The American Society for Radiation Oncology (ASTRO) has released its first guidelines focused specifically on the use of radiation for bladder cancer.

Like other medical organizations, ASTRO supports trimodal therapy (TMT) — maximal transurethral tumor resection followed by chemoradiation — as a curative alternative to cystectomy for muscle-invasive bladder cancer for select patients.

The guidelines fill in the details for various TMT scenarios, but the advice extends well beyond bladder preservation.

Topics include integrating radiation and immunotherapy, using radiation to improve local control after surgery, using palliative radiation in metastatic disease, and many others. They also offer practical tips on doses, fractionation schedules, treatment fields, radiosensitization, image-guided techniques, and surveillance.

The 34 recommendations are based on a 2009-2024 literature review by a guideline task force that included radiation, medical, and urologic oncologists, as well as a medical physicist and a patient representative. The guidelines were published recently in Practical Radiation Oncology.

The advice includes an extension of TMT beyond its familiar use for muscle-invasive disease to patients with recurrent, high-grade non-muscle invasive bladder cancer (cT1N0M0), a move that’s “potentially surprising,” said task force chair Jason Efstathiou, MD, DPhil.

It’s a conditional recommendation for patients who have exhausted or cannot access other treatments and who decline or are not candidates for cystectomy, based largely on encouraging results from a 37-patient single-arm study.

“This should not be interpreted as a general recommendation for radiation in non-muscle invasive bladder cancer,” Efstathiou, who is a genitourinary radiation oncologist at Mass General Brigham Cancer Institute, Boston, told Medscape Medical News. Meanwhile, for TMT in muscle-invasive tumors, the guidelines distinguish between cN1M0 and cN2-3M0 disease.

ASTRO strongly recommends TMT or radical cystectomy for cN1M0 cancer but makes the nod only conditionally for cN2-3M0 tumors, and then only if they have been stable or responded to neoadjuvant or induction systemic therapy.

“The practical message,” Efstathiou said, is to reassess cN2-3M0 patients for suitability “after systemic therapy, with attention to response, disease extent, and patient fitness.”

For patients who have cystectomies, ASTRO conditionally recommends radiation to reduce local recurrence in patients with pT3-4 tumors or high-risk features such as positive lymph nodes or surgical margins. Treatment fields typically include the tumor bed and involved nodes. The presence of a reconstructed neobladder is not a contraindication to adjuvant radiation, but patients should recover urinary continence first, the group said.

Randomized trials have shown improved local control with adjuvant radiotherapy, but an overall survival benefit has only been shown in retrospective studies.

Adjuvant chemotherapy should be completed beforehand, but how to integrate postsurgical radiation with adjuvant immunotherapy is an “open question,” Efstathiou said.

The guidelines conditionally recommend radiation before or during immunotherapy, based on expert opinion. Giving radiation first, however, may be preferable because safety data for concurrent treatment are limited. Also, since adjuvant immunotherapy can continue for up to a year, delaying radiation until it’s complete is generally not feasible, he said.

For metastatic disease treated with noncurative intent, ASTRO strongly recommends palliative radiation to symptomatic metastases. The group also conditionally recommends radioablation of metastatic sites when there are five or fewer.

For local control and/or palliation, radiation to the bladder in metastatic disease is strongly recommended for patients with more than five metastatic sites and localized symptoms and for local/locoregional disease treated with noncurative intent.

M. Alexander Otto is a physician assistant and award-winning journalist. He is also an MIT science journalism fellow. Email: aotto@medscape.net.