POSTMASTECTOMY RADIOTHERAPY IN PREMENOPAUSAL VIETNAMESE AND CHINESE WOMEN WITH BREAST CANCER TREATED IN AN ADJUVANT HORMONAL THERAPY STUDY

Abstract Background Adjuvant postmastectomy radiotherapy (RT) decreases the risk of local recurrence of breast cancer and may increase overall survival (OS). Methods and materials After mastectomy, 656 premenopausal Vietnamese and Chinese women with clinical Stage II–IIIA breast cancer, in a clinical trial of adjuvant surgical oophorectomy and tamoxifen, were treated with adjuvant RT according to the availability in the institution. The short-term disease recurrence and OS experience of these 656 women were analyzed using univariate and multivariate methods. Results The 193 patients who did not receive RT differed from the 463 who did in that they had larger tumors and more frequently Grade 3 tumors. With a median follow-up of 3.6 years, in univariate analysis, RT was associated with improved disease-free survival (DFS) (relative risk 0.66; 95% confidence interval 0.49–0.89; p = 0.007) and OS (relative risk 0.71; 95% confidence interval 0.50–1.00; p = 0.051). In multivariate analysis, the relative risk for DFS and OS associated with RT was 0.78 and 0.94, respectively ( p = not significant for both). Kaplan-Meier estimates showed better 5-year DFS (72% vs. 59%; p = 0.006) and OS (78% vs. 70%; p = 0.05) rates with RT. Conclusion In the absence of detailed CT planning capacity, adjuvant RT for premenopausal Vietnamese women was associated statistically with short-term improvement in DFS and OS in univariate, but not multivariate, analysis.