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

This clinical trial tests the safety and best dose of minibeam radiation therapy (MBRT) with a tungsten slit collimator for treating patients with skin or soft tissue tumors that have come back after a period of improvement (recurrent) or that spread from where they first started (primary site) to other places in the body (metastatic). Radiation therapy uses high energy x-rays, particles, or radioactive seeds to kill tumor cells and shrink tumors. Tungsten is an extremely dense metal and is commonly used for blocking x-rays for minimum radiation exposure. A tungsten slit collimator is a device that separates an initially wide beam of x-rays into several very narrow individual beams of radiation. As radiation passes through the collimator, the radiation hits regions of solid tungsten and is blocked. In the open slit regions, radiation passes through to the intended target/tumor area defined by the physician. The tungsten slit collimator then selectively blocks portions of the radiation to create an alternating pattern of higher "peak" and lower "valley" radiation dose regions. These narrow beams of radiation are referred to as "minibeams" and the general approach referred to as MBRT.

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