Surgical resection rates were similar between groups (33.3% MDE vs. 39.8% SD, p = 0.46). Amongst patients that had surgery, R0 resection rates were non-significantly higher in the MDE group (73.3% vs. 47.4%, p = 0.09). Cumulative incidence of LP at 18 m was significantly lower in the MDE group (9.0% vs. 24.8%, p = 0.04). No difference in rates of DM (51.2% MDE vs. 59.6% SD, p = 0.92) or OS at 18 m (53.9% vs. 53.6%, p = 0.89) were observed. On multivariable analysis, MDE (HR = 0.39, p = 0.03) and pancreatic head location (HR = 0.51, p = 0.04) were the only factors independently associated with LP. Rates of grade 2+ gastrointestinal toxicity during CRT (20% MDE vs. 20.9% SD, p = 0.91) and ≤90 days of completing CRT (11.6% MDE vs. 14.8%, p = 0.62) were similar between groups, as were rates of grade 3+ hematologic toxicity (52.3% MDE vs. 41.3% SD, p = 0.23).

CONCLUSION

In this single institutional study, we found MDE is a simple, safe, and effective strategy associated with improved local control, higher R0 resection rates, and similar toxicity to SD CRT for patients with BR/LA PC. Further prospective data is needed to clarify the role of dose-escalated RT in the management of this lethal malignancy.

Implementation of a Breast Intraoperative Oncoplastic Form to Aid Management of Oncoplastic Surgery

INTRODUCTION

Oncoplastic breast conservation surgery (BCS) uses concurrent reduction and/or mastopexy with lumpectomy to improve aesthetic outcomes. However, tissue rearrangement can shift the original tumor location site in relation to external breast landmarks, resulting in difficulties during re-excision for a positive margin and accurate radiation targeting. We developed the Breast Intraoperative Oncoplastic (BIO) form to help depict the location of the tumor and breast reduction specimen. This study seeks to assess physician perspectives of the implementation outcomes.

METHODS

From February 2021 to April 2021, the BIO form was used in 11 oncoplastic BCS cases at a single institution. With institutional review board approval, surgical oncologists (SOs), plastic surgeons (PSs), and radiation oncologists (ROs) were administered a 12-question validated survey on Acceptability of Intervention Measure (AIM), Intervention Appropriateness Measure (IAM), and Feasibility of Intervention Measure (FIM), using a 5-point Likert scale during initial implementation and at 6-month reassessment.

RESULTS

Twelve physicians completed the survey initially (4 SOs, 4 PSs, and 4 ROs). The mean scores for Acceptability of Intervention Measure, Intervention Appropriateness Measure, and Feasibility of Intervention Measure were high (4.44, 4.56, and 4.56, respectively). Twelve completed the second survey (5 SOs, 3 PSs, and 4 ROs). The mean scores were marginally lower (4.06, 4.21, and 4.25). There were no significant differences when stratified by number of years in practice or specialty. Free text comments showed that 75% of physicians found the form helpful in oncoplastic BCS.

CONCLUSIONS

The data indicate high feasibility, acceptability, and appropriateness of the BIO form. Results of this study suggest multidisciplinary benefits of implementing the BIO form in oncoplastic BCS.

Are All Prognostic Stage IB Breast Cancers Equivalent?

PURPOSE/OBJECTIVE(S)

The 8th edition of the American Joint Committee on Cancer (AJCC) has recognized the prognostic influence of histologic grade and biomarker status for breast cancer (BC). Contemporary BC staging includes both anatomic tumor extent and prognostic stage. However, prognostic stage IB remains heterogeneous and includes patients with locally advanced anatomic pathologic stage IIIA-B (pT3N1 or pT1-3N2, G1-2) hormone-receptor positive/HER2-negative BC (LA-HR+/HER2-) as well as patients with early-stage anatomic clinical/pathologic stage IA (T1cN0, G2-3) triple-negative BC (ES-TNBC). We hypothesized that although both are classified as prognostic stage IB BC, overall survival (OS) is worse for LA-HR+/HER2- compared to ES-TNBC.

MATERIALS/METHODS

We used the National Cancer Database to identify patients with surgically-resected LA-HR+/HER2- BC (pT3N1 or pT1-3N2, grade 1-2) and those with ES-TNBC (T1N0, grade 2-3) from 2004-2017. Patients were excluded if receptor status, tumor grade, and/or TNM staging data were unknown. HR+/HER2- patients treated with neoadjuvant therapy were also excluded. The primary endpoint was OS. Multivariable Cox regression analysis was used to evaluate differences in OS between LA-HR+/HER2- BC and ES-TNBC (adjusting for baseline patient demographic characteristics) in the entire cohort and in the subset of patients that received appropriate treatment based on anatomic stage: radiation (RT), chemotherapy (CT) and hormone therapy for LA-HR+/HER2- BC and CT or CT+RT for ES-TNBC treated with mastectomy or lumpectomy, respectively. We report hazard ratios (HR) with 95% confidence intervals (CI) with p<0.05 considered statistically significant.

RESULTS

A total of 45,818 patients met inclusion criteria (N = 17,359 with LA-HR+/HER2- BC and N = 28,459 with ES-TNBC). Over 75% of the LA-HR+/HER2- BC patients have anatomic pathologic stage IIIB disease (pT1-3N2, G1-2). With a median follow-up of 56 months, the 6-year OS rates were 86.1% (LA-HR+/HER2-) vs. 90.4%patients (ES-TNBC) which corresponded to a 63% relative increased risk of death in LA-HR+/HER2- patients compared to ES-TNBC patients (HR = 1.63, 95% CI 1.53-1.73, p<0.0001) after adjusting for all covariates. Approximately 66% (N = 11,533) LA-HR+/HER2- and 69% (N = 19,512) ES-TNBC received appropriate therapy. The 6-year OS was 91.8% (LA-HR+/HER2-) vs. 93.3% (ES-TNBC) which corresponded to a 35% increased risk of death in the LA-HR+/HER2- patients compared to ES-TNBC (adjusted HR = 1.35, 95% 1.24-1.48, p<0.0001). Other covariates associated with OS were age, income, insurance status, facility type, and ethnicity/race.

CONCLUSION

We found that LA-HR+/HER2- BC has significantly worse OS compared to ES-TNBC despite both being classified as prognostic stage IB, even when accounting for treatments delivered. The categorization of pT3N1 or pT1-3N2, G1-2 HR+/HER2- BC as prognostic stage IB needs to be reconsidered in order to provide patients with more accurate information regarding expected OS.

Omission of Adjuvant Radiotherapy in Low-Risk Elderly Males with Breast Cancer

PURPOSE/OBJECTIVE(S)

Randomized clinical trials demonstrate that lumpectomy + hormone therapy (HT) without radiation therapy (RT) yields equivalent survival and acceptable local-regional outcomes in elderly women with early-stage, node-negative (T1-2N0) hormone-receptor positive (HR+) breast cancer. Whether these data apply to men with the same inclusion criteria remains unknown. We hypothesized that outcomes in males would be comparable to those seen in females, with RT not conferring an overall survival (OS) benefit over HT alone.

MATERIALS/METHODS

We conducted a retrospective matched-cohort study using the National Cancer Database for males ≥65 years with pathologic T1-2N0 (≤3 cm) HR+ breast cancer treated with breast conserving surgery with negative margins from 2004-2019. Patients who received chemotherapy, had nodal or distant metastases, or unknown follow-up were excluded. Adjuvant treatment was classified as HT alone, RT alone, or HT+RT. Due to limitations of survival analysis on retrospective data, male patients were matched with female patients to determine comparable outcomes based on age (± 3 years), Charlson Deyo comorbidity score, T-stage, and adjuvant treatment. Survival analysis was performed using Cox regression and Kaplan-Meier analysis. To adjust for confounding, inverse probability of treatment weighting (IPTW) was used.

RESULTS

A total of 523 patients met inclusion criteria, with 24.4% receiving HT, 16.3% receiving RT, and 59.2% receiving HT+RT. Median follow-up was 6.9 years (IQR: 5.0-9.4 years). Unadjusted 5-yr OS rates in the HT, RT, and HT+RT cohorts were 79.2% (95% CI 70.7-85.5%), 80.9% (95% CI 70.3-88.0%), and 93.3% (95% CI 89.7-95.7%), respectively. Adjusted 10-yr OS rates in the HT, RT, and HT+RT cohorts were 82.3% (95% CI 78.6-85.5%), 83.6% (95% CI 80.0-86.7%), and 92.8% (95% CI 90.1-94.8%), respectively. On unadjusted multivariable Cox regression analysis (MVA), relative to HT, receipt of HT+RT was associated with improvements in OS (HR: 0.603; 95% CI: 0.410-0.888; p = 0.01). RT alone was not associated with improved OS (HR: 1.116; 95% CI: 0.710-1.755; p = 0.633). On adjusted MVA, relative to HT, receipt of HT+RT was associated with improvements in OS (HR: 0.551; 95% CI: 0.370-0.820; p = 0.003). Again, RT alone was not associated with improved OS (HR: 0.991; 95% CI: 0.613-1.604; p = 0.972). Other factors associated with OS included age, Charlson Deyo score, T stage, and grade. Overall, in the matched women, the same trends were found as in the men, the best survival was in HT+RT, but no difference in OS between HT vs. RT.

CONCLUSION

Among men ≥65 years old with T1-2N0 HR+ breast cancer, RT alone did not confer an OS benefit over HT alone. Combined RT+HT did yield improvements in OS, though there are likely significant unmeasured confounders contributing to these outcomes in patients treated with the most aggressive approach. Our findings support that RT omission may be a reasonable option in elderly men with T1-2N0 HR+ breast cancer treated with lumpectomy + HT.

The Axillary Lateral Vessel Thoracic Junction Is Not an Organ at Risk for Breast Cancer-Related Lymphedema

PURPOSE

Breast cancer-related lymphedema (BCRL) is a treatment complication that significantly reduces patient quality of life. Regional nodal irradiation (RNI) may increase the risk of BCRL. Recently, a region of the axilla known as the axillary-lateral thoracic vessel juncture (ALTJ) was identified as a potential organ at risk (OAR). Here, we set out to validate whether radiation dose to the ALTJ is associated with BCRL.

METHODS AND MATERIALS

We identified patients with stage II-III breast cancer treated with adjuvant RNI from 2013 to 2018, excluding those with BCRL preradiation. We defined BCRL as difference in arm circumference between the ipsilateral and contralateral limb >2.5 cm at any 1 encounter or ≥2 cm on ≥2 visits. All patients suspected of having BCRL at routine follow-up visits were referred to physical therapy for confirmation. The ALTJ was retrospectively contoured and dose metrics were collected. Cox proportional hazards regression models were used to test the association between clinical and dosimetric parameters with the development of BCRL.

RESULTS

The study population included 378 patients with a median age of 53 years, median body mass index of 28.4 kg/m2, and median of 18 axillary nodes removed; 71% underwent mastectomy. Median follow-up was 70 months (interquartile range, 55-89.7 months). BCRL developed in 101 patients at a median of 18.9 months (interquartile range, 9.9-32.4 months), with a corresponding 5-year cumulative incidence BCRL of 25.8%. On multivariate analysis, none of the ALTJ metrics were associated with BCRL risk. Only increasing age, increasing body mass index, and increasing number of nodes were associated with a higher risk of developing BCRL. The 6-year locoregional recurrence rate was 3.2%, the axillary recurrence rate was 1.7%, and the isolated axillary recurrence rate was 0%.

CONCLUSIONS

The ALTJ is not validated as a critical OAR for reducing BCRL risk. Until such an OAR is discovered, the axillary PTV should not be modified or dose reduced in efforts to reduce BCRL.

Treatment Patterns and Outcomes for Patients with Ampullary Carcinoma Who Do Not Undergo Surgery

Surgical resection is the standard of care for ampullary adenocarcinoma (AC). Many patients are ineligible due to comorbidities/advanced disease. Evidence for the optimal non-operative management of localized AC is lacking. We hypothesize that patients treated with chemotherapy (CT) and definitive radiation (DRT) will have superior survival (OS) compared to those treated with CT alone. We performed a retrospective review of the National Cancer Database from 2004 to 2017 to identify patients with non-metastatic AC and no surgical intervention. Patients were categorized as having received no treatment, palliative radiotherapy (PRT) alone, CT alone, CT + PRT, DRT alone, or CT + DRT. We utilized Kaplan-Meier analysis to determine OS and the log-rank test to compare survival curves. Among 2176 patients, treatment groups were: No treatment (71.2%), PRT alone (1.9%), CT alone (13.1%), CT + PRT (1.6%), DRT alone (2.4%), and CT + DRT (9.7%). One-year OS varied by treatment group, ranging from 35.1% (PRT alone) to 59.4% (CT + DRT). The one-year OS in a matched cohort was not significantly different between CT alone and CT + DRT (HR 0.87, 95% CI 0.69-1.10, p = 0.87). Most patients with non-metastatic AC not treated with surgery do not receive any treatment. There is no difference in one-year OS between those undergoing CT alone and CT + DRT.

Advances in Radiotherapy for Breast Cancer

Breast cancer is the most prevalent cancer in women, and the second leading cause of cancer death in women in the United States. Radiation therapy is an important component in the multimodal management of breast cancer, including early stage and locally advanced breast cancers, as well as metastatic cases. Breast cancer radiation therapy has seen significant advancements over the past 20 years. This article discusses the latest advances in the radiotherapeutic management of breast cancer, especially focusing on the technological advances in radiation treatment planning and techniques that have exploited the understanding of radiation biology.

Not Too Little, Not Too Much: Optimizing More Versus Less Locoregional Treatment for Older Patients With Breast Cancer

Although undertreatment of older women with aggressive breast cancers has been a concern for years, there is increasing recognition that some older women are overtreated, receiving therapies unlikely to improve survival or reduce morbidity. De-escalation of surgery may include breast-conserving surgery over mastectomy for appropriate candidates and omitting or reducing extent of axillary surgery. Appropriate patients to de-escalate surgery are those with early-stage breast cancer, favorable tumor characteristics, are clinically node-negative, and who may have other major health issues. De-escalation of radiation includes reducing treatment course length through hypofractionation and ultrahypofractionation regimens, reducing treatment volumes through partial breast irradiation, omission of radiation for select patients, and reducing radiation dose to normal tissues. Shared decision making, which aims to facilitate patients making decisions concordant with their values, can guide health care providers and patients through complicated decisions optimizing breast cancer care.

Abstract P4-02-17: Impact of low hormone receptor expression on neoadjuvant chemotherapy response and patterns of care in early-stage HER2-negative breast cancer: a US National Cancer Database analysis

Background: Hormone receptor (HR) low (1-10%) HER2-negative breast cancer (BC) is emerging as a distinct subtype with similarities in clinical outcomes to triple-negative BC. However, there is a lack of consensus on treatment recommendations for chemo-immunotherapy and endocrine therapy in this subset. Here, we present results from a US National Cancer Database (NCDB) analyses of patients with HER2-negative BC evaluating response to neoadjuvant chemotherapy (NAC) and patterns of care by HR expression.

Methods: Patients with stage I-III HER2-negative BC diagnosed in 2018 were identified in NCDB, a nationwide oncology outcomes database in the US. Quantitative HR expression was unavailable prior to 2018. Data were categorized into four groups by estrogen receptor (ER) and progesterone receptor (PR) expression: ER&lt; 1% & PR&lt; 1% (HR-Neg), ER 1-10% and/or PR 1-10% (HR-Low), ER &gt;11-30% and/or PR&gt;11-30% (HR-Int), ER&gt; 30% and/or PR &gt; 30% (HR-High). Those with undocumented HR status (3%) or without curative intent surgery (5%) were excluded. The primary outcome was pathologic complete response (pCR) by HR expression in those undergoing neoadjuvant chemotherapy. Key secondary objectives included assessment of clinicopathologic characteristics and practice patterns. The categorical variables were compared between the four groups using a Chi-square test. Age was compared using a Kruskal-Wallis test.

Results: Out of 104,205 incident cases, 2541 (2.4%) were HR-Low and 1241 (1.2%) were HR-Int. Significant differences were found between HR groups with higher grade, clinical stage, and Ki-67 in HR-Low vs. HR-Int or HR-High groups (Table 1). Patients with HR-Low and HR-Int BC were more likely to receive chemotherapy than HR-High (74%, 70% vs. 20%; p &lt; 0.001) and the use of adjuvant endocrine therapy correlated with HR expression. Only half of patients in the HR-Low group received any endocrine therapy compared to higher rates in the HR-Int and HR-High groups (52% vs. 74%, 92%; p&lt; 0.001). pCR rates in those receiving neoadjuvant chemotherapy were significantly different by HR status, with higher pCR rates in HR-Low vs. HR-High groups (p&lt; 0.001) (Table 2). NAC utilization significantly differed between groups. A higher proportion of patients with HR-Low BC received NAC than other HR-positive groups (p &lt; 0.001). Additionally, there was an increased use of NAC in patients with HR-Low BC treated at academic vs. community cancer centers (p&lt; 0.001).

Conclusions: This is one of the largest real-world analyses comparing key differences in biology and practice patterns of HR-Low, HER2-negative BC. Consistent with prior studies, we report HR-Low BC to be a rare and distinct subtype with higher pCR rates compared to HR-High BC. Practice patterns show wide variability in utilization of neoadjuvant chemotherapy and endocrine therapy for these patients. Future studies should address this disparity and enhance representation of patients with HR-Low BC in clinical trials to improve long-term outcomes.

Table 1: Patient demographics

Table 2: Neoadjuvant chemotherapy response amongst differing HR expression levels

Citation Format: Dionisia Quiroga, Michael Grimm, Julie Stephens, Kai Johnson, Nicole Williams, Preeti K. Sudheendra, Mathew A. Cherian, Daniel Stover, Ashley C. Pariser, Margaret Gatti-Mays, Robert Wesolowski, Jose G. Bazan, Sasha Beyer, Ko Un Park, Bridget Oppong, Bhuvaneswari Ramaswamy, Julia White, Sachin R. Jhawar, Sagar Sardesai. Impact of low hormone receptor expression on neoadjuvant chemotherapy response and patterns of care in early-stage HER2-negative breast cancer: a US National Cancer Database analysis [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P4-02-17.

Abstract P3-05-60: Understanding Ethnoracial Differences in Oncotype DX Recurrence Scores in Patients with Early-Stage Breast Cancer: An Analysis Based on Hispanic Ethnicity

Background: Recent studies suggest racial and ethnic differences in tumor genomics and receipt of systemic treatment may be drivers of racial and ethnic disparities in clinical outcomes (e.g., mortality, recurrence) in patients with breast cancer (BC). For patients of Hispanic ethnicity, the relationship between ethnoracial categories (i.e., Hispanic Black, Hispanic White), tumor genomics, and receipt of systemic has not been well elucidated. The objective of this study is to examine implications of ethnoracial categories on Oncotype DX recurrence score (RS), receipt of chemotherapy for high risk RS and endocrine therapy (ET) use in the National Cancer Database (NCDB). Materials/Methods: Patients diagnosed from 2004-2017 with stage I or stage II HR+/HER2- BC with RS available in the NCDB were identified. The data was divided into Black and White patients then stratified by ethnicity. Study ethnoracial categories included non-Hispanic White (NHW), Hispanic White (HW), non-Hispanic Black (NHB) and Hispanic Black (HB). High-risk RS was defined using the original definition of RS&gt;30. On univariable analysis, intra-racial differences in RS score (t-test) and the proportion of patients with high-risk RS (chi-square test) were examined by ethnicity. Systemic therapy (chemotherapy and ET) were assessed with univariable analysis within racial groups by ethnicity (chi-square test). Results: The ethnoracial composition of the cohort was 220,490 (87.5%) NHW, 20,690 (8.2%) HB, 10,477(4.2%) HW and 296 (&lt; 1%) HB. Overall, Hispanic patients had higher mean RS relative to non-Hispanic patients (18.4 [11.8] vs. 18.0 [10.8], p=0.0004) and a higher proportion of RS&gt;30 (10.4% vs. 9.6%, p=0.0028). Amongst White patients, Hispanic ethnicity was associated with higher mean RS (18.3 [11.7] HW vs. 17.8 [10.6] NHW) and higher rate of RS&gt;30 (10.4% HW vs. 9.1% NHW, p&lt; 0.0001). There was no significant difference in mean RS between NHB and HB patients (19.0 [13.5] HB vs. 20.0 [12.7], p=0.1855) but there was a trend towards a lower proportion of RS&gt;30 in HB patients (10.8% HB vs. 14.6% NHB, p=0.0688. In patients with RS&gt;30, the proportion that received chemotherapy was similar based on ethnicity within White (80.7% HW vs. 82.3% NHW, p=0.1843) and Black (78.1% HB vs. 81.2% NHB, p=0.6601) patients. ET use was slightly lower in HW vs. NHW patients (90.6% vs. 91.7%, p&lt; 0.0001). There was no significant difference in ET use in NHB vs HB patients (89.9% vs. 89.9%, p=0.9651). Conclusions: In our examination of the early-stage breast cancer patients in the NCDB, Hispanic ethnicity was associated with higher RS amongst White patients with an opposite trend in Black women. Systemic therapy use was largely similar across ethnoracial categories. Future, studies should disaggregate Hispanic ethnicity by race to better understand tumor characteristics and clinical outcomes in this population.

Citation Format: Jose G. Bazan, Sachin R. Jhawar, Daniel Stover, Sasha Beyer, Julia White, Samilia Obeng-Gyasi. Understanding Ethnoracial Differences in Oncotype DX Recurrence Scores in Patients with Early-Stage Breast Cancer: An Analysis Based on Hispanic Ethnicity [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P3-05-60.

Abstract P1-10-10: Radiation Treatment Patterns for Elderly Women with Breast Cancer Brain Metastases

Background Breast cancer is the second most common cause of brain metastases (BM). Despite increasing incidence of BM in elderly patients, there is limited data on the optimal management of BM in this age group. In this study, we assessed the survival outcomes and treatment patterns of elderly breast cancer patients with BM (≥ 65 yo) treated at our institution and compared them to younger patients. Methods An IRB-approved single-institutional review of biopsy-proven breast cancer patients with BM treated with 1 to 5-fraction stereotactic radiation therapy (SRT) from 2015 to 2020 was performed. Primary endpoint was intracranial progression free survival (PFS) defined as time interval between end of SRT to date of first CNS progression. Secondary endpoints were overall survival (OS) from end of SRT, and radiation treatment patterns. Kaplan-Meier estimates, and Cox proportional hazard regression method were used for survival analyses. SPSS v26.0 was used for statistical analysis and p-value &lt; 0.05 was considered significant. Results A total of 115 metastatic breast cancer patients with BMs were included of which N=29 were ≥65 yo and N=86 were &lt; 65 yo. They received a total of 43 and 143 courses of stereotactic linac-based radiation therapy (RT) respectively to a mean number of 4.3 BM lesions (range 1-22). Median age at RT was 70 years (range 65-84) compared to 50.5 years (31-64) in younger patients. About 55.2% of elderly patients were ER/PR positive/Her2 negative (vs 24.4% in younger cohort), 31% were Her2 positive (vs 41.9%) and 13.8% were triple negative (vs 33.7%). Among patient characteristics, there was significant difference among elderly and young patients in hormone receptor status (p = 0.016); CNS only oligometastatic disease (0% vs 11.2%, p = 0.005); and the presence of extracranial disease at SRS (97.7% vs 79.7%, p &lt; 0.001). There was no significant difference between the two age groups in Karnofsky performance score (KPS) (62.7% vs 45.5% with KPS ≤ 80, p = 0.131), number of brain lesions treated (23.2% vs 30.1% with ≥ 5 BMs, p = 0.445), number of patients receiving prior whole brain radiotherapy (WBRT) (10.3% vs 19.8%, p = 0.062), surgery (23.2% vs 30.1%, p = 0.592), systemic therapy (including chemotherapy, targeted therapy and endocrine therapy) after SRT (86% vs 86.7%, p = 0.543), and salvage WBRT (10.3% vs 19.8%, p = 0.134). Median OS after RT was poorer in patients ≥ 65 yo compared to younger patients (7.9 months vs 14.4 months, p = 0.020), while intracranial PFS from RT was similar (8.5m vs 6.5m, p =0.345). The rates of freedom from neurological death and leptomeningeal disease (LMD) at 1 year were similar between the two groups (83.3% vs 87%, p = 0.780 and 87.6% vs 73.3%, p = 0.627, respectively). On univariate analysis, significant predictors of survival were age ≥65 yo (hazard risk, HR = 1.56), KPS &lt; 80 (HR = 1.69), extracranial progression at RT (HR = 2.44), systemic therapy after RT (HR = 0.28) and LMD (HR = 1.57). On multivariate analysis, age was not a significant factor for survival after adjusting for KPS, extracranial progression and systemic therapy. Conclusions Although elderly women had poorer OS than younger women, OS was similar after adjusting for KPS, extracranial progression and systemic therapy; and there was no difference in rates of intracranial PFS, neurological deaths and LMD in the different age groups. This study suggests that age alone may not play an independent role in treatment-selection and outcomes for breast cancer patients with BMs and personalized decision making including other clinical factors should be considered. Future studies are warranted to assess neurocognitive outcomes and other radiation treatment toxicities in elderly patients.

Citation Format: Rituraj Upadhyay, Haley K. Perlow, Nicole Williams, Brett Klamer, Julia White, Jose G. Bazan, Sachin R. Jhawar, Dukagjin M. Blakaj, John Grecula, Andrea Arnett, Evan Thomas, Arnab Chakravarti, Raju R. Raval, Maryam Lustberg, Joshua Palmer, Sasha Beyer. Radiation Treatment Patterns for Elderly Women with Breast Cancer Brain Metastases [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P1-10-10.

The Prognostic and Predictive Value of Genomic Assays in Guiding Adjuvant Breast Radiation Therapy

Many patients with non-metastatic breast cancer benefit from adjuvant radiation therapy after lumpectomy or mastectomy on the basis of many randomized trials. However, there are many patients that have such low risks of recurrence after surgery that de-intensification of therapy by either reducing the treatment volume or omitting radiation altogether may be appropriate options. On the other hand, dose intensification may be necessary for more aggressive breast cancers. Until recently, these treatment decisions were based solely on clinicopathologic factors. Here, we review the current literature on the role of genomic assays as prognostic and/or predictive biomarkers to help guide adjuvant radiation therapy decision-making.

Quality and Safety Considerations in Intensity Modulated Radiation Therapy: An ASTRO Safety White Paper Update

PURPOSE

This updated report on intensity modulated radiation therapy (IMRT) is part of a series of consensus-based white papers previously published by the American Society for Radiation Oncology (ASTRO) addressing patient safety. Since the first white papers were published, IMRT went from widespread use to now being the main delivery technique for many treatment sites. IMRT enables higher radiation doses to be delivered to more precise targets while minimizing the dose to uninvolved normal tissue. Due to the associated complexity, IMRT requires additional planning and safety checks before treatment begins and, therefore, quality and safety considerations for this technique remain important areas of focus.

METHODS AND MATERIALS

ASTRO convened an interdisciplinary task force to assess the original IMRT white paper and update content where appropriate. Recommendations were created using a consensus-building methodology, and task force members indicated their level of agreement based on a 5-point Likert scale, from "strongly agree" to "strongly disagree." A prespecified threshold of ≥75% of raters who select "strongly agree" or "agree" indicated consensus.

CONCLUSIONS

This IMRT white paper primarily focuses on quality and safety processes in planning and delivery. Building on the prior version, this consensus paper incorporates revised and new guidance documents and technology updates. IMRT requires an interdisciplinary team-based approach, staffed by appropriately trained individuals as well as significant personnel resources, specialized technology, and implementation time. A comprehensive quality assurance program must be developed, using established guidance, to ensure IMRT is performed in a safe and effective manner. Patient safety in the delivery of IMRT is everyone's responsibility, and professional organizations, regulators, vendors, and end-users must work together to ensure the highest levels of safety.

Reporting of Race and Hispanic Ethnicity in Breast Cancer Studies From the National Cancer Database

This cohort study characterizes the inclusion of Hispanic ethnicity or ethnoracial categories in breast cancer studies from the National Cancer Database.

Consensus Quality Measures and Dose Constraints for Breast Cancer from the Veterans Affairs Radiation Oncology Quality Surveillance Program and American Society for Radiation Oncology (ASTRO) Expert Panel

INTRODUCTION

Using evidence-based radiation therapy to direct care for patients with breast cancer is critical to standardizing practice, improving safety, and optimizing outcomes. To address this need, the Veterans Affairs (VA) National Radiation Oncology Program (NROP) established the VA Radiation Oncology Quality Surveillance Program (VAROQS) to develop clinical quality measures (QM). The VA NROP contracted with the American Society for Radiation Oncology (ASTRO) to commission five Blue-Ribbon Panels for breast, lung, prostate, rectal, and head & neck cancers.

METHODS

The Breast Cancer Blue-Ribbon Panel experts worked collaboratively with NROP to develop consensus QM for use throughout the VA system. establishing a set of quality measures for patients in several areas including: 1) consultation and work up, 2) simulation, treatment planning and treatment, and 3) follow up care. As part of this initiative, consensus dose volume histogram (DVH) constraints were outlined.

RESULTS

In total, 36 quality measures were established. Herein we review the process utilized to develop QM and final consensus QM pertaining to all aspects of radiation patient care as well as DVH constraints.

CONCLUSIONS

The QM and expert consensus DVH constraints are intended for ongoing quality surveillance within the VA system, centers providing community care for Veterans, and also available for use by the greater non-VA community measures of quality care for breast cancer patients receiving radiation.

Modified Radical Mastectomy in De Novo Stage IV Inflammatory Breast Cancer

BACKGROUND

There are few studies on surgical management in patients with de novo metastatic inflammatory breast cancer (IBC). The objective of this study is to examine the association between modified radical mastectomy (MRM) and disease-specific survival (DSS) in patients with de novo stage IV IBC.

PATIENTS AND METHODS

The Surveillance, Epidemiology, and End Result Program was queried for patients ≥18 years old with cT4d/pT4d pathology, histology type 8530 and 8533 with distant disease between 2010 and 2016. The sample was divided into two groups: (1) the MRM group, defined as MRM or mastectomy with at least ten lymph nodes removed, and (2) the no-surgery group. Sociodemographic and clinical variables were compared between the groups on bivariable analysis. After propensity score matching, Kaplan-Meier curves and a Cox proportional-hazards model examined DSS.

RESULTS

1293 patients were included in the study, of whom 240 underwent MRM. A higher percentage in the MRM group had only one metastatic site (69.8% versus 52.2%), received chemotherapy (88.3% versus 66.1%) and radiation (58.8% versus 26.0%) compared with the no-MRM group. MRM was associated with an increase in DSS compared with no MRM [HR 0.63 (95% CI 0.50-0.80), p < 0.001]. Patients with MRM had a 5-year DSS rate of 31.4% compared with 17.7% for patients not undergoing surgery (p = 0.001). Survival time was 38 months (range 27-45 months) for the MRM group versus 27 months (22-29 months) for the no-MRM group.

CONCLUSION

MRM in patients with de novo metastatic IBC may improve DSS in a subset of patients.

NRG-BR002: A phase IIR/III trial of standard of care systemic therapy with or without stereotactic body radiotherapy (SBRT) and/or surgical resection (SR) for newly oligometastatic breast cancer (NCT02364557)

1007

Background: Prospective and retrospective studies of patients (pts) with oligometastatic (OM) disease have supported that metastases (mets) directed treatment (MDT) with SBRT or SR in addition to standard of care systemic therapy (SOC ST) can improve progression-free (PFS) and overall survival (OS) compared with SOC ST alone. However, randomized evidence in oligometastatic breast cancer (OMBC) are lacking. NRG-BR002, a randomized Phase IIR/III trial, sought to determine the efficacy of SOC ST + MDT (SBRT or SR) as first line treatment of OMBC. Methods: OMBC pts with ≤ 4 extracranial mets on standard imaging with controlled primary disease were eligible if on first line SOC ST for ≤ 12 months without progression. Pts were randomized (1:1) to ARM 1 – SOC ST (mainly chemotherapy, endocrine therapy, anti-HER2) or ARM 2 – SOC ST with MDT of all mets. Stratification included mets number (1 vs > 1), ER/PR and Her2 status, and chemotherapy use. Phase IIR targeted sample size was 128 total/116 eligible pts, for 92% power and 1-sided significance level = 0.15 to determine if adding MDT shows a signal for improved PFS (hazard ratio [HR] = 0.55, corresponding to median PFS (mPFS) from 10.5 to 19 months), in order to continue to the full phase III trial for OS. PFS and OS were estimated by Kaplan-Meier and arms compared with log-rank. Results: 125 of the 129 pts randomized were eligible (ARM 1 = 65, ARM 2 = 60). Key characteristics included median age 54, 79% ER+ or PR+/HER2-, 13% HER2+, 8% triple negative. 60% had 1 metastasis and 20% presented synchronously with primary disease. Following randomization, systemic therapy was delivered to 95% in ARM 1 and 93% in ARM 2; ablation: SBRT 93%, SR 2%, and 5% none. The median follow-up was 30 mo. The mPFS (70% CI) in ARM 1 was 23 mo (18, 29) and 19.5 mo (17, 36) in ARM 2; 24 and 36-mo PFS (70% CI) for ARM 1 were 45.7% (38.9, 52.5) and 32.8% (26.0, 39.5) compared with 46.8 (39.2, 54.3) and 38.1 (29.7, 46.6) in ARM 2; HR (70% CI): 0.92 (0.71, 1.17); and 1-sided log-rank p = 0.36. As PFS did not show signal, OS reporting is included: median OS was not reached in either arm; 36-mo OS (95% CI) in ARM 1 71.8% (58.9, 84.7) and ARM 2 68.9% (55.1, 82.6; 2-sided log-rank p = 0.54). Analysis of first failure showed new mets outside index area (Arm 1) /RT field (Arm 2) developed similarly in both arms at 40%. There were fewer new mets inside treated/index area for Arm 2 6.7% vs ARM 1 29.2%, respectively. There were no grade 5 treatment-related adverse events (AEs), 1 grade 4 AE in ARM 1, and 9.7% and 5.3% grade 3 AEs in ARMS 1 and 2, respectively. Circulating tumor cell counts (0 vs ≥1) at baseline were similar in both arms and were not prognostic HR (95% CI): 1.04 (0.54, 2.02). Conclusions: The addition of MDT to SOC ST did not show signal for improved PFS, nor OS difference in patients with OMBC. The trial will not proceed to the Phase III component. Clinical trial information: NCT02364557.

Abstract P3-19-17: Radiation of the low axilla in the prone position

Background: Whole breast irradiation (WBI) after a positive sentinel lymph node biopsy (SNB) is recommended to be treated in the supine position to facilitate inclusion of the low axilla with “high tangents” when regional nodal irradiation is not planned. Treatment in the prone position has several advantages over supine positioning including minimizing heart and lung doses for many and decreased skin toxicity for larger breasted women. We hypothesized that, using three dimensional conformal radiation therapy (3DCRT), the low axilla can be safely and adequately treated in the prone position with minimal toxicity and good outcomes. Methods: We identified patients who underwent post lumpectomy whole breast and low axilla irradiation in the prone position using 3DCRT from 2014 to 2020. Standard 3DCRT treatment planning included delineation of surgical cavity, breast and low axillary clinical target volumes (CTV) with 5 mm expansion to planning target volumes (PTV). The “low axilla” CTV was generally defined as the level I axilla according to the RTOG Breast Cancer Atlas. Dosimetric data for both targets and organs at risk (OARs) was extracted from approved treatment plans’ dose-volume histograms (DVHs). Toxicity and cancer outcomes were collected from the electronic medical records. Descriptive statistical analysis was performed. Results: Seventy patients were identified. Median age was 61 years (range 34-87), median body mass index (BMI) was 30.4 kg/m2 (range 22.1-49.1), and 88.6% (N=62) had hormone sensitive, HER2 negative breast cancer. The median tumor size was 1.35 cm (range 0.07-4.5cm). For 56 patients (80.0%), a SNB was done with median of 2 (range 1-7) sentinel nodes removed - 19 (34%) with macro-metastasis (median size 4 mm, range 2.2-13mm), 21 (37.5%) with micrometastasis, and 16 (28.6%) with isolated tumor cells. Three patients had an additional node with isolated tumor cells. Thirteen (18.6%) were Nx (no nodal evaluation) and 1 had an unsuccessful SLNB with no lymph nodes obtained. Hypofractionation was used in 97.1% (N=68): 4256 cGy in 16 fractions (N=44, 62.8%) or 4000 cGy in 15 fractions (N=24, 34.3%). All targets were covered adequately. The median V95/V90 of the PTVbreast_eval, PTVlump_eval, and PTVAx were 96%/98.3% (range 76.2/91.9% - 99.6/101.4%), 100.1%/101.2% (range 87.6/94.9%-102.8/103.3%), and 95.3%/97.5% (range 82.4/91.6%-100.4/101.7%) respectively. The mean heart dose for all patients was 83.5 cGy; 82.7 cGy for right-sided tumors and 83.8 cGy for left-sided tumors. The median V16 of the ipsilateral lung was 4.25% (range 0.2 - 11.3%). Overall, toxicity was low with no grade 3 or higher events. For acute toxicity, most patients (N=54, 77.1%) reported grade 1 fatigue and had either grade 1 (N=52, 74.2%) or grade 2 (N=15, 21.4%) dermatitis. For late toxicity, 14 patients (20%) were referred to physical therapy after radiation, 7 (10%) for range of motion, 5 (7%) for arm lymphedema evaluation and 4 (6%) for other reasons. With a median follow-up of 18.5 months (range 0-63 months), 1 patient recurred both locally and regionally (1.4%) and one other patient recurred distantly. Conclusions: Patients with a positive SNB or are Nx who are recommended to have post-lumpectomy whole breast and low axilla irradiation can be safely and adequately treated in the prone position using 3DCRT with minimal toxicity and good outcomes.

Citation Format: Victoria Doss, Erin Healy, Sasha Beyer, Sachin R. Jhawar, Jose G. Bazan, Julia White. Radiation of the low axilla in the prone position [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 P3-19-17.

Abstract P3-19-08: Breast cancer related lymphedema in patients undergoing RNI: Is the axillary lateral vessel thoracic junction an organ-at-risk?

Background: Breast-cancer related lymphedema (BCRL) is a devastating treatment complication driven by the extent of axillary surgery (axillary lymph node dissection [ALND] versus sentinel lymph node biopsy [SLNB]). Regional nodal irradiation (RNI) may increase the risk of BCRL by up to 5%. Recently, investigators identified a region of the axilla known as the axillary-lateral thoracic vessel juncture (ALTJ) as a potential organ-at-risk (OAR) demonstrating that increasing radiation dose to the ALTJ was associated with a higher risk of BCRL. Here, we set to validate whether radiation dose to the ALTJ is associated with BCRL. Materials/Methods: We identified patients with stage II-III breast cancer treated with adjuvant RNI after M or L from 2013-2018 excluding those with BCRL pre-radiation. RNI treatment planning included delineation of clinical target volumes (CTVs): breast or chest wall and regional lymph nodes per the RTOG Breast Cancer Atlas. The CTVs were expanded by 5mm to create the planning target volume (PTV). Dose delivered was 50 Gy/25 fractions with goal of 47.5 Gy (95%) to 95% of each PTV. We defined BCRL as difference in arm circumference between the ipsilateral and contralateral limb &gt;2.5 cm at any 1 visit or ≥2 cm on at least 2 visits. All patients suspected of having BCRL at routine follow-up visits were evaluated by physical therapy. The ALTJ was retrospectively contoured and the following metrics collected: maximum/minimum/mean dose; V10Gy-V50Gy. Follow-up time was defined as the time from surgery to the development of BCRL or last follow-up. Cox proportional hazards regression models were used to test the association between clinical and dosimetric parameters with the development of BCRL. All variables with p&lt;0.10 on univariate analysis were entered in the final multivariate model (p&lt;0.05 considered statistically significant). Results: Population includes 378 patients with median age 53 years (interquartile range [IQR], 45-61 years), median body mass index (BMI) 28.4 kg/m2 (IQR, 24.3-33.4 kg/m2), 60% HR+/HER2-, 89% chemotherapy, 53% stage III, 71% underwent M, and 82% underwent ALND with median of 18 nodes removed (IQR, 11-25) and median of 2+ nodes (IQR, 1-5). Median follow-up time was 54.5 months (IQR, 40.3-72.2 months). The ALTJ and axilla PTV overlapped in 91% of the patients. BCRL developed in 97 patients (25.7%) at a median of 18.9 months (IQR, 9.9-30.6 months). The 4-year cumulative incidence of BCRL was 23.5% (26.6% ALND vs. 8.7% SLNB, p=0.002). On univariate analysis, increasing age (HR=1.02, p=.039), increasing BMI (HR=1.04, p=0.002), increasing number of nodes removed (HR=1.04, p&lt;0.0001), and use of IMRT vs. 3DCRT (HR=1.50, p=0.041) were all significantly associated with developing BCRL while increasing size of the axilla PTV (HR=0.96, p=0.047) was associated with a lower risk. None of the ALTJ metrics were associated with developing BCRL. Increasing ALTJ V45 was marginally associated with a lower risk of BCRL (HR=0.96, p=0.091). On multivariate analysis, increasing age (HR=1.02, p=0.021), increasing BMI (HR=1.04, p=0.004), and increasing number of nodes removed (HR=1.03, p=0.001) were associated with a higher risk of developing BCRL while use of IMRT (HR=1.24, p=0.338), size of the axilla PTV (HR=0.96, p=0.110) and ALTJ V45 (HR=0.99, p=0.708) were not. There were 10 local-regional recurrence (LRR) events as a first failure, 8 of which occurred with simultaneous distant metastases (DM). Of these LRRs, 5 included an axillary nodal component (all with DM) resulting in a 2.6% 4-year LRR rate (1.4% axillary recurrence rate). Conclusion: In this analysis, ALTJ is not validated as a critical OAR for reducing BCRL risk. Until such an OAR is discovered, the axillary PTV should not be modified or dose reduced in efforts to reduce BCRL given the low LRR and inability to validate ALTJ as an OAR.

Citation Format: Erin Healy, Sachin Jhawar, Sasha Beyer, Julia R White, Jose G Bazan. Breast cancer related lymphedema in patients undergoing RNI: Is the axillary lateral vessel thoracic junction an organ-at-risk? [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 P3-19-08.

Abstract P3-19-09: Impact of intraoperative radiation therapy and external beam radiation therapy on non-breast cancer mortality in early-stage breast cancer

Purpose: The TARGIT-A trial of kilovoltage intraoperative radiation therapy (IORT) versus external beam radiation therapy (EBRT) demonstrated a significant reduction in non-breast cancer mortality (nBCM) in women that received IORT, largely attributed to an increase in cardiac mortality in patients that received EBRT. Further, If EBRT does result in excess nBCM due to cardiac or other causes, then treatment with lumpectomy (Lump) alone or mastectomy (Mast) alone should result in lower rates of nBCM rates compared to Lump+EBRT. Our primary objective was to determine whether Lump+EBRT results in increased nBCM compared to Lump+IORT in women with early-stage breast cancer (BC) with a hypothesis that the two approaches should result in equivalent nBCM. We also tested the hypotheses that Lump+EBRT should have the same rates of nBCM as Lump alone or Mast alone. Materials/Methods: We used the Surveillance Epidemiology and End Results (SEER) database to identify women with early-stage BC treated with Lump alone, Lump+EBRT, Lump+IORT, or Mast alone from 2000-2016. SEER does not distinguish between kilovoltage IORT and electron IORT. We included patients with characteristics similar to the TARGIT-A study: age≥45 years; ductal carcinoma in situ (DCIS) or T1; lymph-node negative. We excluded patients that: received chemotherapy; received postmastectomy radiation therapy; had unknown cause of death; and had ≤1 month of follow-up. The primary endpoint was nBCM which is captured in the SEER database (patients were censored if they were alive or dead due to cancer at last follow-up). Cox-proportional hazards multivariate regression models were used to compare nBCM between Lump+EBRT and Lump+IORT adjusting for confounders that were statistically significant on univariate analysis. We secondarily compared nBCM in the Lump+EBRT vs. Lump population and Lump+EBRT vs. Mast population. Results: We identified 219,470 women that met the inclusion criteria: 121,776 Lump+EBRT; 1,735 Lump+IORT; 41,900 Lump; 54,059 Mast. Median follow-up time was 61 months for the entire cohort (IQR, 30-99 months) but was shorter for Lump+IORT patients (29 months) compared to the other groups (63 months Lump+EBRT; 62 months Mast; 57 months Lump). There were a total of 16,640 nBCM events: 6,210 Lump+EBRT; 5,708 Lump; 4,704 Mast; 18 Lump+IORT. The 5-year cumulative incidence of nBCM was 3.1% for Lump+EBRT vs. 1.6% for Lump+IORT (p=0.034). After adjustment for potential confounders (age, tumor location, marital status, race/ethnicity, DCIS vs. invasive, tumor grade, hormone receptor status, and receipt of axillary surgery), patients treated with Lump+IORT had a 38% relative reduction in the risk of nBCM compared to those treated with Lump+EBRT (HR=0.62, 95% CI 0.39-0.99, p=0.045). Other factors associated with increased nBCM included older age, divorced/single/widowed status (vs. married), Black race, high tumor grade, receipt of axillary lymph node dissection (vs. sentinel lymph node biopsy), no axillary surgery (vs. sentinel node biopsy), and ER-/PR- disease (vs. ER+ or PR+). In contrast, patients treated with Lulmp+EBRT had lower nBCM compared to those that received Lump alone (adjusted HR=0.55, 95% CI 0.53-0.57, p&lt;0.0001) and compared to those that received Mast alone (adjusted HR=0.59, 95% CI 0.56-0.61, p&lt;0.0001). Conclusion: In summary, contrary to our hypothesis, we found that Lump+IORT was associated with lower nBCM compared to Lump+EBRT possibly reflecting underlying selection bias. However, Lump+EBRT was not associated with an increased nBCM relative to patients treated with Lump alone or Mast alone. This suggests that the underlying mechanism for the reduced nBCM seen in patients treated with IORT in the TARGIT-A trial and this SEER analysis is not due to the potentially harmful effects of EBRT.

Citation Format: Jose G Bazan, Jay Fisher, Sachin Jhawar, Erin Healy, Sasha Beyer, Julia R. White. Impact of intraoperative radiation therapy and external beam radiation therapy on non-breast cancer mortality in early-stage 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 P3-19-09.

Abstract P3-19-02: Should deep inspiration breath hold scans be standardly acquired for right-sided breast/chestwall and regional nodal irradiation?

Background: Adjuvant regional nodal irradiation (RNI) after breast conserving surgery or mastectomy is supported by clinical trials for patients with node-positive breast cancer. RNI results in increased radiation dose to organs-at-risk (OARs) such as the heart and lungs. While regular acquisition of both free breathing (FB) and deep inspiration breath hold (DIBH) scans has been widely adopted for left-sided breast cancers (LBCs) as a cardiac-sparing technique, DIBH scans are not routinely acquired for right-sided breast cancers (RBCs). Therefore, when OAR constraints cannot be met with 3D conformal radiation therapy (3DCRT) planning on the FB scan, the only option is intensity modulated radiation therapy (IMRT), with its inherent increased cost, resource utilization, and requirement for insurance authorization. Given these challenges, we have regularly acquired FB and DIBH scans for right-sided RNI since 2018. We hypothesized that acquisition of DIBH scans would result in a reduced need for IMRT and reduced dose to OARs. Methods: We retrospectively identified patients who were treated with right-sided RNI who had both FB and DIBH scans. All patients had target volumes (breast or chest wall and regional lymph nodes [undissected axillary, supraclavicular, and internal mammary nodes]) prospectively contoured on the FBCT scan based upon the RTOG Breast Atlas. This initiated a treatment planning algorithm that began with creating a FB 3DCRT plan and changed to DIBH 3DCRT then FB IMRT when OAR constraints could not be met while maintaining acceptable planning target volume (PTV) coverage. For patients who did not have contours available on the DIBH scan, the treating physician retrospectively completed the PTV contours. For each patient, three total plans were created for comparison using our institutional target coverage and OAR metrics: FB 3DCRT, FB IMRT, and DIBH 3DCRT. We compared PTV coverage and doses to multiple OARs including the contralateral breast, esophagus, heart, lungs (left, right, total lung dose), and liver. PTV coverage and OAR doses were evaluated by a one-way ANOVA followed by Bonferroni comparison. A p &lt; 0.05 was considered statistically significant.Results: We identified 38 patients in whom FB and DIBH scans were acquired. Only 32% (N=12) were treated with the standard FB 3DCRT. Of the remaining 26 patients 73% (N=19) were treated DIBH 3DCRT, and only 27% (N=7) were treated with FB IMRT, resulting in a FB IMRT rate of 18% overall. Without DIBH scans, 68% (N=19) would have advanced to FB IMRT. Dosimetric comparison across these 38 patients (N=114 plans) demonstrated that DIBH 3DCRT had at least equivalent OAR metrics as compared to FB 3DCRT, with significant improvement in max heart dose (9.6 Gy vs. 14.9 Gy; p = 0.034), right lung V20 (32.1% vs 37.8%; p &lt; 0.01), mean total lung dose (8.9 Gy vs. 10.5 Gy; p &lt; 0.01), and mean liver dose (1.8 Gy vs. 4.0 Gy; p &lt; 0.01). FB IMRT plans resulting in significantly lower right lung V20 (26.3% FB IMRT vs. 37.8% FB 3DCRT vs. 32.1% DIBH 3DCRT), but resulted in higher dose to the heart and contralateral breast: mean heart dose (2.2 Gy FB IMRT vs. 1.0 Gy FB 3DCRT vs. 0.9 Gy DIBH 3DCRT; p &lt; 0.01), maximum heart dose (16.4 Gy FB IMRT vs. 14.9 Gy FB 3DCRT vs. 9.6 Gy DIBH 3DCRT; p &lt; 0.01) and contralateral breast D5% (5.0 Gy FB IMRT vs. 2.9 Gy FB 3DCRT vs. 3.0 Gy DIBH 3DCRT; p &lt; 0.01).Conclusions: We found that acquiring DIBH scans for RBC patients receiving RNI reduced the need for FB IMRT from 68% to 18%. As compared to FB 3DCRT, DIBH 3DCRT resulted in in equivalent target coverage with significantly lower lung and liver doses. FB IMRT is useful to keep the right lung V20 within acceptable limits at the expense of higher dose to other OARs. Our data support the routine acquisition of DIBH scans in RBC patients undergoing RNI in order to decrease the proportion of patients that require FB IMRT.

Citation Format: Sachin R Jhawar, Kylee Lindsey, Karla Kuhn, Kayla Tedrick, Ian Zoller, William Taylor, Eric Cochran, Erin Healy, Sasha Beyer, Julia White, Jose G Bazan. Should deep inspiration breath hold scans be standardly acquired for right-sided breast/chestwall and regional nodal irradiation? [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 P3-19-02.

Lack of Cardiotoxicity Endpoints in Prospective Trials Involving Chest Radiation Therapy: A Review of Registered, Latter-Phase Studies

BACKGROUND

Chest radiation therapy (RT) has been associated with increased cardiac morbidity and mortality in numerous studies including the landmark Darby study published in 2013 demonstrating a linear increase in cardiac mortality with increasing mean heart radiation dose. However, the extent to which cardiotoxicity has been incorporated as an endpoint in prospective RT studies remains unknown.

METHODS

We queried clincaltrials.gov to identify phase II/III trials in lung, esophageal, lymphoma, mesothelioma, thymoma, or breast cancer from 1/1/2006-2/1/2021 enrolling greater than 100 patients wherein chest RT was delivered in at least one treatment arm. The primary endpoint was the rate of inclusion of cardiotoxicity as a specific primary or secondary endpoint in the pre- (enrollment started prior to 1/1/2014) versus post-Darby era using the Chi-square test (p<0.05 considered significant). We also analyzed clinical trial factors associated with the inclusion of cardiotoxicity as an endpoint using logistic regression analysis.

RESULTS

In total, 1,822 trials were identified, of which 256 merited inclusion. 32% were for esophageal, 31% lung, 28% breast, and 7% lymphoma/thymoma/mesothelioma cancers, respectively. 5% (N=13) included cardiotoxicity as an endpoint: 6 breast cancer, 3 lung cancer, 3 esophageal cancer, and 1 lymphoma study. There was no difference in the inclusion of cardiotoxicity endpoints in the pre-Darby versus post-Darby era (3.9% vs. 5.9%, P=0.46). The greatest absolute increase in inclusion of cardiotoxicity as an endpoint was seen for lung cancer (0% vs. 6%, p=0.17) and breast cancer (5.7% vs. 10.8%, p=0.43) studies, though these increases remained statistically non-significant. We found no clinical trial factors associated with the inclusion of cardiotoxicity as an endpoint.

CONCLUSIONS

Among prospective trials involving chest RT, cardiotoxicity remains an uncommon endpoint despite its prevalence as a primary source of toxicity following treatment. In order to better characterize cardiac toxicities, future prospective studies involving chest RT should include cardiotoxicity endpoints.

Disparate Use of Chemoradiation in Elderly Patients With Localized Anal Cancer

BACKGROUND

The incidence of squamous cell carcinoma of the anus (SCCA) is increasing, particularly among the elderly (age ≥65 years). We sought to compare patterns of care for the treatment of SCCA in elderly versus nonelderly patients.

METHODS

Data for patients with stages I-III SCCA diagnosed from 2004 through 2015 were obtained from the National Cancer Database. Patients were categorized as having received standard-of-care (SOC) chemoradiation (CRT) with multiagent chemotherapy, non-SOC therapy, palliative therapy, or no treatment. Differences in treatment groups were tested using the chi-square test. We used logistic regression to identify predictors of SOC CRT and multiagent versus single-agent chemotherapy in patients receiving CRT. Propensity score matching was used to compare overall survival (OS) in elderly patients receiving multiagent versus single-agent chemotherapy for those receiving CRT.

RESULTS

We identified 9,156 elderly and 17,640 nonelderly patients. A lower proportion of elderly versus nonelderly patients (54.5% vs 65.0%; P<.0001) received SOC CRT than other treatments or no treatment. In multivariate analysis, elderly patients were 38% less likely than nonelderly patients to receive SOC CRT (odds ratio, 0.62; 95% CI, 0.58-0.65; P<.0001). A higher proportion of the elderly were treated with single-agent versus multiagent chemotherapy (16.9% vs 11.8%; P<.0001), which resulted in a >1.5-fold increase in the likelihood of elderly patients receiving single-agent chemotherapy (odds ratio, 1.52; 95% CI, 1.39-1.66) in multivariate analysis. After propensity score matching, 3-year OS was higher in elderly patients who received CRT with multiagent versus single-agent chemotherapy (77.1% vs 67.5%; hazard ratio, 0.78; 95% CI, 0.68-0.89; P=.0002).

CONCLUSIONS

In this comprehensive study of patients with stages I-III SCCA, elderly patients were less likely than nonelderly patients to receive SOC CRT. The low proportion of elderly patients receiving SOC CRT with multiagent chemotherapy for localized anal cancer suggests that the optimal treatment approach for this vulnerable population remains undefined.

De-escalation of radiation therapy in patients with stage I, node-negative, HER2-positive breast cancer

In the modern era, highly effective anti-HER2 therapy is associated with low local-regional recurrence (LRR) rates for early-stage HER2+ breast cancer raising the question of whether local therapy de-escalation by radiation omission is possible in patients with small-node negative tumors treated with lumpectomy. To evaluate existing data on radiation omission, we used the National Cancer Database (NCDB) to test the hypothesis that RT omission results in equivalent overall survival (OS) in stage 1 (T1N0) HER2+ breast cancer. We excluded patients that received neoadjuvant systemic therapy. We stratified the cohort by receipt of adjuvant radiation. We identified 6897 patients (6388 RT; 509 no RT). Patients that did not receive radiation tended to be ≥70 years-old (odds ratio [OR] = 3.69, 95% CI: 3.02-4.51, p < 0.0001), to have ≥1 comorbidity (OR = 1.33, 95% CI: 1.06-1.68, p = 0.0154), to be Hispanic (OR = 1.49, 95% CI: 1.00-2.22, p = 0.049), and to live in lower income areas (OR = 1.32, 95% CI: 1.07-1.64, p = 0.0266). Radiation omission was associated with a 3.67-fold (95% CI: 2.23-6.02, p < 0.0001) increased risk of death. While other selection biases that influence radiation omission likely persist, these data should give caution to radiation omission in T1N0 HER2+ breast cancer.

Analysis of Radiation Dose to the Shoulder by Treatment Technique and Correlation With Patient Reported Outcomes in Patients Receiving Regional Nodal Irradiation

Background/Purpose

Shoulder/arm morbidity is a late complication of breast cancer treatment with surgery and regional nodal irradiation (RNI). We set to analyze the impact of radiation technique [intensity modulated radiation therapy (IMRT) or 3D conformal radiation therapy (3DCRT)] on radiation dose to the shoulder with a hypothesis that IMRT use results in smaller volume of shoulder receiving radiation. We explored the relationship of treatment technique on long-term patient-reported outcomes using the quick disabilities of the arm, shoulder, and hand (q-DASH) questionnaire.

Materials/Methods

We identified patients treated with adjuvant RNI (50 Gy/25 fractions) from 2013 to 2018. We retrospectively contoured the shoulder organ-at-risk (OAR) from 2 cm above the ipsilateral supraclavicular (SCL) planning target volume (PTV) to the inferior SCL PTV slice and calculated the absolute volume of shoulder OAR receiving 5–50 Gy (V5–V50). We identified patients that completed a q-DASH questionnaire ≥6 months from the end of RNI.

Results

We included 410 RNI patients: 54% stage III, 72% mastectomy, 35% treated with IMRT. IMRT resulted in significant reductions in the shoulder OAR volume receiving 20–50 Gy vs. 3DCRT. In total, 82 patients completed the q-DASH. The mean (SD) q-DASH=25.4 (19.1) and tended to be lower with IMRT vs. 3DCRT: 19.6 (16.4) vs. 27.8 (19.8), p=0.078.

Conclusion

We found that IMRT reduces radiation dose to the shoulder and is associated with a trend toward reduced q-DASH scores ≥6 months post-RNI in a subset of our cohort. These results support prospective evaluation of IMRT as a technique to reduce shoulder morbidity in breast cancer patients receiving RNI.

Abstract PS15-04: De-escalation of radiation therapy in patients with stage I, node-negative, HER2-positive breast cancer: Patterns of care and survival outcomes using the national cancer database

Background: In the modern era, highly effective anti-HER2 therapy is associated with very low local-regional recurrence (LRR) rates for early-stage HER2+ breast cancer. One recent prospective study of T1-2N0 HER2+ breast cancer patients treated with lumpectomy and adjuvant paclitaxel+trastuzumab followed by whole breast radiation (RT) demonstrated 7-year LRR-free survival of 99% raising the question of whether local therapy de-escalation by RT omission is possible. To evaluate existing data on radiation omission, we used the National Cancer Database (NCDB) to test the hypothesis that RT omission results in equivalent overall survival (OS) in stage 1 (T1N0) HER2+ breast cancer.Materials/Methods: We identified patients with stage I (T1N0) HER2+ breast cancer treated with lumpectomy, adjuvant chemotherapy and anti-HER2 therapy from 2013 (the first year anti-HER2 therapy receipt was reliably collected) to 2015. We excluded patients that received neoadjuvant systemic therapy. We then stratified the cohort by receipt of adjuvant RT. The primary endpoint was OS as LRR is not captured by the NCDB. OS was analyzed by the Kaplan-Meier method (RT and RT omission groups compared by the log-rank test) and multivariate cox regression including variables with p&lt;0.20 on univariate analysis (hazard ratios [HR], and 95% confidence intervals [CI] are reported). Propensity score matched (PSM) analysis with patients matched on age (≥70 vs. &lt;70), comorbidities (≥1 vs. 0), grade (3 vs. 1-2), tumor size (&gt;1 cm vs. ≤1 cm), ER/PR status (ER-/PR- vs. ER+ and/or PR+), facility type (academic vs. non-academic), and income (&lt;$46,000/yr vs. ≥46,000/yr) was performed as an independent test of the Cox regression analysis.Results: We identified 6,897 patients that met the study criteria (6,388 RT; 509 no RT). Patients that did not receive RT tended to be older (mean age 64.0 years v. 59.2 years, p&lt;0.0001), have ≥1 comorbidity (21.4% vs. 14.8%, p&lt;0.0001), and live in lower income areas (60.1% vs. 52%, p=0.0004). Median follow-up was 29.4 months (IQR=19.5-39.9 months) with 155 deaths (95 RT; 60 RT omission). The 2-year OS was significantly worse for patients with RT omission (89.0% vs. 99.2%, p&lt;0.0001). Factors associated with OS on univariate analysis included RT omission (p&lt;0.0001), age≥70 (p&lt;0.0001), ≥1 comorbidity (p=0.0002), tumor size&gt;1cm (p=0.14), grade 3 tumors (p=0.14), academic facility (p=0.16) and lower income (p=0.02) but not ER-/PR- status (HR=1.01, p=0.95), distance to treatment facility (p=0.42) or tumor laterality (p=0.66). On multivariate analysis, RT omission (HR=7.55, 95% CI 5.36-10.63, p&lt;0.0001), age≥70 (HR=2.30, 95% CI 1.63-3.23, p&lt;0.0001), and ≥1 comorbidity (HR=1.45, 95% CI 1.00-2.09, p=0.05) remained independently associated with higher risk of death. The PSM cohort consisted of 509 pairs of patients with 73 deaths (13 RT; 60 RT omission) and median follow-up 26.4 months (IQR, 16.5-37.3 months). RT omission remained associated with a 5.42-fold (95% CI 3.02-9.73, p&lt;0.0001) increased risk of death in the PSM cohort.Conclusion: This study demonstrates that RT omission is independently associated with an increased risk of death in patients with stage I, HER2+, node-negative breast cancer treated with lumpectomy, adjuvant chemotherapy and anti-HER2 therapy. Patients that did not receive RT tended to be older, have more comorbidities and live in lower income areas. While other selection biases that influence RT omission likely persist, these data should give caution to RT omission in stage I, node-negative HER2+ breast cancer.

Citation Format: Jose G Bazan, Sachin Jhawar, Daniel Stover, Ko Un Park, Sasha Beyer, Erin Healy, Julia R White. De-escalation of radiation therapy in patients with stage I, node-negative, HER2-positive breast cancer: Patterns of care and survival outcomes using the national cancer database [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS15-04.

Abstract SS2-05: Emerging from COVID-19 pandemic: Provider perspective on use of neoadjuvant endocrine therapy (NET) in early stage hormone receptor positive breast cancer

IntroductionDuring the coronavirus 2019 (COVID-19) pandemic in USA, NET use has been recommended to allow safe deferral of surgical treatment in early stage, estrogen receptor positive breast cancer (ER+BC). In such circumstances, after NET use there is limited guidance on locoregional treatment, especially with management of the axilla. We aimed to evaluate patterns of care in early stage ER+BC during the first several months of the COVID-19 pandemic.MethodA cross-sectional, 30-item survey was developed using a standardized survey development framework. The survey was administered May 8 - June 12, 2020 to a convenience sample of medical oncologists (MO), radiation oncologists (RO), and surgeons (SO) - breast committee members of two national cooperative groups (Alliance and SWOG) with additional participation through chain referrals. Providers were presented with general questions on NET use before and during the pandemic. They were asked their propensity for omitting axillary lymph node dissection (ALND) after NET if 1 micrometastatic node is found on sentinel lymph node biopsy, based on duration of NET.Results114 providers from 29 US states completed the survey - 42 (37%) MO, 14 (12%) RO, and 58 (51%) SO, the majority (N=73/96, 76%) with practices dedicated ≥ 75% to BC, at NCI designated comprehensive cancer centers 52% (N=48/94) and in large cities (N=49/94, 52%). Prior to COVID-19, most rarely (N=49/107, 46%) or sometimes (N=36, 33%) used NET for early stage ER+BC. Nearly half were willing to delay surgery up to 2 months (46%) and 3 months (21%) without use of NET (Table 1, †p&lt;0.05). Most providers would perform a genomic assay on the biopsy specimen on all or select patients prior to NET initiation, more frequently by MO compared to RO and SO (90% vs. 75% and 60%, p&lt;0.05). The most preferred regimen was tamoxifen (without ovarian suppression) for premenopausal patients and aromatase inhibitor for postmenopausal patients. Most planned to use NET for as little time as possible until surgery could proceed. When stratified by specialty, more MO stated they would vary the duration of therapy based on patient’s risk of cancer progression. Most providers recommended omitting ALND after 1, 2, or 3 months of NET (1 month N=56/93, 60%; 2 months N=54/92, 59%; 3 months N=48/90, 53%). With longer duration of therapy, the propensity for omitting ALND decreased (definitely omit after 6 months N=25/91, 27%; probably omit after 6 months N=38/91, 42%; definitely omit after 1 year N=26/92, 28%; probably omit after 1 year N=29/92, 32%). Omitting ALND was not associated with provider’s years in practice, percent of practice dedicated to BC, practice type or setting, participation in multidisciplinary tumor board, or number of COVID-19 cases in the provider’s practicing state.ConclusionMost providers changed their management of early stage ER+BC during the COVID-19 pandemic by utilizing NET until surgery could proceed. As the duration of NET extended, more providers favored ALND in low volume axillary metastatic disease in early stage ER+BC. Additional data to inform the care on post-NET locoregional management is needed.

Table 1. Management of early stage, node negative, ER+BC during COVID-19 pandemicTotal (N, %)Med OncRad OncSurgeonHow long are you willing to delay surgery (without use of endocrine therapy)?Up to 1 month25 (23%)10 (24%)015 (26%)Up to 2 months51 (46%)17 (40%)7 (64%)27 (47%)Up to 3 months23 (21%)9 (21%)2 (18%)12 (21%)Up to 4 months3 (3%)2 (5%)1 (9%)0Up to 6 months8 (7%)4 (10%)1 (9%)3 (5%)Have you changed your practice during the current pandemic?Yes - institution mandated change to delay surgery8 (25%)4 (36%)04 (29%)Yes - based on multidisciplinary team discussion (no explicit institutional mandate to delay cancer surgery)21 (66%)6 (55%)7 (100%)8 (57%)No - was not allowed by institution to change0000No - was not necessary3 (9%)1 (9%)02 (14%)If using endocrine therapy before surgery, which regimen are you using?†Tamoxifen for all patients0000Tamoxifen for premenopausal patients; aromatase inhibitor for postmenopausal patients77 (81%)26 (63%)051 (94%)Ovarian suppression with aromatase inhibitor for premenopausal patients; aromatase inhibitor for postmenopausal patients18 (19%)15 (37%)03 (6%)How are you staging the axilla prior to starting endocrine therapy?Exam only28 (26%)8 (19%)2 (17%)18 (33%)Exam + US77 (71%)30 (71%)10 (83%)37 (67%)Exam + US + cross sectional image (CT scan)4 (4%)4 (10%)0 (0%)0 (0%)SLNB0000If using endocrine therapy first (before surgery), are you†Sending genomic assay on biopsy specimen on all patients28 (26%)18 (44%)1 (8%)9 (16%)Sending genomic assay on biopsy specimen on only select patients (ie. high grade, size on imaging/exam, high Ki-67)51 (48%)19 (46%)8 (67%)24 (44%)Not sending genomic assay. Using PEPI score instead.4 (4%)1 (2%)1 (8%)2 (4%)Not sending genomic assay. Using Magee Equations for Estimating Oncotype DX Recurrence Score instead.2 (2%)002 (4%)None of above21 (20%)3 (7%)2 (17%)18 (33%)If using endocrine therapy first, what duration do you plan to use it for the average patient?†Minimum 1 year for all patients0000Minimum 6 months for all patients7 (6%)4 (10%)0 (0%)3 (5%)Minimum 3 months for all patients19 (18%)7 (17%)1 (8%)11 (20%)As short as possible (less than 3 months), until it is safe to proceed with surgery in light of COVID-19 situation57 (53%)14 (34%)9 (75%)34 (62%)Duration of therapy depends on patient''s risk of cancer progression (ie. tumor grade, percent hormone positivity)25 (23%)16 (39%)2 (17%)7 (13%)If using endocrine therapy before surgery, do you plan to re-image the breast prior to surgery?†Yes, re-image all patients27 (25%)14 (34%)1 (8%)12 (22%)No8 (7%)0 (0%)2 (17%)6 (11%)Case by case basis72 (67%)27 (66%)9 (75%)36 (67%)

Citation Format: Ko Un Park, Megan E Gregory, Maryam B Lustberg, Jose G Bazan, Chengli Shen, Shoshana M Rosenberg, Victoria S Blinder, Priyanka Sharma, Lajos Pusztai, Ann H Partridge, Alastair Thompson. Emerging from COVID-19 pandemic: Provider perspective on use of neoadjuvant endocrine therapy (NET) in early stage hormone receptor positive breast cancer [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr SS2-05.

Association of Pre- and Posttreatment Neutrophil-Lymphocyte Ratio With Recurrence and Mortality in Locally Advanced Non-Small Cell Lung Cancer

Objectives

Neutrophil–lymphocyte ratio (NLR) has been associated with mortality in non-small cell lung cancer (NSCLC), but its association with recurrence in locally advanced NSCLC (LA-NSCLC), specifically, is less established. We hypothesized pre- and posttreatment NLR would be associated with recurrence and mortality.

Methods

We studied the association of pretreatment NLR (pre-NLR) and posttreatment NLR at 1 (post-NLR₁) and 3 months (post-NLR₃) with outcomes in patients with LA-NSCLC treated with chemoradiation. Pre-NLR was dichotomized by 5, an a priori cutoff previously shown to be prognostic in LA-NSCLC. Post-NLR₁ and post-NLR₃ were dichotomized by their medians.

Results

We identified 135 patients treated with chemoradiation for LA-NSCLC between 2007 and 2016. Median follow-up for living patients was 61.1 months. On multivariable analysis, pre-NLR ≥ 5 was associated with worse overall survival (HR = 1.82; 95% CI 1.15 – 2.88; p = 0.011), but not with any recurrence, locoregional recurrence, or distant recurrence. Post-NLR₁ ≥ 6.3 was not associated with recurrence or survival. Post-NLR₃ ≥ 6.6 was associated with worse overall survival (HR = 3.27; 95% CI 2.01– 5.31; p < 0.001), any recurrence (HR = 2.50; 95% CI 1.53 – 4.08; p < 0.001), locoregional recurrence (HR = 2.50; 95% CI 1.40 – 4.46; p = 0.002), and distant recurrence (HR = 2.53; 95% CI 1.49 – 4.30; p < 0.001).

Conclusion

Pretreatment NLR is associated with worse overall survival and posttreatment NLR is associated with worse survival and recurrence. These findings should be validated independently and prospectively studied.

Dosimetric parameters associated with radiation-induced esophagitis in breast cancer patients undergoing regional nodal irradiation

BACKGROUND/PURPOSE

Rates of acute esophagitis in breast cancer patients undergoing regional nodal irradiation (RNI) are under-reported. We set to identify esophageal dose-volume constraints associated with grade 2 esophagitis (G2E). We hypothesized that the G2E rate was higher with intensity modulated radiation therapy (IMRT) vs. 3D conformal radiation therapy (3DCRT).

MATERIALS/METHODS

We identified patients that received RNI (50 Gy/25 fractions) from 1/2013 to 6/2019. We retrospectively contoured the esophagus in a consistent manner and recorded esophageal mean dose, max dose, and V10-V50. Our primary endpoint was the G2E rate. Receiver operating characteristics curves analysis (e.g., Youden's J statistic) were used to determine the cutpoints for the dosimetric parameters which were then tested in logistic regression models.

RESULTS

We identified 531 patients (50% left-sided; 41% IMRT; 16.2% G2E). G2E was significantly higher in IMRT vs. 3DCRT patients (23.6% vs. 10.9%, p < 0.0001). All esophageal dosimetric parameters were significantly associated with G2E after adjusting for age and laterality. The cutpoints for esophageal mean dose, V10 and V20 were 11 Gy, 30%, and 15%, respectively. The associations between the dichotomized dose-volume parameters and G2E were OR = 3.82 (95% CI 2.28-6.40, p < 0.0001) for esophageal mean dose, OR = 5.37 (95% CI 3.01-9.58, p < 0.0001) for esophageal V10, and OR = 3.23 (95% CI 1.93-5.41, p < 0.0001) for esophageal V20.

CONCLUSION

In patients receiving RNI with modern techniques, we found that G2E occurs in >15%, and more frequently with IMRT. These data strongly support the routine contouring of the esophagus in RNI planning, and our constraints should be incorporated in future prospective protocols of RNI.

Clinical Effectiveness of an Adaptive Treatment Planning Algorithm for Intensity Modulated Radiation Therapy Versus 3D Conformal Radiation Therapy for Node-Positive Breast Cancer Patients Undergoing Regional Nodal Irradiation/Postmastectomy Radiation Therapy

PURPOSE

Clinical trials support adjuvant regional nodal irradiation (RNI) after breast-conserving surgery or mastectomy for patients with lymph node-positive breast cancer. Advanced treatment planning techniques (eg, intensity modulated radiation therapy [IMRT]) can reduce dose to organs at risk (OARs) in this situation. However, uncertainty persists about when IMRT is clinically indicated (vs 3-dimensional conformal radiation therapy [3DCRT]) for RNI. We hypothesized that an adaptive treatment planning algorithm (TPA) for IMRT adoption would allow OAR constraints for RNI to be met when 3DCRT could not without significantly changing toxicity and locoregional recurrence (LRR) patterns.

METHODS AND MATERIALS

Since 2013, all RNI patients also underwent an adaptive TPA that began with 3DCRT and then changed to IMRT when OAR constraints (mean heart dose ≤500 cGy; ipsilateral lung V20 ≤35%) could not be met. Patients received 2 Gy/d to the prospectively contoured target volumes (including internal mammary nodes). We retrospectively evaluated the dosimetry and clinical outcomes of the treatment groups (IMRT vs 3DCRT). The primary endpoint was the cumulative incidence of LRR as the site of first recurrence, and we specifically address patterns of failure based on dose to the posterior supraclavicular nodal region (SCL-post).

RESULTS

Two hundred forty patients (60% stage III; mean 4.0 + nodes) underwent an adaptive-TPA for RNI after mastectomy (74%) or breast-conserving surgery (26%), resulting in 168 patients treated with 3DCRT and 72 patients treated with IMRT. There were 7 LRRs (2 IMRT, 5 3DCRT) resulting in 4-year LRR of 2.8% for IMRT versus 1.8% for 3DCRT (P = .99). Three patients (2 IMRT, 1 3DCRT) had SCL nodal failures (1 in the SCL-post).

CONCLUSIONS

An adaptive TPA for use of IMRT when 3DCRT does not meet critical OAR constraints resulted in rare high-grade toxicity and no difference in failure patterns between patients treated with IMRT and 3DCRT. These data should provide reassurance that IMRT maintains the therapeutic ratio by preserving cancer control outcomes without excess toxicity when 3DCRT fails to meet OAR constraints.