Clinicopathological predictors of distant recurrence in breast cancer patients achieving pathological complete response after neoadjuvant chemotherapy.

BACKGROUND: Pathological complete response (pCR) after neoadjuvant chemotherapy (NAC) is associated with favorable prognosis in breast cancer; however, a subset of patients still experience distant recurrence. Data on long-term outcomes and predictors of recurrence after pCR remain limited.

METHOD: This retrospective observational study was conducted as an extended follow-up analysis of a previously reported multicenter cohort. We included 365 patients with primary breast cancer who achieved pCR after NAC at four institutions between 2007 and 2016. Distant metastasis-free survival (DMFS) was the primary endpoint. Survival outcomes were estimated using the Kaplan-Meier method, and univariate Cox proportional hazards models were used to identify factors associated with distant metastasis.

RESULTS: With a median follow-up of 96 months, distant metastasis developed in 20 patients (5.5%). The 10-year DMFS and overall survival rates were 94.6% and 95.2%, respectively. Distant metastasis was most frequently observed in the pure HER2 subtype, although differences among subtypes were not statistically significant. The brain was the most common site of distant metastasis and was observed across all subtypes. In univariate analysis, pretreatment clinical lymph node involvement was significantly associated with distant metastasis.

CONCLUSION: Long-term outcomes after achieving pCR were generally favorable but pretreatment clinical lymph node involvement remained a risk factor for distant metastasis. Brain metastases were observed across breast cancer subtype, suggesting that this recurrence pattern should be considered during long-term follow-up of patients achieving pCR after NAC.