Radiation to Treat Joint Damage Caused by Cancer Immunotherapy

Inclusion Criteria: * Patients must have histologically confirmed malignancy that is metastatic or unresectable and for which they are receiving single agent or combination immunotherapy or within the last 6 months. * Rheumatologist-established diagnosis of new onset CTCAE grade 2-3 immunotherapy-induced inflammatory arthritis or activated osteoarthritis, involving one or more joints (up to 3) including but not limited to hands, shoulders, elbows, hips, knees and ankles. * Age ≥ 40 years. * ECOG performance status ≤2 (Karnofsky ≥60%). * Patients with ability and willingness to sign consent. Exclusion Criteria: * Contraindications to radiation treatment, such as pregnancy, breast-feeding women and active collagen-vascular disease. * Women of child-bearing potential who have positive urine or serum pregnancy test or refuse to do pregnancy test unless last menstrual cycle was \>1 year prior to consent and/or clear documentation states that the patient is peri- or post-menopausal or there was recent supporting objective evidence of 'no pregnancy' status (e.g. blood or imaging) within 30 days prior to initiation of study treatment. * Have not received systemic steroids within the last 3 months for the treatment of immune related adverse events. * History of prior autoimmune conditions, or concurrent immune related adverse events requiring systemic immunosuppressants. * Estimated life expectancy less than 3 months as assessed by investigators. * Any condition at the discretion of investigator that will preclude participation in the study. * History of secondary malignancy as assessed by investigators. * History of radiation to affected joints as assessed by investigators.