KEY POINTS
- This single-center retrospective study included 60 patients treated between February 2023 and May 2025 for bulky tumors, defined as parenchymal lesions ≥5 cm or metastatic nodes ≥2 cm. 88.3% had stage IV disease, half had ECOG performance status ≥2, and median tumor volume was 288.2 cm³.
- Treatment was palliative and used two spatially fractionated approaches: lattice radiotherapy in 18 patients and stereotactic central/core ablative radiotherapy in 42. High-dose vertices were placed within the tumor while maintaining spatial separation and distance from adjacent organs at risk; median vertex biologically effective dose was 88 Gy.
- Symptom relief at 2–4 weeks occurred in 55/60 patients (91.7%). Pain improved in 38/41 (92.7%), dyspnea in 13/13, hemorrhage in 2/2, and tenesmus in 2/2; the single cases of bowel obstruction and portal hypertension did not improve.
- Among 51 patients with follow-up imaging, tumor size decreased in 45 (88.2%). RECIST 1.1 best response included 17 partial responses (33.3%), 32 stable diseases (62.7%), and two progressive diseases (3.9%), producing a disease-control rate of 96.1%.
- Higher dose to the vertices was the only significant response-associated variable in univariate analysis. With BED-Vertex ≥88 Gy, partial response occurred in 48.0% versus 19.2% below 88 Gy, with no progressive disease in the higher-dose subgroup (P=.020).
- Concurrent immunotherapy showed a numerical but nonsignificant response signal: partial response occurred in 46.2% of patients receiving immunotherapy versus 28.9% without it. The study was not designed to determine whether immunotherapy contributed to SFRT efficacy.
- Median overall survival was 7.6 months (95% CI 4.3–10.9) after median follow-up of 15.8 months. No grade ≥3 toxicity was recorded; reported events included grade 1 pneumonitis in 5%, grade 1 hepatotoxicity in 5%, and grade 2 dermatitis in 3.3%.
CLINICAL TAKEAWAY
SFRT produced rapid symptom improvement in a heavily pretreated population with very large tumors and little reported severe toxicity, supporting continued investigation as a palliative option when homogeneous high-dose treatment is difficult. However, the mixed histologies, variable fractionation, retrospective symptom assessment and lack of standardized dosimetry mean neither the 92% relief rate nor the apparent BED-response relationship should yet guide routine dose escalation.