Locoregional control of downstaged breast-conserving surgery after neoadjuvant chemotherapy: A propensity-matched study in Chinese patients.

This study aimed to evaluate the locoregional recurrence-free survival (LRFS) associated with breast-conserving surgery (BCS) based on the regressed tumor extent after neoadjuvant chemotherapy (NAC) (neoadjuvant group) versus upfront BCS without NAC (adjuvant group) in nonmetastatic Chinese patients. Two approaches of 1:1 propensity score matching (PSM), pre-NAC and post-NAC baseline matching, were employed. In the pre-NAC baseline matching, clinicopathological features prior to NAC in the neoadjuvant group were matched with corresponding features in the adjuvant group; whereas in the post-NAC baseline matching, the features after NAC in the neoadjuvant group were matched with those in the adjuvant group. Baseline characteristics were well balanced between groups after matching, with a median follow-up duration of 50.8 months. In the pre-NAC baseline matching, a total of 553 case pairs were matched. The 5-year LRFSs did not significantly differ between neoadjuvant and adjuvant groups (94.37% vs 93.85%, P > 0.05), nor did the 8-year LRFSs (91.80% vs 92.08%, P > 0.05). In the post-NAC baseline matching, 645 case pairs were included. Again, no statistically significant differences were observed in the 5-year (94.78% vs. 92.44%, P > 0.05) and 8-year LRFS (91.26% vs. 89.67%, P > 0.05) between the two groups. Subgroup analyses stratified by RECIST response and tumor shrinkage extent likewise demonstrated no significant difference in both approaches. These findings indicate that, under contemporary treatment regimens and surgical standards, post-NAC BCS based on the regressed tumor extent did not increase the risk of locoregional recurrence in Chinese patients.