Pathologic complete response (pCR) after neoadjuvant systemic therapy for localized breast cancer is associated with reduced risk of systemic recurrence.¹ Compared with the traditional approach of empirically testing new agents in the adjuvant setting and waiting years for the results to be available, use of pCR as an intermediate pharmacodynamic biomarker offers the potential to accelerate testing of novel treatment approaches, and improve the probability of success in larger, more definitive trials with disease recurrence end points. Other advantages of aiming for higher pCR rates include the potential for less axillary surgery and higher breast conservation rates. The promise of this approach led the US Food and Drug Administration to accept pCR as an end point supporting accelerated regulatory approval of drugs in this setting.² Randomized clinical trials have shown that systemic therapy has similar effects whether given before surgery as neoadjuvant therapy or after surgery as adjuvant therapy, providing additional support for this approach. Important caveats include the need for achieving large absolute improvements in pCR rates in order to translate into recurrence-free survival gains,³ and that full regulatory approval requires confirmation of improved event-free survival in the same trial showing improved pCR, or a separate confirmatory trial.² This regulatory pathway has generated much interest in testing drugs in the neoadjuvant setting.

局部乳腺癌新辅助全身治疗后的病理完全缓解（pCR）与全身复发风险降低相关。¹与在辅助环境中对新药物进行经验测试并等待数年才能获得结果的传统方法相比，使用 pCR 作为中间药效学生物标志物提供了加速新治疗方法测试的潜力，并提高了成功的可能性具有疾病复发终点的更大、更明确的试验。以更高的 pCR 率为目标的其他优势包括减少腋窝手术的可能性和更高的乳房保留率。这种方法的承诺导致美国食品和药物管理局接受 pCR 作为支持在这种情况下加速监管批准药物的终点。²随机临床试验表明，无论是在手术前作为新辅助治疗还是在手术后作为辅助治疗，全身治疗都具有相似的效果，为这种方法提供了额外的支持。重要的注意事项包括需要在 pCR 率上实现大幅度的绝对改善，以转化为无复发生存期增益，³并且完全监管批准需要在显示 pCR 改善的同一试验中确认改善的无事件生存期，或单独的确认审判。²这种监管途径引起了人们对在新辅助环境中测试药物的极大兴趣。