Data from the BART trial revealed that post-operative patients who experienced a locoregional relapse had a median survival of only 6.5-7 months. This grim prognosis was surprisingly identical to that of patients with distant metastasis, underscoring the critical importance of preventing local disease recurrence.
Despite initial concerns about irradiating the post-cystectomy bed due to bowel proximity, the BART trial demonstrated that using strict Intensity-Modulated Radiation Therapy (IMRT) makes the procedure safe. This approach resulted in only 17-20% grade two acute side effects, a reasonable trade-off for the clinical benefit.
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.
The BART trial investigator posits that adjuvant radiotherapy's role in locoregional control is distinct from immunotherapy's systemic effect. Since their side effect profiles don't overlap, there is a strong rationale for combining these modalities to improve both local and distant control, even without direct comparative data yet.
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.