The consensus for "event-free survival" (EFS) in bladder-sparing trials is now highly inclusive, counting even high-grade superficial (non-muscle invasive) relapses as events. This is a deliberately conservative choice to maximize patient safety and preempt the risk of these relapses leading to metastasis.

For bladder cancer patients with micrometastatic disease, the standard cystectomy requires a significant delay for the operation and recovery. This window may allow unseen metastases to progress, suggesting that upfront, effective systemic therapy is more critical for survival than immediate major surgery.

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.

A key debate in designing the BART trial was whether to irradiate the cystectomy bed only for margin-positive patients. The trial's protocol mandated including the bed for all patients. Subsequent data has validated this decision, showing the entire bed is at risk for recurrence, a crucial finding for radiation field design.

As oncology moves toward bladder-sparing approaches, even highly effective systemic therapies won't be enough. To prevent local relapse and truly avoid cystectomy, a bladder-directed component, such as an intravesical therapy, will be a necessary part of the long-term treatment strategy.

In muscle-invasive bladder cancer, patients whose cell-free DNA remains positive after surgery almost uniformly experience disease relapse. This makes ctDNA a powerful prognostic tool, akin to PSA in prostate cancer, for identifying patients at the highest risk.

High relapse rates (~70%) in surgery-alone arms of recent trials suggest most patients with muscle-invasive bladder cancer (MIBC) already have micrometastatic disease. This reframes the disease, prioritizing early systemic therapy over immediate surgery to achieve control and potential cure.

The rationale for the BART trial was the premise that locoregional relapses after cystectomy are a significant and often overlooked issue. While distant metastases get more attention, a substantial portion of treatment failures are local, causing significant morbidity and contributing to the 40% mortality rate at 2-3 years.

For muscle-invasive bladder cancer patients achieving a complete response to neoadjuvant therapy, a barrier to forgoing bladder removal is local relapse risk. Adding intravesical BCG could prevent these recurrences, making bladder preservation a more viable long-term strategy for these patients.