Triple-negative breast cancer (TNBC) shows different clinical course from ER-positive cancers. We designed multi-institutional retrospective study to analyze treatment outcomes after post-operative radiotherapy in TNBC.
We retrospectively reviewed 699 TNBC patients with post-operative radiation therapy from 6 institutions between 2008 and 2010. Median age was 49 (range, 24-80) and neoadjuvant chemotherapy was administered in 130 patients (18.6%). Breast conserving surgery was done in 634 (90.7%) and invasive ductal carcinoma was reported in 611 (87.4%). Two hundred and twenty five patients (36.5%) were stage I, 305 (43.6%) in II, and 67 (9.6%) in III. Lymphatic invasion (LI) was reported in 240 patients (34.3%) and extracapsular extension (ECE) was in 49 (7.0%). Patients were irradiated 45-50.4Gy with 25-28 fractions to the breast or chest wall followed by tumor bed boost with 10-16Gy with 5-8 fractions. Simultaneously, additional radiation fields were irradiated to supraclavicular or internal mammary lymph nodal areas. Adjuvant chemotherapy was done in 596 (85.3%).
In median 94 months (range, 7-192) after treatments, 594 patients (85.0%) were no evidence of disease, 31 patients (5.0%) with alive with disease, 3 patients (0.4%) with died due to other causes, and 67 (9.6%) death from the breast cancer. Local recurrence was reported in 33 patients (4.7%), and regional failure was in 31 patients (4.4%), respectively. Distant metastasis was in 78 patients (11.2%). 5-year OS was 91.4%, 5-year LRRFS was 92.3%, 5-year DMFS was 89.4%, 5-year DFS was 85.2%, and 5-year CSS was 91.8%. On univariate analysis, age, clinical/pathologic T stages, clinical/pathologic N stages, histologic grade, LI, and ECE were related to survival rates. On multivariate analysis, younger age (≤50), clinical/pathologic stages, and ECE were also related to the survival outcomes.
We could verify several prognostic factors including age, stage, and ECE related survival outcomes after post-operative radiation therapy in TNBC. Distant metastasis was also more common than loco-regional failures. Further detailed analysis, including more patients scheduled for enrolment, would be necessary.
Jin Hee Kim.
Has not received any funding.
All authors have declared no conflicts of interest.