The prognostic value of a positive ctDNA test in urothelial cancer intensifies throughout the treatment journey. Failure to clear ctDNA after neoadjuvant therapy and then surgery is associated with a dramatically increasing hazard ratio for death, signaling profound treatment failure.
A positive ctDNA result post-surgery in an immunotherapy-naive patient warrants starting treatment. Conversely, if a patient received neoadjuvant immunotherapy and remains ctDNA positive after surgery, it signals resistance, making continuation of the same therapy illogical and creating a clinical paradox.
Beyond a simple positive/negative result, the quantitative level of ctDNA is highly prognostic in bladder cancer. Similar to PSA in prostate cancer, higher ctDNA levels correlate with a significantly worse prognosis, offering a more nuanced risk assessment tool than a binary test.
The type of treatment inducing ctDNA clearance matters. Clearance from immunotherapy appears to be more permanent and strongly prognostic than clearance from chemotherapy, which can be transient. This suggests immunotherapy may achieve a more profound and lasting elimination of cancer cells versus cytotoxic agents.
Contrary to assumption, persistent ctDNA after neoadjuvant therapy does not always mean incurable systemic disease. Surgery alone can clear the ctDNA in roughly half of these patients, suggesting the ctDNA source is often the resectable primary tumor, making cystectomy a potentially curative intervention.
Circulating tumor DNA is a powerful tool for detecting systemic minimal residual disease but is not sensitive enough for local, non-muscle invasive recurrences. This limitation means traditional surveillance like cystoscopy remains indispensable, as a negative ctDNA test can provide a false sense of security about local control.
Urinary tumor DNA (utDNA) and circulating tumor DNA (ctDNA) offer complementary information. Used together, they provide superior risk stratification. Patients negative on both tests have a >70% chance of a complete pathological response, while those positive on both have only a ~5% chance, demonstrating clear additive value.