Bladder cancer begins most often in the cells that line the inside of the bladder. Bladder cancer typically affects older adults, though it can occur at any age. The great majority of bladder cancers are diagnosed at an early stage when bladder cancer is highly treatable. However, even early stage bladder cancer is likely to recur. For this reason, bladder cancer survivors often undergo follow up tests for years after treatment to look for bladder cancer recurrence.