Is pathological response an adequate surrogate marker for survival in neoadjuvant therapy with immune checkpoint inhibitors?

Pathological response (PR) is an oncological outcome measure that indicates the therapeutic response to neoadjuvant therapy. In clinical trials involving neoadjuvant or perioperative interventions, overall survival and disease/event-free survival are typically the primary outcome measures. Although some evidence suggests that pathological complete response (pCR) can serve as a surrogate marker for the primary endpoint in prospective trials, it remains uncertain whether pCR is a true surrogate marker for patients with cancer undergoing curative resection across all solid tumours. Here, we review the role of PR as a surrogate marker and its associated methodological issues in the era of perioperative immune checkpoint inhibitors.