Radiation Pneumonitis: Proton Therapy Local Dose Response and Clinical Symptoms
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Abstract
Radiation pneumonitis (RP), a major toxicity following thoracic radiotherapy (RT), is expected to diminish with proton therapy. RP due to MV x-ray RT appears on FDG PET imaging as metabolic enhancement within the lungs with a linear dose response. This study evaluates the relationship between local proton radiation dose and pulmonary toxicity in esophagus cancer patients. 96 patients treated with chemoradiotherapy were selected for this study. Their treatment planning CT was registered with the restaging PET/CT. The lung standard uptake values (SUV) were evaluated using a slope of the normalized SUV versus radiation dose which corresponded to the pulmonary metabolic radiation dose response (PMRR). CTCAEv4 clinical RP scores were and modeling was performed to determine correlations between PMRR, standard dosimetric parameters, and RP clinical outcomes. Regression modeling of the normalized SUV vs proton dose found adequate correlation between these two variables, with mean PMRR values of 0.020 and 0.011 for the symptomatic and asymptomatic respectively. Dosimetric parameters were also found to be significantly higher for the symptomatic group. The dose response reported in this study is similar to to that seen for MV x-ray RT and may be used to estimate the proton Relative Biological Effectiveness (RBE) for RP.
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This presentation is supported by the National Cancer Institute through the U54 CA096297/CA096300: UPR/MDACC Partnership for Excellence in Cancer Research Training Program.
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