Stratifying the outcome after neoadjuvant treatment using pathological response classification by the Japanese Breast Cancer Society

Backgrounds Neoadjuvant chemotherapy (NAC) is one of the standard treatment for patients with operable and locally advanced breast cancer. Pathological response after NAC has been assessed according to the Japanese Breast Cancer Society (JBCS) classification in Japan. This classification that was first established in 1998 and revised in 2007 has been used in routine clinical practice in Japan. In the present study, we investigated whether the assessment of pathological response according to this classification could stratify the long-term outcome of patients with breast cancer. Methods Patients with breast cancer who had received neoadjuvant chemotherapy between January 2003 and December 2005 in 6 hospitals participating in this study were identified. Patients whose response was judged to be Grade 2 was reassessed into Grades 2a and 2b according to the updated JBCS classification revised in 2007. Then, the association of pathological response and recurrence-free survival (RFS) was analyzed. Results 635 patients received NAC and 154 relapses (24 %) were observed during a median follow-up of 41.5 months (range 4.2–69.5 months). There was a statistically significant difference in RFS among each pathological response. 5-year RFS of patients with Grade 3 without residual ductal carcinoma in situ was 94 %. 5-year RFS were 88 % in Grade 3, 95 % in Grade 2b, 80 % in Grade 2a, 73 % in Grade 1b, 67 % in Grade 1a, 59 % in Grade 0, respectively. Conclusions An outcome could be stratified by assessing tumor burden following NAC according to the JBCS classification.