How do you manage a bladder cancer patient who had a partial cystectomy with a positive margin?

In fewer than 5% of bladder cancer patients, partial cystectomy along with neoadjuvant cisplatin-based chemotherapy can be considered for stage II (cT2, N0) disease with a single tumor in a suitable location and no presence of carcinoma in situ, where an adequate margin of soft tissue and an adequate amount of noninvolved urothelium can be removed along with the tumor without compromising continence or significantly reducing bladder capacity.

A thorough analysis of the surgical specimen is crucia...

Admittedly, I have not seen this precise situation. Presumably, that is because surgeons rarely perform partial cystectomy (radical is the standard of care). If they did and had a positive margin, presumably they would complete the radical and be done. Overall, my enthusiasm for "adjuvant" RT in this setting is low.

As just one option for an otherwise poor-risk patient, which seems very plausible, given the similar toxicities in the accelerated doses of the RAIDER trial, one could consider dose escalation to 70 Gy (assuming optimal bladder location away from abutting bowel), with modified accelerated dose in first phase boost to partial bladder, such as 2.67 x 9 (24 Gy), then follow up with whole bladder tx +/- nodes to 46 Gy, 32 fractions total. Late Gy 3 is equivalent to their 3 Gy in 20 = 72 vs 73 Gy lat...