Pathological Complete Response and Accelerated Drug Approval in Early Breast Cancer

Neoadjuvant trials introduce new drugs preoperatively in patients with localized breast cancer, using the rate of pathological complete response as the primary end point. The FDA has issued guidance for using this end point in applying for accelerated drug approval. New drugs for breast cancer have historically been approved first for patients with metastatic disease who have few remaining options for systemic treatment. Approval for an adjuvant indication occurs years later, after large, randomized trials with prolonged follow-up have been conducted in patients with early-stage disease. Recently, neoadjuvant trials have introduced new drugs preoperatively in patients with localized breast cancer. Such treatment aims to render locally advanced cancers operable, facilitate breast-conserving surgery, and ultimately improve survival. The rate of pathological complete response — absence of residual invasive cancer on pathological evaluation of resected breast specimens and lymph nodes after preoperative . . .