Impact of Breast Cancer Molecular Subtypes on Locoregional Recurrence in Patients Treated with Neoadjuvant Chemotherapy for Locally Advanced Breast Cancer

Background: Gene expression studies have identified distinct breast cancer subtypes, including luminal A, luminal B, Her2-enriched, and Basal-like, which differ in survival. The impact of subtypes on locoregional recurrence (LRR) after neoadjuvant chemotherapy for locally advanced breast cancer is unknown.

Methods: A total of 149 patients with stage II and III breast cancer with known ER, PR, and HER2 who underwent neoadjuvant chemotherapy from 1991 to 2005 were analyzed. We used clinical assays to distinguish luminal A (ER or PR+/HER2-, n = 55), luminal B (ER or PR+/HER2+, n = 25), HER2 (ER and PR-/HER2+, n = 20), and Basal-like (ER, PR, and HER2-, n = 49) subtypes. Covariates associated with LRR were evaluated by logistic regression and differences between subtypes tested using Wald χ(2).

Results: Median follow-up was 55 months. Forty-nine (33%) patients had breast conservation (BCT) with radiation, 82 (55%) had a mastectomy with radiation, and 18 (12%) had a mastectomy alone. Eighty-eight (59%) were clinically node positive. A pathologic complete response was seen in 39 (26%) patients. LRR was identified in 11 (7%) patients: 2 after BCT (4%) and 9 after mastectomy (9%). LRR rates by subtype are as follows: luminal A 2 of 55 (4%), luminal B 1 of 25 (4%), Her2 1 of 20 (5%), and basal-like 7 of 49 (14%). Compared with all other subtypes, basal-like patients were more likely to have a LRR (7/49 (14%) vs. 4/100 (4%), p = 0.03).

Conclusions: Molecular subtype predicts LRR with basal-like patients more likely to develop LRR. These patients may be candidates for investigation with novel chemotherapy regimens and radiation sensitizing agents, which may offer improvement in local control.