Loco-regional recurrence rates and prognostic factors for failure in node-negative patients treated with mastectomy alone: implications for postmastectomy radiation

Abstract

Purpose/Objective: Randomized trials have shown that post-mastectomy radiation therapy (PMRT) reduces loco-regional recurrence (LRR) of breast cancer by approximately two-thirds. Survival appears to be improved in patients who are at higher risk of LRR. This study addresses whether there are any subsets of patients with node-negative breast cancer, treated by mastectomy alone, who have a sufficiently high risk of local-regional recurrence that PMRT might be of benefit. Materials/Methods: A retrospective analysis of a cohort of 281 women who were treated at Massachusetts General Hospital with mastectomy and who were found to have no involved lymph nodes after axillary dissection. None of the patients received PMRT or adjuvant systemic treatment. The rates of isolated LRR (LRR as the first event, without evidence of distant metastases for at least four months after the date of LRR) and total LRR (LRR with or without distant metastases) were calculated using Kaplan-Meier analysis, and a number of histologic characteristics were examined as potential prognostic factors. Median follow-up was 12 years. Results: The proportion of isolated LRR in the entired cohort was 16/281, while total LRR was 20/281. At 12 years, the actuarial rate of isolated LRR was 6.6% and the actuarial rate of total LRR was 8.4% in the entire node-negative cohort. The chest wall was the site of failure in 89%. Margin status (p=0.009) and size (p=0.04) were found to be significant predictors of LRR. Actuarial isolated LRR at 12 years was 15.9% in patients with tumors >3 cm in size. When T3 tumors were excluded, actuarial isolated LRR at 12 years was 22.8% in the subset of patients with tumors between 3 and 5 cm in size. Actuarial isolated LRR at 12 years was 39.4% in patients with close margins (less than 2 mm). Conclusions: Adjuvant radiation therapy has not been routinely recommended for node-negative patients after mastectomy, except for T3 tumors, because the rate of LRR has been low in that population as a whole. This study suggests, however, that node-negative patients with tumors 3–5 cm in size, as well as those who have close margins of resection, have a significantly high risk of LRR. These individuals may possibly benefit from PMRT. Because the chest wall is by far the most common site of failure, it is reasonable to consider treating the chest wall alone, without regional lymph nodes, in these patients and thereby minimize the side effects of PMRT.