While neoadjuvant pembrolizumab (KEYNOTE-689) is now standard of care for resectable head and neck cancer, it carries a critical risk. During the pre-surgical treatment window, some patients may experience disease progression or toxicity that makes them ineligible for their planned curative surgery.

In the Keynote 522 trial for early-stage TNBC, adding pembrolizumab to chemotherapy resulted in only a modest improvement in pathological complete response (pCR). Surprisingly, this small initial gain translated into much more robust and significant long-term improvements in event-free and overall survival.

While neoadjuvant-only immunotherapy has a strong rationale, a patient-level cross-trial comparison of CheckMate 816 (neoadjuvant) and 770T (perioperative) suggests the addition of adjuvant therapy improves event-free survival, favoring a full perioperative approach.

Instead of basing adjuvant radiation decisions on a patient's initial, pre-treatment tumor stage, clinicians should use the post-neoadjuvant pathological stage (ypTNM). Patients with a major pathologic response (e.g., downstaging from T3 to T1) may be able to safely avoid additional adjuvant radiation therapy.

In a pivotal neoadjuvant trial of cemiplimab for CSCC, none of the 40 patients who achieved a pathologic complete response (path CR) had relapsed at long-term follow-up. This suggests that path CR can be used as a powerful early indicator of long-term disease control and potential cure.

Retrospective data suggests patients with MSI-high rectal cancer might not just respond poorly to standard neoadjuvant chemoradiation (TNT), but their disease could actually progress. This makes immunotherapy a potentially safer and more effective first-line neoadjuvant choice, not just an alternative.

Data from trials like CheckMate 816 shows that achieving a Pathologic Complete Response (PCR) after neoadjuvant chemo-immunotherapy is a powerful early surrogate endpoint. Patients with PCR demonstrate markedly improved overall and event-free survival.

Unlike immunotherapy, neoadjuvant osimertinib yields poor pathologic complete response (pCR) rates. However, it significantly improves major pathologic response (MPR) and survival, suggesting pCR may be the wrong efficacy endpoint for cytostatic EGFR TKIs, which have a different mechanism of action than immunotherapy.

In a neoadjuvant cemiplimab trial, only 6% of patients had a complete response based on radiographic imaging (RECIST criteria), yet 50% achieved a pathologic complete response. This major discrepancy shows clinicians should not rely solely on scans to assess treatment benefit before surgery.