Safety and Efficacy of LATTICE Spatially Fractionated Radiation Therapy for Metastatic and/or Bulky Disease

Vollständiger Abstract

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LATTICE radiation therapy (LRT), a 3D spatially fractionated radiation therapy (SFRT), creates high-dose vertices through three-dimensional focusing to generate peak-valley dose distributions while sparing normal tissues. This study assessed its efficacy and toxicity in patients with metastatic and/or bulky tumors. Patients with unresectable bulky and/or metastatic tumors treated with LRT between 4/2017 and 2/2021 were enrolled and retrospectively reviewed. Descriptive statistics were used to summarize patient data. Overall survival (OS) and local control (LC) were estimated using Kaplan-Meier analysis and a competing risk model with death as a competing event, respectively. Clinical response and toxicities were also assessed. A total of 76 patients with 85 lesions were analyzed, including 63 (82.9%) with metastatic disease and 60 lesions (70.6%) classified as bulky tumors. 65.9% (56/85) of patients received one fraction with a median vertex dose of 15 Gy (range, 10–20 Gy), after 30 Gy in two fractions (14, 16.5%). At a median follow-up of 11.6 months, the disease control rate was 91.8%, including 2.4% complete remission, 48.2% partial remission, and 41.2% stable disease. By the end of follow-up, 16 patients (21.1%) remained alive without disease progression. Among the 60 deceased patients, 55 (91.7%) died from disease progression, while 5 (8.3%) died from non-cancer-related causes. Median OS and LC were 11.2 months and 13.7 months, respectively, with 1-year OS and LC rates of 45.9% and 51.9%. Additionally, the local failure rate at 1 year, calculated with death as a competing risk, was 21.2%. Symptomatic improvement was observed in all patients, with no LRT-associated acute or late grade 3+ toxicity. With approximately 50% local control at 1 year, symptom palliation in all patients, and low toxicity, LRT represents a feasible and promising therapeutic strategy for patients with large unresectable tumors, particularly in settings where conventional radiotherapy is limited by toxicity concerns.