A real-world study found that 25% of patients on pemigatinib had extrahepatic cholangiocarcinoma, a subtype where the drug's FGFR2 fusion target is historically rare. This significant deviation from established biology suggests potential issues with physician-abstracted data, such as mislabeling or referral bias, highlighting the need for cautious interpretation of real-world patient cohorts.

The trial's 57.1% pathologic complete response (pCR) rate is deceptively conservative. It categorized patients who responded well but declined surgery as non-responders, suggesting the treatment's true biological efficacy is even higher than the already impressive reported figure.

In the SUNRISE 2 trial, 44% of patients had no detectable tumor after pre-treatment resection. This high baseline inflates the final clinical complete response (CR) rates (e.g., 59% in the control arm), making CR a misleading indicator of the actual therapeutic benefit, which was a much smaller improvement over baseline.

In the ASCENT-07 trial, investigators may have prematurely switched patients from the standard chemotherapy arm to superior, commercially available ADCs at the first hint of progression. This real-world practice can mask an experimental drug's true benefit on progression-free survival.

A real-world analysis of pemigatinib reported low rates of dose reduction or discontinuation. This may be misleading, as the toxicities of FGFR inhibitors (e.g., nail, skin, eye issues) are cumulative and worsen over extended periods. The study's shorter follow-up likely didn't capture the full long-term safety profile of the drug.

Contrary to typical findings where real-world data underperforms, liso-cel CAR T-cell therapy in CLL demonstrates significantly better outcomes in practice than in its approval trial (over 80% response rate vs. under 50%). This suggests that using the therapy earlier in healthier, less-refractory patients unlocks its true potential.

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.

Experts believe the stark difference in complete response rates (5% vs 30%) between two major ADC trials is likely due to "noise"—variations in patient populations (e.g., more upper tract disease) and stricter central review criteria, rather than a fundamental difference in the therapies' effectiveness.

The study's progression-free survival (PFS) curve was unusually smooth, lacking the stepwise drops expected from scheduled scans in oncology trials. More alarmingly, the "numbers at risk" table showed more patients remaining than were represented on the graph at certain time points—a statistical impossibility suggesting a significant reporting or programming error.