WASHINGTON, Oct. 16 -- A bladder cancer patient whose high-grade, finger-like tumors keep returning after BCG treatment now has an FDA-approved drug made for that situation. The agency's reasoning, though, rests on a trial of patients with a different form of the disease.

The Food and Drug Administration on Wednesday expanded Anktiva, given with BCG, to adults whose high-grade, papillary-only non-muscle invasive bladder cancer has not responded to BCG. In August the agency approved daraxonrasib for pancreatic cancer on a randomized Phase 3 trial. This time it leaned on another patient group.

That group had carcinoma in situ, which forms flat patches along the bladder lining. The FDA said in its approval notice that the two tumor types a...