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

PRIMARY OBJECTIVE: I. To determine the maximum tolerated dose (MTD) of MBRT and describe the adverse events of treatment. SECONDARY OBJECTIVE: I. To assess the ability to maintain a distinct differential between peak and valley doses using film dosimetry. EXPLORATORY OBJECTIVES: I. To estimate the rate of freedom from local progression at 6 and 12 months after the start of MBRT. II. To evaluate pre-treatment and post-treatment differential abundance of peripheral blood immune cell populations and their activation markers. III. Explore germline and somatic mutations in homologous recombination (HR) genes and their association with freedom from local progression. IV. Quantify the immune phenotypes and cell signaling in the tumor microenvironment pre-MBRT and post-MBRT using bulk ribonucleic acid (RNA)-sequencing (seq) data. OUTLINE: Patients undergo MBRT with a tungsten slit collimator over 2-3 fractions on study. Patients also undergo standard of care CT simulation on study and undergo collection of blood samples and punch or core biopsy throughout the study. After completion of study treatment, patients are followed up at weeks 2, 4, and 12, and months 6, 9, and 12.