Clinical Experience with Palliative Treatment of Bulky Tumors Using VMAT-Based Lattice Radiotherapy

• Published in: International journal of radiation oncology, biology, physics Vol. 120; no. 2; pp. e229 - e230
• Main Authors: Raiden, B., Descamps, C., Ferraris, G.A., Vazquez, M. F. Diaz, Caussa, L., Gilardi, A., Maciel, F., Rivas, I., Raies, F., Fernandez, D.R.
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 01.10.2024
• ISSN: 0360-3016
• DOI: 10.1016/j.ijrobp.2024.07.516

The purpose of this work was to demonstrate the feasibility of palliative treatment for patients with advanced bulky tumors using high-dose 3D Lattice radiotherapy and to present our clinical experience using volumetric modulated arc therapy (VMAT) with respect to its deliverability and clinical tolerance. In this study, 63 patients (mean age of 61 [8-98], 30 (48%) females and 32 (52%) males) with different kinds of bulky tumors (>45cc) were treated between Jun 2020 and January 2024. Regarding the primary tumor, 19 patients (31%) had adenocarcinoma histology, 24 (45%) squamous carcinoma, 12 (19%) sarcomas and 5 (8%) others. All cases had received previous systemic treatment, without response and with tumor progression; considered inoperable. In order to create a highly heterogeneous dose distribution, vertices (1cm-diameter spheres) were created throughout the tumor volume with about 3 cm of separation. The mean dose prescribed to vertices was 15Gy [12-18Gy] in one fraction and to the rest of the tumor between 20 y 72Gy delivered in 5 to 30 fractions. Plans were generated using IMRT techniques in the Eclipse treatment planning system (AAA, v11). Quality control of the delivered dose was realized following SRS international recommendations. Treatments were delivered with 6MV X-ray beam. The initial tumor mean volume was 519cc [48-2600] and a mean vertices number of 16 [2-97] was created within the tumor. All the VMAT plans calculated showed highly spatially modulated dose distribution in the tumor with V50% and V2% of the vertices dose respectively >13Gy and >15Gy with peak-to-valley ratio comparable with former grid therapy techniques. All quality controls passed our institutional tolerances. Concerning toxicities, 11 (18%) patients presented grade 1-2 gastrointestinal toxicity, 16 (26%) patients presented skin toxicity (15 (24%) grade 1-2 and 1 (1.6%) grade 3-4), 12 (19%) patients manifested mucositis, 5 (8%) of which grade 1-2 and 7 (11%) grade 3-4. With a mean follow-up of 6 months [1-28], 34 (55%) patients remained with stable disease, 21 (34%) patients had a partial response, 5 (8%) patients had a complete response, and 2 (3%) patients progressed. With modern radiotherapy methods using VMAT techniques, it is now possible to deliver safely and efficiently Lattice radiotherapy inside large tumor volume, in reduced treatment times. Lattice techniques can be offered in cases of patients with voluminous, inoperable tumors with acceptable tolerance and tumor response. Increased patient number and long-term follow-up could be crucial for accurately assessing treatment effectiveness, including post-treatment metabolic studies to better understand long-term effects.