Preoperative Radiotherapy and Immunotherapy for Sinonasal and Anorectal Mucosal Melanoma

This trial is testing whether adding radiation therapy before surgery to combination immunotherapy improves outcomes for people with mucosal melanoma — a rare type of melanoma that develops inside the body (such as in the nasal passages or rectum) rather than on the skin. **You may be eligible if...** - You have mucosal melanoma in the nasal/sinus area or the anorectal region confirmed on imaging or exam - There is no evidence of distant spread (metastasis) - You are planned to receive combination immunotherapy (such as ipilimumab + nivolumab) - You are 18 or older and in acceptable physical condition (ECOG ≤3) **You may NOT be eligible if...** - Your cancer has spread to distant organs - You have had prior immunotherapy for this cancer - You have serious autoimmune disease - You are pregnant or unable to use effective contraception - You have had prior radiation to the relevant treatment area Talk to your doctor to see if this trial is right for you.