Dosimetric Comparison of Conventional Radiotherapy, Volumetric Modulated Arc Therapy, and Proton Beam Therapy for Palliation of Thoracic Spine Metastases Secondary to Breast or Prostate Cancer.

Simple Summary: Patients with breast or prostate cancer often develop painful tumors of the spine, i.e., spinal metastases. Treatment of these can be challenging as it is crucial to target the cancer cells without harming nearby healthy tissues. In this dose planning study, we compared three types of radiation therapy (RT) to see which could be most effective for treating spinal metastases while minimizing harm to nearby organs, such as the spinal cord, esophagus, heart, and lungs. Our results suggest that two advanced techniques, Volumetric Modulated Arc Therapy (VMAT) and Proton Beam Therapy (PBT), may be more precise in targeting the tumors and reducing potential harm to other organs compared to traditional palliative RT. These findings indicate that VMAT and PBT may offer better outcomes for certain groups of patients, but more research is needed to understand when these techniques could be appropriate. The aim of this planning study was to compare the dosimetric outcomes of Volumetric Modulated Arc Therapy (VMAT), Proton Beam Therapy (PBT), and conventional External Beam Radiation Therapy (cEBRT) in the treatment of thoracic spinal metastases originating from breast or prostate cancer. Our study utilized data from 30 different treatment plans and evaluated target coverage and doses to vital organs at risk (OARs), such as the spinal cord, heart, esophagus, and lungs. The results showed that VMAT and PBT achieved superior target coverage and significantly lower doses to the spinal cord compared to cEBRT (target: median PTVD95%: 75.2 for cEBRT vs. 92.9 and 91.7 for VMAT (p < 0.001) and PBT (p < 0.001), respectively; spinal cord: median Dmax%: 105.1 for cEBRT vs. 100.4 and 103.6 for VMAT (p < 0.001) and PBT (p = 0.002), respectively). Specifically, VMAT was notable for its superior target coverage and PBT for significantly lower doses to heart, lungs, and esophagus. However, VMAT resulted in higher lung doses, indicating potential trade-offs among different techniques. The study demonstrated the relative advantages of VMAT and PBT over traditional RT in the palliative treatment of spinal metastases using conventional fractionation. These findings underscore the potential of VMAT and PBT to improve dosimetric outcomes, suggesting that they may be more suitable for certain patient groups for whom the sparing of specific OARs is especially important. [ABSTRACT FROM AUTHOR]