Minibeam Radiation Therapy With Tungsten Slit Collimator for the Treatment of Recurrent or Metastatic Skin or Soft Tissue Tumors

Inclusion Criteria: * Age ≥ 18 years * Histologically confirmed malignancy * Primary, recurrent, or metastatic skin or superficial soft tissue tumor amenable to palliative orthovoltage radiotherapy * Anticipated life expectancy ≥ 30 days and anticipated capacity for follow up for ≥ 30 days * Negative pregnancy test done ≤ 28 days prior to registration, for biological women of childbearing potential only * Willing to provide written informed consent * Willing to allow baseline and follow up photograph acquisition for response and toxicity assessment * Willing and able to return to enrolling institution for follow-up during the active monitoring phase of the study * Willing to provide blood and tissue samples for correlative research purposes Exclusion Criteria: * Hematologic, germ cell, or any other tumor that the investigational team would deem to have a high likelihood of clinical complete response with standard palliative radiotherapy (8 Gy in 1, 30 Gy in 10, etc.) * COHORT A (INTACT SKIN) ONLY: Prior radiotherapy targeting the lesion presenting for treatment or prior adjacent radiotherapy if \> 10 Gy overlaps with a portion of the planned target * Treatment with a B-Raf proto-oncogene, serine/threonine kinase (BRAF) inhibitor, monoclonal antibodies targeting vascular endothelial growth factor (VEGF) (bevacizumab or ramucirumab) or small molecule inhibitors inhibiting VEGF within the last 2 weeks or planned treatment with BRAF inhibitor within 4 weeks after radiation * Treatment with an investigational drug therapy within 2 weeks prior to or 4 weeks (the DLT monitoring period) after MBRT * Any tumor with direct extension into the spine such that targeting the spine/spinal cord could not be avoided