Treatment efficacy score: a better surrogate for arm-level survival differences in neoadjuvant breast cancer trials?

Neoadjuvant chemotherapy is widely used in the therapy of stage II-III breast cancers and pathologic complete response (pCR; ypT0/is, ypN0) predicts excellent long-term survival. However, the correlation between improvement in pCR rate and survival is highly variable across trials. A major limitation of pCR is that it does not capture downstaging in patients with residual disease. We previously introduced the residual cancer burden (RCB) score that measures pathologic response on a continuous scale. Comparison of RCB score distributions between trial arms reflects treatment efficacy more accurately than differences in pCR rate. We developed the treatment efficacy score (TES) as a new statistical metric that appears to be a better surrogate for trial arm-level survival improvement than pCR rate difference.