Fenretinide in Treating Patients Who Have Undergone Surgery for Bladder Cancer

RATIONALE: Drugs used in chemotherapy, such as fenretinide, work in different ways to stop the growth of tumor cells, either by killing the cells or by stopping them from dividing. It is not yet known whether fenretinide is more effective than a placebo in preventing the recurrence of bladder cancer after surgery to remove the tumor. PURPOSE: This randomized phase III trial is studying fenretinide to see how well it works compared to a placebo in treating patients who are at risk for recurrent bladder cancer following surgery to remove the tumor.