Hypofractionated Radiation Therapy for Merkel Cell Carcinoma

This phase II trial tests whether hypofractionated radiation works to treat patients with Merkel cell carcinoma. Radiation therapy uses high energy radio waves to kill cancer cells and shrink tumors. Hypofractionated radiation therapy delivers higher doses of radiation therapy over a shorter period of time and may be more convenient for patients and less immunosuppressive.

Inclusion Criteria: * Patients must have histologically or cytologically confirmed MCC. * Patients must have no evidence of distant metastasis as determined by clinical examination and any form of imaging. * If planned for adjuvant primary tumor radiation therapy a patient should have had surgical excision of a primary MCC tumor within 4 months of starting RT. * If planned for adjuvant nodal radiation therapy a patient should have had: * Prior positive sentinel lymph node biopsy with any degree of nodal involvement within 4 months of starting RT and no completion nodal dissection, or * Lymph node dissection within 4 months of starting RT and high risk nodal disease (receipt of neoadjuvant immunotherapy, ECE, \>1 involved node, \>1 cm nodal disease). * Immunotherapy is permitted at any time and may specifically be administered prior to RT, concurrent with RT or after RT. * Age ≥18 years because MCC is extremely rare in patients \