Locoregional Recurrence Risk for Postmastectomy Breast Cancer Patients With T1-2 and One to Three Positive Lymph Nodes Receiving Modern Systemic Treatment Without Radiotherapy.

BACKGROUND: Administering postmastectomy radiotherapy (PMRT) to patients with T1-2 breast cancer and one to three positive axillary lymph nodes (ALNs) is controversial. The current study assessed the association of clinicopathologic features and molecular subclassification with locoregional recurrence (LRR) in patients who did not receive PMRT.

METHODS: Between January 2004 and December 2008, 293 patients with T1-2 breast cancer and one to three positive ALNs not receiving PMRT were analyzed. Most of the patients received an anthracycline- or taxane-based regimen or both. The patients were divided according to the four molecular subtypes as follows: luminal A/B, luminal human epidermal growth factor receptor 2 (HER2), HER2, and triple-negative breast cancer. Overall survival (OS) and LRR were calculated using the Kaplan-Meier method, and the clinicopathologic prognostic factors were compared using log-rank tests and the Cox regression model.

RESULTS: After a median follow-up period of 82.8 months, the 10-year LRR and OS were respectively 10 %, and 88.9 %. The patients with triple-negative breast cancer had a higher 5-year LRR rate (10.6 %) than those without this disease (4.2 %) (p = 0.05). Multivariate analysis showed that young age (≤40 years), tumor larger than 3 cm, and the presence of extensive intraductal components were significant risk factors for LRR. The 5-year LRR was 3.1 % for the patients without the aforementioned risk factors, 7.9 % for those with one risk factor, and 25 % for those with two or more risk factors (p < 0.001).

CONCLUSIONS: Administering modern systemic therapy to early breast cancer patients not receiving PMRT reduced the LRR rate. Younger patients, those with a tumor larger than 3 cm, and those with extensive intraductal components might benefit from PMRT.