Benefit of scar boost radiation following postmastectomy radiation in female breast cancer: a retrospective analysis

Abstract

Background: The use of postmastectomy radiation (PMRT) as a standard of care for female breast cancer is well established, with scar boost radiation being a discretionary choice. However, the efficacy of scar boost radiation remains a subject of debate. Methods: A retrospective analysis was conducted from medical records of female patients diagnosed with breast cancer who have undergone PMRT from January 2012 to January 2015 at Srinagarind Hospital, Khon Kaen University. The primary endpoint was chest wall local control (LC), and the secondary endpoints were risk factors associated with chest wall local recurrence (LR), locoregional recurrence (LRR) and overall survival (OS). Results: A total of 549 female patient records were included. The median follow-up time was 21 months. 31.51% of patients received scar boost radiation. The majority of the patients had ductal carcinoma (98.5%) and were histologically graded as grade 2 (44.6%) or 3 (39.0%). The estimated 10-yr chest wall local control rate was 82.14% (95% CI 68.12 - 99.04%) in scar boost group versus 93.18% (95% CI 89.58 - 96.92%) in no scar boost groups. No significant differences between the two groups were found in LR (HR 0.87, 95% CI 0.35-2.19), LRR (HR 1.20, 95% CI 0.60-2.37), and OS (HR 1.05, 95% CI 0.09-11.54). Subset analysis showed that lobular carcinoma was associated with LR and LRR (HR 11.32, 95% CI 3.24-39.54 and HR 5.65, 95% CI 1.71-18.61) while positive supraclavicular node was associated with LRR (HR 4.51, 95% CI 1.37-14.79). Scar boost radiation also resulted in a higher frequency of skin toxicity (grade 1-3), skin fibrosis (grade 1), and radiation pneumonitis (grade 1). Conclusions: There is no evidence supporting that scar boost radiation following PMRT in female breast cancer patients is superior in chest wall LC. Scar boost radiation is also statistically significantly associated with increased toxicity.