It may be safe to expand the pool of patients with localized muscle-invasive bladder cancer (MIBC) eligible for bladder preservation. As confirmed in a combined analysis of two clinical trials, patients with a near-complete response (Ta or Tis) at the time of cystoscopic evaluation after the induction phase of bladder-conserving treatment experienced no increase in the incidence of bladder recurrence or salvage cystectomy when compared with patients with a complete response (T0) (Abstract 284).
“We recommend that patients with a near-complete response to the induction phase continue with their bladder-sparing therapy,” said lead investigator Timur Mitin, MD, PhD, of Massachusetts General Hospital.
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Bladder-preserving therapy for MIBC has evolved markedly from the 1970s with the addition of radiosensitizing chemotherapy and more refined radiation techniques. Today, the standard approach is to perform transurethral resection followed by induction chemoradiotherapy. Patients free of disease based on cystoscopic evaluation proceed to consolidation chemoradiotherapy, whereas those with persistent disease proceed immediately to radical cystectomy.
Consolidation chemotherapy has typically been reserved for patients with a complete tumor response. However, as Dr. Mitin explained, “Many physicians have been reluctant to subject patients to radical cystectomy if after the induction chemoradiotherapy they find very small amounts of superficial tumor—Ta or Tis.”
To explore whether bladder preservation is appropriate for patients with a near-complete response, two recent Radiation Therapy Oncology Group (RTOG) trials, 9906 and 0233, relaxed the standard treatment algorithm and permitted patients with a near-complete tumor response after induction therapy to proceed to consolidation.
To determine how well the Ta/Tis group fared compared with the T0 group, Dr. Mitin and colleagues pooled data from RTOG 9906 and 0233 to better evaluate outcomes. Merging the data sets yielded 119 eligible patients who proceeded to consolidation after responding well to induction chemoradiotherapy—101 (85%) with T0 and 18 (15%) with Ta or Tis.
After being followed for a median of 5.9 years, bladder recurrence rates reached 35.6% for patients with a T0 response and 27.8% for patients with a Ta/Tis response—a difference that was not statistically significant (p = 0.52). The incidence of invasive bladder recurrence also proved statistically similar between the two groups, reaching 36.1% for patients with a T0 response and 20.0% for patients with a Ta/Tis response (p = 0.53). In accord, salvage cystectomy occurred at similar rates in the two groups.
With regard to survival, 72% of patients with T0 remained alive at 5 years, as compared with 61% of patients with Ta/Tis—another statistically similar finding (p = 0.1198). Dr. Mitin noted that disease-specific survival and bladder-intact survival also did not differ significantly between the two groups.