Abstract
The primary objective of our study was to estimate the difference in locoregional recurrence-free survival (LRFS) and investigate the influence of various clinical factors on the risk of locoregional recurrence (LRR) in post-mastectomy breast cancer patients treated with two different radiation fractionations. Data from 317 post-mastectomy patients were retrospectively analyzed. The conventional fractionation schedule was 50 Gy in 25 fractions; the hypofractionated schedule was 42.6 Gy in 16 fractions. LRFS between the two fractionations was estimated and compared. The median LRFS for hypofractionated radiation (n = 194) is 52.5 months (95% CI 23.0-60.0); for conventional fractionated radiation (n = 123) is 60.0 months (95% CI 35.5-60.0; p = 0.008), significant difference at first, but not after further analysis. With univariate cause-specific risk analysis, the hazard ratio (HR) for recurrence with hypofractionated radiation was 1.55 (95% CI 0.76-3.15; p = 0.2). The cause-specific HR for competing events with hypofractionated radiation was 1.04 (95% CI 0.67-1.60; p = 0.9). With multivariable cause-specific hazard analysis, HR for recurrence with hypofractionated radiation vs. conventional is 1.27 (95% CI 0.61-2.65; p = 0.5). Nodal stage is a significant predictor of LRR. Positive margins are associated with higher LRR risk (HR 2.02; p = 0.052). Age, tumor stage, chemotherapy, histology, tumor grade, and hormone receptor status did not significantly influence LRR risk. For post-mastectomy breast cancer patients, hypofractionated radiation treatment is not different from conventional fractionation in achieving locoregional control. Lymph node positivity is a crucial determinant of local recurrence.