Breast Cancer

PV QA 4 - Poster Viewing Q&A 4

TU_6_3376 - Patterns of Care of Adjuvant Radiation Therapy After Lumpectomy and Survival in T1N0M0 Estrogen Receptor Positive Breast Cancer

Tuesday, October 23
2:45 PM - 4:15 PM
Location: Innovation Hub, Exhibit Hall 3

Patterns of Care of Adjuvant Radiation Therapy After Lumpectomy and Survival in T1N0M0 Estrogen Receptor Positive Breast Cancer
A. Lee1, M. Tam2, P. Wu3, N. K. Gerber2, A. J. Lederman1, E. L. Garay4, N. Sheth4, J. Safdieh Jr5, K. N. Choi4, and D. Schreiber6; 1Department of Radiation Oncology, SUNY Downstate Medical Center, Brooklyn, NY, 2Department of Radiation Oncology, NYU Langone Medical Center, New York, NY, 3Department of Radiation Oncology, NYU School of Medicine, New York, NY, 4SUNY Downstate Medical Center, Brooklyn, NY, 5Department of Radiation Oncology, Kings County Hospital Center, Brooklyn, NY, 6Summit Medical Group at MD Anderson Cancer Center, Berkeley Heights, NJ

Purpose/Objective(s): The efficacy of adjuvant radiation following breast conserving surgery for local control and survival are well known. Given the excellent outcomes in early stage breast cancer, there is an increased focus on de-escalation of treatment in patients, particularly those with early stage estrogen receptor (ER) positive breast cancer who receive endocrine therapy. We sought to examine patterns of care of adjuvant radiation therapy (RT) after lumpectomy and outcomes in these most favorable breast cancer patients using the National Cancer Database (NCDB).

Materials/Methods: Patients diagnosed with ER positive pathologic T1N0M0 breast cancer from 2010-2013 who received lumpectomy with negative margins followed by adjuvant radiation and endocrine therapy were identified in the NCDB. External beam radiation therapy dose was limited to 4000-6040cGy and the cohort was further selected to those with Charlson-Deyo comorbidity score of 0. Those with human epidermal growth factor receptor 2 positive status were excluded. Patient- and clinical-related factors were compared between those who received adjuvant RT versus those who did not. Univariable and multivariable logistic regression was performed to assess for predictors of adjuvant RT and boost use. The Kaplan-Meier method was used to assess overall survival (OS) and univariable and multivariable Cox regression analysis was used to assess impact of covariables on OS.

Results: There were 39,199 patients who met the study criteria, of which 21,312 (54.4%) received adjuvant RT and 18,887 (45.6%) did not. Median follow-up for living patients was 48.4 months (IQR 37-61) and 71.2% of patients who received adjuvant RT received a boost. Five-year OS for those who did and did not receive RT was 96.3% and 92.9%, respectively (p<0.001). Among those who received RT, 5-year OS was 96.7% for those who received a boost versus 95.2% for those who received no boost (p=0.001). On multivariable survival analysis, older age (HR 1.96-4.85, p<0.001) and 10-20mm (T1c) tumor size (HR 1.55, 95% CI 1.20-2.00, p=0.001) were associated with worse survival. Treatment at an academic facility (HR 0.90, 95% CI 0.67-1.21, p<0.001) and receipt of postop RT (HR 0.66, 95% CI 0.55-0.79, p<0.001) were associated with improved survival. Race, grade and receipt of boost were not associated with any differences in survival. When stratifying by age group, there was still a survival benefit in all groups with postop RT, including among those over 70 years (log-rank p<0.001).

Conclusion: Nearly half of patients with T1N0M0 ER-positive breast cancer did not receive post-lumpectomy radiation therapy though it was associated with a survival benefit, even among elderly patients.

Author Disclosure: A. Lee: None. P. Wu: None. N.K. Gerber: None. A.J. Lederman: None. E.L. Garay: None. N. Sheth: None. K.N. Choi: None. D. Schreiber: None.

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