While depth of response strongly predicts survival for an individual patient, the FDA analysis concludes it cannot yet be used as a surrogate endpoint to replace overall survival in pivotal clinical trials. It serves as a measure of drug activity, similar to response rate, but is not sufficient for drug approval on its own.

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Despite the ASCENT-07 trial failing its primary progression-free survival (PFS) endpoint, an early overall survival (OS) signal emerged. This divergence suggests the drug may confer a survival advantage not captured by the initial endpoint, complicating the definition of a "negative" trial and warranting further follow-up.

The confirmatory Code Break 200 study for sotorasib demonstrated a statistically significant improvement in progression-free survival (PFS) over docetaxel. However, it failed to show a similar benefit in overall survival (OS), a critical distinction for oncologists weighing long-term patient outcomes.

In trials like ASCENT-4, where over 80% of the control arm received sacituzumab govitecan upon progression, the true overall survival (OS) benefit is obscured. This makes progression-free survival (PFS) a more reliable endpoint for evaluating the drug's first-line efficacy.

The FDA issued guidance supporting minimal residual disease (MRD) as an approval endpoint in multiple myeloma. This directly contradicts the CBER division’s recent rejections of drugs based on single-arm response rates, creating a "schizophrenic" and unpredictable regulatory landscape for developers.

The FDA's critique of both CREST and Potomac trials highlights that while event-free survival (EFS) endpoints were met, the lack of improvement in overall survival or prevention of muscle-invasive disease makes the risk/benefit profile questionable for an early-stage cancer, where treatment-related harm is a primary concern.

In neoadjuvant therapy, a patient's long-term outcome is better predicted by stopping tumor DNA shedding (ctDNA clearance) than by achieving pathologic complete response (pCR), the traditional gold standard. This redefines what constitutes a successful treatment response before surgery.

A pooled FDA analysis of four major kidney cancer trials found no "magic number" or threshold for tumor shrinkage that guarantees a favorable outcome. Instead, the relationship is linear: any incremental increase in tumor reduction correlates with better 36-month overall 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.

The GLORA-IV trial is designed with a dual endpoint, evaluating both patient response rate and overall survival. This structure creates an alternative pathway for regulatory approval based on response rates, which can be assessed faster than survival, strategically de-risking the lengthy and expensive trial process.

Immunotherapies can be effective even without causing significant tumor shrinkage. Immunocore's drug KimTrack had a low 5-7% objective response rate (ORR) but demonstrated a massive overall survival (OS) benefit, challenging the reliance on traditional chemotherapy metrics for evaluating modern cancer treatments.