With pirtobrutinib, time to next treatment often exceeds progression-free survival. This discrepancy exists because disease progression is frequently slow and asymptomatic, meaning clinicians do not need to switch therapies immediately upon seeing radiographic changes, allowing for longer treatment duration.

Traditional endpoints like progression-free survival (PFS) incentivize continuous treatment. The NCI group proposes "treatment-free survival," a novel metric that quantifies time spent *off* therapy. This endpoint better captures the patient experience and rewards treatments that provide durable responses after a finite course.

Real-world data for pemigatinib in cholangiocarcinoma showed a higher response rate (59%) than the pivotal FITE-202 trial (36%). This discrepancy likely stems from the lack of standardized, centrally reviewed imaging in real-world settings, which can inflate perceived response. Comparable progression-free survival across both settings supports this interpretation.

In the adjuvant (post-surgery) setting, Disease-Free Survival (DFS) is a more crucial and patient-relevant endpoint than Progression-Free Survival (PFS) is in the metastatic setting. A DFS event signifies the cancer's return, a major psychological and clinical blow, distinct from the growth of an already-known tumor in the metastatic context.

In metastatic hormone-sensitive prostate cancer (mHSPC), radiographic progression-free survival (rPFS) is no longer seen as a convincing primary endpoint on its own. Clinicians demand a clear signal for overall survival (OS) improvement, citing historical data where early treatment intensification showed significant OS gains.

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.

New imaging criteria declare immediate progression if a patient develops 6 or more new lesions. For 5 or fewer, the old rule requiring a confirmatory scan applies. This change prevents keeping patients on ineffective therapy just to meet trial criteria while preventing premature declarations for minimal changes.

The LEAP-010 trial showed a combination therapy improved tumor response and progression-free survival but failed to improve overall survival, the ultimate measure of benefit. This highlights the risk of relying on surrogate endpoints, which can be misleading, especially when a treatment adds significant toxicity.

The introduction of highly sensitive PSMA PET scans means established endpoints like Metastasis-Free Survival (MFS) may no longer be valid. A metastasis detected by PET likely has a different, better prognosis than one found with older imaging, requiring new validation for this key endpoint.