Contrary to concerns about tolerating Enfortumab Vedotin (EV) after major surgery, 80% of muscle-invasive bladder cancer patients who began the adjuvant phase in the KEYNOTE B15 trial successfully completed it. This suggests the regimen is more manageable post-cystectomy than anticipated.
While promising, current ctDNA technology is not robust enough to justify stopping effective neoadjuvant systemic therapy in bladder cancer, even if a patient becomes ctDNA negative. Experts argue against using it to de-escalate treatment outside of a clinical trial due to the risk of undertreating a lethal disease.
Giving EV Pembro perioperatively for muscle-invasive bladder cancer provides the best chance for a cure. Waiting to use it in the first-line metastatic setting is a major gamble, as many patients relapse and may not get a second chance at effective therapy. The consensus is to use the best treatment upfront.
The 6% two-year landmark OS benefit for EV Pembro in the B15 trial appears modest compared to other EV Pembro studies. However, this is due to comparing it against an active, effective control (GEM-CIS chemotherapy), unlike trials that used surgery alone, reinforcing the value of neoadjuvant therapy overall.
While smaller trials like KEYNOTE-905 can show dramatic results, they are subject to more statistical noise. Larger, thousand-patient studies like B15 and Niagara, with narrower confidence intervals, are considered closer to the true effect size and provide a more stable foundation for establishing the standard of care.
While both the B15 (EV Pembro) and Niagara (Gem-Cis-Durvalumab) trials were positive, B15 demonstrated a significantly higher pathologic complete response rate (56% vs 37%) and more favorable hazard ratios for survival endpoints. This suggests EV Pembro is the "more positive" regimen and likely the preferred standard of care.
Despite the perception that cisplatin-ineligible patients have worse disease biology, the pathologic complete response rates to neoadjuvant EV Pembro were nearly identical (56-57%) in both cis-ineligible (KEYNOTE-905) and cis-eligible (KEYNOTE-B15) trials. This suggests the regimen's high efficacy may overcome underlying biological differences.