A Five-Year Institutional Experience With Spatially Fractionated Radiation Therapy for Palliative Management of Bulky Tumors Across Diverse Anatomical Sites

Introduction Treating bulky tumors that are ineligible for surgery or resistant to chemotherapy is a significant and challenging problem. High-dose, high-precision radiation therapy is an alternative for these patients. Spatially fractionated radiation therapy (SFRT) utilizes a combination of high radiation doses targeted in an equidistant configuration and random distribution to the tumor and low-radiation doses with homogenic distribution to induce an immunological response against the tumor. The present series explores our five-year experience using SFRT as palliative treatment for bulky tumors from different anatomical locations. Methods From March 2019 to June 2024, we treated 21 patients with bulky tumors (>6 cm) in different anatomical locations with SFRT. Patients received doses of 18-24 Gy in high-dose regions and 5 Gy in low-dose regions. Tumoral response was evaluated through Response Evaluation Criteria in Solid Tumors (RECIST) criteria. Additionally, toxicity, changes in quality of life, and overall survival were measured. Results After an average follow-up of 36 weeks, 52% (n=11) patients maintained a stable disease, 38% (n=8) had a partial response, 4.76% (n=1) had a complete response, and 4.76% (n=1) had disease progression. The average tumor size at the end of treatment was 12.89 cm (SD=9.48) compared to the initial size of 15.19 cm (SD=7.48) (T-test, p=0.014). Patients had a decrease in the Visual Analogue Scale (VAS) score from 6.2 (SD=3.0) before treatment to 1.1 after (SD=1.46) (T-test, p=0.001). Also, patients had a global quality of life index of 0.8 at the last follow-up, with an average survival of 53 weeks. No patient presented toxicity greater than grade 2 on the Radiation Therapy Oncology Group (RTOG) scale. Conclusions SFRT seems to be effective for the palliative treatment of bulky tumors, as proved by the reduction of tumor volume and size, decrease of pain intensity, and improved quality of life in this series. However, randomized studies must be performed to establish the efficacy of this treatment further.