DISEASE CHARACTERISTICS: Histologically confirmed transitional cell carcinoma of the bladder or mixed histologies containing a component of transitional cell carcinoma Must have undergone radical cystectomy and pelvic lymph node dissection within 12 weeks prior to randomization No evidence of distant metastatic disease on pre- or postoperative radiographic scans No positive surgical margins in the cystectomy specimen and no known macroscopic residual disease left at time of cystectomy No bladder sparing surgery May have undergone continent urinary diversion or neobladder procedure but must have recovered completely from the effects of surgery Must have muscle-invasive disease on final pathologic staging and have a primary tumor stage of pT4, any N, M0, or any pT, N+, M0, or pT3b, any N, any M, and following a pelvic lymph node dissection have a pathologic nodal stage of pN0 (only if pT3b or pT4), pN1, or pN2 Clinically unsuspected organ confined prostate cancer found during cystoprostatectomy allowed