Comparison of survival effects between using electron and modulated X-ray beams for boosting irradiation in breast cancer patients after breast-conserving surgery and postoperative radiotherapy

Objective To compare the survival effects between using electron beams (EB) and modulated X-ray beams (XB) for boosting irradiation in breast cancer patients after breast-conserving surgery and postoperative radiotherapy. Methods This study retrospectively included 485 breast cancer patients who underwent breast-conserving surgery at Beijing Cancer Hospital. All patients underwent either EB or XB for tumor bed boost irradiation (10-16 Gy/5-8 fractions) after whole-breast irradiation of 46-50 Gy/23-25 fractions. Results Median follow-up time for the cohort was 96.04 months. Statistically significant increase of local recurrence free Survival (LRFS) was observed in XB group than in EB group. The 5-year and 10-year LRFS was both 98.4% in XB group, as well as 94.2% and 93.2% in EB group, respectively (χ2=4.190, P 0.05). The multivariate analysis showed that LRFS was significantly correlated with age≤40, positive pathological lymph nodes and positive expression of Her-2 receptor. But boost irradiation method was not independent prognostic factor for LRFS and OS (P>0.05). Conclusions For cancer patients treated with breast-conserving surgery and whole-breast postoperative radiation followed by a boost irradiation to tumor bed, XB irradiation was superior to EB irradiation in term of LRFS, yet no difference of OS was observed in both groups. Key words: Breast cancer; Breast-conserving surgery; Postoperative irradiation; Tumor bed boost