The influence of histologic grade on outcomes of elderly women with early stage breast cancer treated with breast conserving surgery with or without radiotherapy

Abstract Purpose/Objective(s) Two large randomized trials, CALGB 9343 and PRIME II, support omission of radiotherapy after breast conserving surgery (BCS) in elderly women with favorable-risk early stage breast cancer intending to take endocrine therapy. However, patients with grade 3 (G3) histology were underrepresented on these trials. We hypothesized that high-grade disease may be unsuitable for treatment de-escalation and report the oncologic outcomes for elderly women with favorable early stage breast cancer treated with BCS with or without radiotherapy. Materials/Methods The Surveillance, Epidemiology and End Results (SEER) database was queried for women between 70-79 years of age with invasive ductal carcinoma (IDC) diagnosed between 1998 and 2007. This cohort was narrowed to women with T1mic-T1c, N0, ER+ IDC treated with BCS with or without external beam radiation (EBRT). The primary endpoints were 5- and 10-year cause-specific survival (CSS). Univariate and multivariate analyses were performed. Propensity-score matching (PSM) of T-stage, year of diagnosis, and age was utilized to reduce selection bias while comparing treatment arms within the G3 subgroup. Results 12,036 women met inclusion criteria with a median follow-up was 9.4 years. EBRT was omitted in 22% of patients, including 21% with G3 disease. Patients in the EBRT cohort were slightly younger (median 74 vs. 75 yrs, p Conclusion In this database analysis, omission of radiotherapy after BCS in elderly women with favorable-risk, early stage, grade 3 breast cancer was associated with inferior CSS. Further prospective data in this patient population are needed to confirm our findings and conclusions.