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

Overview

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.

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.