2941 - Evaluating the Role of Postoperative Radiation in Low-Risk, Early-Stage Breast Cancer Stratified by Oncotype DX Recurrence Score: A National Cancer Database Analysis
Presenter(s)
J. Gurewitz1, A. Shah1, C. Hardy Abeloos1, J. G. Bazan Jr2, N. K. Gerber3, and P. Wu2; 1Department of Radiation Oncology, NYU Langone Health, New York, NY, 2Department of Radiation Oncology, City of Hope National Medical Center, Duarte, CA, 3Department of Radiation Oncology, NYU Grossman School of Medicine, New York, NY
Purpose/Objective(s): The DEBRA Trial is evaluating whether an Oncotype =18 is an effective biomarker to identify patients with low risk, early-stage breast cancer, receiving adjuvant endocrine therapy, who can safely omit postoperative radiation therapy (RT). We use the National Cancer Database (NCDB) to assess the impact of RT on overall survival (OS) in women who are DEBRA-eligible (Oncotype =18) compared to those who are ineligible (Oncotype >18).
Materials/Methods: We began with 4,231,162 patients with invasive breast cancer. There were 92,594 patients analyzed after filtering for females, aged 50-69, tumor size =2cm, node negative, ER + or PR +, HER2-, lumpectomy with negative margins, adjuvant hormone therapy, no chemotherapy, complete data and known oncotype score. Of these, 69,412 (75%) had Oncotype =18 (DEBRA-eligible), and 23,182 had Oncotype >18 (non-DEBRA). We examined receipt of postoperative RT (vs no RT) and performed logistic regression to identify predictors of RT omission. Multivariable Cox proportional hazards models evaluated overall survival (OS).
Results: In the entire cohort, median age was 61 years, 83% of patients were white, 62% of tumors were 1 cm – 2 cm in greatest dimension, 91% had low or intermediate grade disease, 79% had ductal histology, and 5% had lymphovascular invasion (LVI). Among the 69,412 patients with an Oncotype =18, 67,265 (97%) received RT and 2,147 (3%) did not. Among the 23,182 patients with an Oncotype >18, 22,541 (97%) received RT and 641 (3%) did not. The median follow-up was 64.7 and 64.8 months in the Oncotype =18 and >18 cohorts, respectively. In the DEBRA-eligible cohort, omission of radiation was associated with worse survival (adjusted HR 1.87, CI 1.56 – 2.25, p<0.001). The 5-year OS with and without RT were 97.9% and 94.8% respectively. The 7-year OS with and without RT were 96.2% and 92.4%, respectively. In the non-DEBRA cohort, omission of RT was associated with worse survival (adjusted HR 2.01, CI 1.52 – 2.67, p<0.001). The 5-year OS with and without RT were 97.4% and 93.0%, respectively. The 7-year OS with and without RT were 95.2% and 88.3%, respectively. In both cohorts, worse survival was also associated with age 60-70 (vs. 50-60), T1c (vs. T1mi-T1b), high grade, black ethnoracial category (vs. white), Charlson Deyo Comorbidity Index >0, lower educational attainment, and treatment at community cancer program (vs. academic/research program) (p<0.001). In the non-DEBRA cohort, the presence of LVI was also associated with worse survival (p=0.020).
Conclusion: Postoperative RT was associated with a significant improvement in OS across all Oncotype DX groups, though the absolute survival benefit from RT was smaller in the Oncotype =18 cohort. These findings reinforce the need to complete accrual to randomized trials such as DEBRA to identify biomarkers that best select patients who may not benefit from adjuvant RT.