This study will test whether reduced-dose radiotherapy is an effective treatment for metastatic tumors with an ATM mutation. The researchers want to find the lowest dose of radiation that would still be effective to treat these tumors.

Inclusion Criteria:

• Histologically confirmed malignancy with at least one metastatic lesion referred for palliative radiotherapy
• Pathogenic mutation in ATM (somatic and germline allowed)
• ECOG performance status 0-2
• Age ≥ 18 years.
• Able to provide informed consent.
• Patients at reproductive potential must agree to practice an effective contraceptive method during radiation treatments.
• Expected life expectancy of at least 6 months

Exclusion Criteria:

• Previous radiotherapy to the intended treatment site that precludes developing a treatment plan that respects normal tissue tolerances.
• Serious medical co-morbidities precluding radiotherapy.
• Pregnant or breast-feeding women.
• Lesions excluded from de-escalation include regions in which the risk of local disease progression is unacceptably high, including CNS disease and cord compression, and areas in which re-irradiation would not be feasible, including spinal cord overlap.

Memorial Sloan Kettering Cancer Center supports the international committee of medical journal editors (ICMJE) and the ethical obligation of responsible sharing of data from clinical trials. The protocol summary, a statistical summary, and informed consent form will be made available on clinicaltrials.gov when required as a condition of Federal awards, other agreements supporting the research and/or as otherwise required. Requests for deidentified individual participant data can be made beginning 12 months after publication and for up to 36 months post publication. Deidentified individual participant data reported in the manuscript will be shared under the terms of a Data Use Agreement and may only be used for approved proposals. Requests may be made to: crdatashare@mskcc.org.