Clinical outcomes according to molecular subtypes in stage II-III breast cancer patients treated with neoadjuvant chemotherapy followed by surgery and radiotherapy.

Objective: We evaluated the tumor response and clinical outcomes according to molecular subtypes in stage II-III breast cancer patients who received neo-adjuvant chemotherapy (NAC) followed by surgery and radiotherapy.

Methods: We retrospectively analyzed 329 patients with clinical stage II-III breast cancer who received NAC followed by surgery and radiotherapy. Luminal A and B, HER2-enriched and triple-negative subgroups were identified.

Results: The overall pathologic complete response (pCR) rate after NAC was 20.1% and the HER2-enriched subgroup had the highest pCR rate (43.6%), whereas luminal A showed the lowest rate of pCR (4.6%). The median follow-up duration was 55 months (range, 5-98 months). The 5-year overall survival (OS) and disease-free survival (DFS) rates were 88.9% and 72.9%, respectively. In subgroup analysis, according to the pathologic response (pCR vs non-pCR), the triple-negative subtype exhibited a significant difference in 5-year OS rate (100.0% vs 71.6%, P = 0.005) and 5-year DFS rate (93.1% vs 55.1%, P < 0.001). A distinct survival difference according to molecular subtype was found, particularly in the non-pCR group (5-year OS and DFS, P < 0.001, respectively).

Conclusions: The non-pCR group showed significantly decreased 5-year OS and DFS rates compared to the pCR group, especially in triple negative and HER2-enriched breast cancer patients. A significant difference in survival rates and molecular subtypes was found in patients who failed to attain pCR.