Purpose: To assess patterns of locoregional failure (LRF) in lymph node-positive (LN+) breast cancer patients treated with mastectomy and adjuvant chemotherapy (+/- tamoxifen) and without postmastectomy radiotherapy (PMRT) in five National Surgical Adjuvant Breast and Bowel Project trials.
Patients and methods: We examined 5,758 patients enrolled onto the B-15, B-16, B-18, B-22, and B-25 trials. Median follow-up time was 11.1 years. Distribution of pathologic tumor size was < or = 2 cm, 2.1 to 5 cm, and more than 5 cm in 30%, 52%, and 11% of patients, respectively. Distribution of the number of LN+ was one to three, four to nine, and > or = 10 in 51%, 32%, and 16% of patients, respectively. Ninety percent of patients received doxorubicin-based chemotherapy.
Results: The overall 10-year cumulative incidences of isolated LRF, LRF with or without distant failure (DF), and DF alone as first event were 12.2%, 19.8%, and 43.3%, respectively. Cumulative incidences for LRF as first event with or without DF for patients with one to three, four to nine, and > or = 10 LN+ were 13.0%, 24.4%, and 31.9%, respectively (P < .0001). For patients with a tumor size of < or = 2 cm, 2.1 to 5.0 cm, and more than 5.0 cm, these incidences were 14.9%, 21.3%, and 24.6%, respectively (P < .0001). Multivariate analysis showed age, tumor size, premenopausal status, number of LN+, and number of dissected LN as significant predictors for LRF as first event.
Conclusion: In patients with large tumors and four or more LN+, LRF as first event remains a significant problem. Although PMRT is currently recommended for patients with four or more LN+, it may also have value in selected patients with one to three LN+. However, in the absence of a randomized trial examining the worth of radiotherapy in this group of patients, the value of PMRT remains unknown.