Prognostic role of adjuvant radiotherapy in triple-negative breast cancer: A historical cohort study.

ABSTRACT

The value of adjuvant radiotherapy in triple-negative breast cancer (TNBC) is currently debated. We assessed the association between adjuvant radiotherapy and survival in a large cohort of Asian women with TNBC. Women diagnosed with TNBC from 2006 to 2011 in five Asian centers (N = 1,138) were included. Survival between patients receiving mastectomy only, breast-conserving therapy (BCT, lumpectomy and adjuvant radiotherapy) and mastectomy with radiotherapy were compared, and adjusted for demography, tumor characteristics and chemotherapy types. Median age at diagnosis was 53 years (range 23-96 years). Median tumor size at diagnosis was 2.5 cm and most patients had lymph node-negative disease. The majority of patients received adjuvant chemotherapy (n = 861, 76%) comprising predominantly anthracycline-based regimes. In 775 women with T1-2, N0-1, M0 TNBCs, 5-year relative survival ratio (RSR) was highest in patients undergoing mastectomy only (94.7%, 95% CI 88.8-98.8%), followed by BCT (90.8%, 95% CI 85.0-94.7%), and mastectomy with radiotherapy (82.3%, 95% CI 73.4-88.1%). The adjusted risks of mortality between the three groups were not significantly different. In 363 patients with T3-4, N2-3, M0 TNBCs, BCT was associated with highest 5-year RSR (94.1%, 95% CI 81.3-99.4%), followed by mastectomy with radiotherapy (62.7%, 95% CI 54.3-70.1%), and mastectomy only (58.6%, 95% CI 43.5-71.6%). Following multivariable adjustment, BCT and mastectomy with radiotherapy remained significantly associated with lower mortality risk compared to mastectomy only. Overall, adjuvant radiotherapy was associated with higher survival in women aged <40 years, but not in older women. Adjuvant radiotherapy appears to be independently associated with a survival gain in locally advanced as well as in very young TNBC.