SU-F-T-133: Uniform Scanning Proton Therapy for Lung Cancer: Toxicity and Its Correlation with Dosimetry.

PURPOSE: To analyze the toxicity of uniform scanning proton therapy for lung cancer patients and its correlation with dose distribution.

METHODS: In this study, we analyzed the toxicity of 128 lung cancer patients, including 18 small cell lung cancer and 110 non small cell lung cancer patients. Each patient was treated with uniform scanning proton beams at our center using typically 2-4 fields. The prescription was typically 74 Cobalt gray equivalent (CGE) at 2 CGE per fraction. 4D Computerized Tomography (CT) scans were used to evaluate the target motion and contour the internal target volume, and repeated 3 times during the course of treatment to evaluate the need for plan adaptation. Toxicity data for these patients were obtained from the proton collaborative group (PCG) database. For cases of grade 3 toxicities or toxicities of interest such as esophagitis and radiation dermatitis, dose distributions were reviewed and analyzed in attempt to correlate the toxicity with radiation dose.

RESULTS: At a median follow up time of about 21 months, none of the patients had experienced Grade 4 or 5 toxicity. The most common adverse effect was dermatitis (81%: 52%-Grade 1, 28%-Grade 2, and 1% Grade 3), followed by fatigue (48%), Cough (46%), and Esophagitis (45%), as shown in Figure 1. Severe toxicities, such as Grade 3 dermatitis or pain of skin, had a clear correlation with high radiation dose.

CONCLUSION: Uniform scanning proton therapy is well tolerated by lung cancer patients. Preliminary analysis indicates there is correlation between severe toxicity and high radiation dose. Understanding of radiation resulted toxicities and careful choice of beam arrangement are critical in minimizing toxicity of skin and other organs.