Residual Cancer Burden Class Associated with Survival Outcomes in Women with Different Phenotypic Subtypes of Breast Cancer After Neoadjuvant Chemotherapy

The residual cancer burden class informs survival outcomes after neoadjuvant chemotherapy. We evaluated the prognostic ability of the RCB for survival outcomes in women with different phenotypic subtypes of breast cancer treated with neoadjuvant chemotherapy. Additional variables were assessed for inclusion with the RCB to further improve the model's discriminative ability.We conducted a retrospective review of patients completing at least 75% of the recommended cycles of neoadjuvant chemotherapy between 1 January 2010 and 31 December 2016. Phenotypic subtypes were defined by hormone receptor and human epidermal growth factor receptor 2 (HER2) status at diagnosis, classified as HR+/HER2-, HER2+, or triple-negative breast cancer (TNBC). The RCB class was calculated and survival endpoints of overall survival, recurrence-free survival, and distant recurrence-free survival were analyzed using Kaplan-Meier and Cox proportional hazards methods. The discriminative ability of the models was quantified by Harrell's C-index.Overall, 532 women met the inclusion criteria. Median follow-up was 65 months. In univariate models, RCB was significantly associated with OS, RFS, and DRFS. The RCB class had good discriminative ability for OS, RFS, and DRFS survival, with Harrell's C-indices of 0.68, 0.67, and 0.68, respectively. The RCB class discriminated well for each survival endpoint within HER2+ and TNBC, but did not discriminate well for HR+/HER2- (OS Harrell's C-indices of 0.77, 0.75, and 0.52, respectively).The RCB class was prognostic for OS, RFS, and DRFS after neoadjuvant chemotherapy, but prognostic discrimination between patients with subtype HR+/HER2- was not observed during the follow-up period for which the overall event rate was low.