Data from trials like Niagara suggests a powerful new paradigm for assessing treatment success. Combining urine tumor DNA (uTDNA) for local disease and circulating tumor DNA (ctDNA) for systemic relapse offers a more dynamic view than traditional pathology and is poised to become the superior surrogate endpoint in bladder cancer trials.

Circulating tumor DNA (ctDNA) is a powerful biomarker for identifying high-risk bladder cancer patients. However, its imperfection presents a new clinical dilemma: with a ~12% relapse rate even in ctDNA-negative patients, clinicians must decide whether to withhold adjuvant therapy and accept that risk, or overtreat the 88% who are likely cured.

Upcoming trials like RETAIN and IMVigor011 are using circulating tumor DNA (ctDNA) to guide complex treatment choices in muscle-invasive bladder cancer. This biomarker-driven approach aims to personalize therapy, potentially enabling bladder preservation for some patients and identifying others who need additional adjuvant treatment.

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 adjuvant bladder cancer trials, ctDNA status is both prognostic and predictive. Patients with positive ctDNA after surgery are at high risk of relapse but benefit from immune checkpoint inhibitors. Conversely, ctDNA-negative patients have a lower risk and derive no benefit, making ctDNA a critical tool to avoid unnecessary, toxic therapy.

While circulating tumor DNA (ctDNA) is a powerful prognostic marker, it is not yet part of the formal "clinical complete response" definition for bladder-sparing trials. Experts lack data on its ability to predict the superficial, non-muscle invasive relapses common in this setting.

Current bladder cancer trials often fail to differentiate between patients with primary resistance (never responded) versus acquired resistance (responded, then progressed). Adopting this distinction, common in lung cancer research, could help identify patient subgroups more likely to benefit from immunotherapy re-challenge and refine trial eligibility criteria.

The main barrier to widespread ctDNA use is not its proven ability to predict who will recur (prognostic value). The challenge is the emerging, but not yet definitive, data on its ability to predict a patient's response to a specific therapy (predictive value).

A key lesson in bladder cancer is that patient attrition is rapid between lines of therapy; many who relapse from localized disease never receive effective later-line treatments. This reality provides a strong rationale for moving the most effective therapies, like EV-pembrolizumab, to earlier settings to maximize the number of patients who can benefit.