Breast Cancer

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TU_8_3394 - The Impact of Adjuvant Radiation Therapy in Elderly Patients with ER Positive, Early Stage Breast Cancer

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

The Impact of Adjuvant Radiation Therapy in Elderly Patients with ER Positive, Early Stage Breast Cancer
G. Q. Yang1, A. O. Naghavi2, A. G. B. Orman2, R. Diaz2, and K. A. Ahmed2; 1H. Lee Moffitt Cancer Center and Research Institute, Department of Radiation Oncology, Tampa, FL, 2H. Lee Moffitt Cancer Center and Research Institute, Tampa, FL

Purpose/Objective(s): Adjuvant radiotherapy (RT) following breast-conservation surgery (BCS) in elderly (≥ 70 years) patients with early stage breast cancer has been demonstrated to decrease rates of ipsilateral breast recurrence (IBTR) in prospective randomized trials. The results of these trials which were not powered to detect overall survival have influenced practice guidelines, and suggest that adjuvant RT may be omitted in well-selected, early stage breast cancer patients who are hormone receptor positive. We hypothesize that with a sufficiently powered cohort, adjuvant RT may have an impact on overall survival.

Materials/Methods: The National Cancer Data Base (NCDB) was queried for patients ≥70 years of age with pathologic T1 N0, clinical M0, ER+/PR+/Her2- breast cancers from 2010-2015. All patients underwent BCS with negative surgical margins, were reported to have started hormonal therapy, and survived greater than 3 months post-operatively. Patients with Charlson-Deyo comorbidity index (CDCI) greater than 1 were excluded, as were patients that received any chemotherapy. Predictors of overall survival were analyzed using the Kaplan-Meier technique and Cox proportional hazard analysis, and a 2-sided p-value of <0.05 was considered significant.

Results: A total of 22,510 patients matching the inclusion criteria were identified, and median follow-up was 39 months (interquartile range 27-55 months). There were 7504 patients (33%) with BCS alone compared to 15,006 (67%) with BCS+RT. Patients with BCS alone had mean KM estimated survival of 74 months compared to 80 months for patients with BCS+RT (log-rank p<0.01). KM Survival analysis of patients 70-75 years old with CDCI of 0 demonstrated 3 year and 5 year actuarial OS of 96% and 90% respectively for BCS alone (n=2165), compared to patients with BCS+RT (n=7592) with 3 year and 5 year actuarial OS of 98% and 95% respectively (log-rank p<0.01). Accounting for patient age, CDSI, grade of disease, income level, and race, addition of RT was significantly associated with improved OS on multivariate analysis (HR 0.72 95%CI 0.65-0.80, p<0.001). Other variables significantly impacting OS on MVA were increasing age (HR 1.1 95%CI 1.1-1.1, p<0.001), increased CDSI (HR 1.7 95% CI 1.5-1.8, p<0.001), and moderately differentiated grade (HR 1.1 95% 1.0-1.23, p=0.04).

Conclusion: This large scale, population based analysis of elderly, well-selected early stage breast cancer patients with favorable hormonal receptor profile demonstrates a significant impact of adjuvant RT on overall survival. These findings suggest that for the patients with few comorbidities and long life expectancy, adjuvant RT may be of potential benefit.

Author Disclosure: G.Q. Yang: None. A.O. Naghavi: None. A.G. Orman: None. R. Diaz: Travel Expenses; AACR. Member, Advisory Council; Global Health Outreach.

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