Prognostic significance of residual tumor at the end of NAC. These Kaplan-Meier curves depict that at the end of NAC, patients with complete pathological response (pCR) (blue line in A) had much better OS compared to those with a residual tumor at the end of NAC (green line in A). Surprisingly, patients with ALDH1(−) residual tumors at the end of NAC (purple line in A) also had much better OS. When combined into one group (purple line in B), patients with no residual tumor or ALDH1(−) residual tumor had significantly better OS compared to those with an ALDH1(+) residual tumor at the end of NAC (P = 0.005, HR 10.58, 95% CI 1.65 to 14.68). ALDH1, aldehyde dehydrogenase-1; NAC, neoadjuvant chemotherapy; OS, overall survival.