Dosimetric analysis of patients receiving volumetric-modulated arc palliative radiotherapy to the thoracic spine: A comparison with conventional mono-isocentric parallel opposed pair treatment.

Purpose: Volumetric modulated arc therapy (VMAT) has allowed for dose escalation and a decrease in radiation-induced toxicities for a variety of treatment sites, including spinal metastases. This article will compare the dosimetric impacts on normal lung tissue in patients treated with both VMAT and conventional treatment to the thoracic spine and determine if any significant difference exists among patient reported Edmonton Symptom Assessment System (ESAS) scores.

Methods: This retrospective quality assurance study identified 288 patients who received palliative radiotherapy to the thoracic spine using VMAT or conventional planning techniques with various palliative dose fractionation schemes. V5 lung dose levels, treated planning target volume (PTV) cord length, patient-reported ESAS scores at the time of radiation oncology consultation, 3 months' post-treatment, and 6 months' post-treatment were analyzed. All symptoms on the ESAS survey were investigated, but shortness of breath (SOB) scores were the main focus of this study. Date of death for each patient was also included for analysis.

Results: Patients treated with a VMAT technique had significantly higher V5 lung dose levels compared to those treated conventionally (right lung: p = 1.67e-14; left lung: p = 1.33e-6). Despite this, no significant differences were observed for SOB scores at all time points between groups and conventionally treated patients reported significantly worse pain, tiredness, depression, and wellbeing scores. A moderate correlation was observed between PTV length and nausea, SOB, appetite, and drowsiness scores in the VMAT group. Treatment technique was not found to have a significant impact on patient lifespan.

Conclusions: Despite higher V5 lung dose levels associated with a VMAT technique, no significant differences were found in patient-reported ESAS scores compared to patients treated with conventional techniques. This demonstrates that palliation of thoracic spinal metastases is feasible and safe using a VMAT technique.