Nodal Radiation Therapy for Sentinel Lymph Node Positive Melanoma

This study tests whether adding targeted radiation to the lymph nodes can reduce the chance of melanoma returning after a positive sentinel lymph node biopsy (a procedure that checks whether cancer has spread to nearby lymph nodes). Participants will also receive immunotherapy after surgery. **You may be eligible if...** - You have melanoma that tested positive in a sentinel lymph node biopsy - Your lymph node involvement has high-risk features (such as cancer extending outside the lymph node capsule, multiple involved nodes, or cancer invading nearby blood vessels) - You are planned to receive immunotherapy after surgery - There is no evidence of cancer having spread to distant parts of the body - You are in reasonably good overall health **You may NOT be eligible if...** - You have already had a full lymph node dissection (removal of all nearby lymph nodes) - Cancer has spread to distant organs - The area to be treated has already received radiation in the past - You are pregnant Talk to your doctor to see if this trial is right for you.