Sparing Cardiac Substructures With Optimized Volumetric Modulated Arc Therapy and Intensity Modulated Proton Therapy in Thoracic Radiation for Locally Advanced Non-small Cell Lung Cancer.

PURPOSE: Increasing radiation dose to the heart is associated with worse survival in stage III non-small cell lung cancer. We sought to evaluate the ability of optimized volumetric modulated arc therapy (VMAT) and intensity modulated proton therapy (IMPT) to spare cardiac substructures. We also wanted to determine how a cardiac optimization treatment planning algorithm influences dose distribution to other thoracic organs at risk (OARs). METHODS AND MATERIALS: Cardiac substructures were retrospectively contoured for all patients with stage III non-small cell lung cancer who were treated at our institution with VMAT to 60 Gy in 2-Gy fractions. The structures included valves, atrioventricular node, coronary arteries, chambers, and great vessels. New cardiac-optimized VMAT plans were created to spare these structures while preserving planning target volume coverage and maintaining standard dose constraints to OARs. Dosimetry variables for the new cardiac-optimized VMAT plans were compared via paired t test with the original VMAT plans. IMPT plans were also created, and the cardiac-optimized VMAT plans were then similarly compared with the IMPT plans. RESULTS: Twenty-six patients who were treated from July 2013 to September 2017 were included. Compared with the original VMAT plans, statistically significant improvements were demonstrated for all cardiac structures for the new cardiac-optimized VMAT plans while maintaining or improving appropriate lung, esophagus, and spinal cord constraints and planning target volume coverage goals. Compared with cardiac-optimized VMAT, IMPT demonstrated additional statistically significant improvements for some cardiac dosimetry metrics while maintaining or improving other thoracic OAR constraints. CONCLUSIONS: VMAT is now widely available, and high-quality VMAT plans that incorporate cardiac substructures into the optimization process can provide overall improvements in dose to OARs and, in particular, substantial sparing of critical cardiac structures. IMPT provides some incremental dosimetric improvements beyond cardiac-optimized VMAT, the clinical significance of which remains uncertain.

Development of Late Toxicities in Patients with Oral Tongue Cancer Treated with Surgical Resection and Adjuvant Radiation Therapy.

OBJECTIVES: The late effects of RT are not well reported in patients with oral tongue cancer (OTC). This study reports the incidence of late effects and factors associated with the development of late effects in OTC patients. METHODS: Patients with OTC treated in our institution from 2003 to 2013 were evaluated. The association between RT doses, including mandible maximum and minimum doses and total 3D maximum dose, and late toxicity, defined as development of osteoradionecrosis (ORN), percutaneous endoscopic gastrostomy (PEG) tube dependence for >6 months after treatment, and narcotic dependency >6 months posttreatment were assessed using both univariate and multivariable (MV) analysis. RESULTS: Seventy-six patients with OTC (45% males and 55% females) were treated with definitive surgical resection followed by adjuvant RT. The median follow-up was 4.3 years. Combined late toxicities were reported in 38% of patients. Thirty-four percent of the patients had narcotic dependency and, 3.9% of the patients had ORN of the mandible. Thirteen percent of patients developed PEG tube dependency that was significantly associated with a higher 3D maximum radiation dose on univariate analysis (p < 0.01). On MV analysis, 3D maximum dose remained significantly associated with long-term PEG tube dependency (p = 0.05). CONCLUSION: Patients with OTC treated with adjuvant RT are at significant risk for development of late toxicities. Increasing maximum dose is associated with long-term PEG tube dependence, and care should be taken to reduce the "hot spot" within radiation treatment plans as much as possible.