Pathologic method for extracting good prognosis group in triple‐negative breast cancer after neoadjuvant chemotherapy

The area of residual tumor (ART) is a prognostic factor in patients treated with neoadjuvant chemotherapy (NAC) for lung, pancreatic, and rectal cancers. This study aimed to evaluate the usefulness of ART as a method for predicting the prognosis of triple‐negative breast cancer (TNBC) patients after NAC. We included 143 patients with TNBC treated with NAC. The ART at the maximum cut surface of the residual tumor was measured. We divided the patients into three groups: ART‐0 (ART = 0 mm(2)), ART‐low (0 mm(2) < ART ≤ 136mm(2)), and ART‐high (ART > 136 mm(2)), and compared their clinicopathologic factors and prognosis. There were no significant differences in either recurrence‐free survival (RFS) or overall survival (OS) between ART‐0 and ART‐low; however, the ART‐high group had significantly shorter RFS and OS than the ART‐0 and ART‐low groups. Multivariate analysis showed that ART‐0 and ‐low and ypN(−) were independent favorable prognostic factors for RFS. Groups with both ART‐low and ypN(−) as well as those with ART‐0 and ypN(−) showed significantly longer OS and RFS than the other groups (P < .05). Moreover, there was no significant difference in the RFS and OS between the ART‐0 and ypN(−) groups and the ART‐low and ypN(−) groups (P = .249 and P = .554, respectively). We concluded that ART is a candidate histopathological evaluation method for predicting the prognosis of TNBC patients treated with NAC. Furthermore, postoperative chemotherapy could be omitted in patients with ART‐0 and ypN(−) (pathological complete response) and those with ART‐low and ypN(−).