Consideration of lung dose changes when establishing lung cancer treatment plans according to tumor changes

Abstract

PurposeThe purpose of this study was to determine if treatment dose to the lungs can be considered in the initial treatment planning according to change in tumor size during treatment. MethodsLung dose was evaluated in 26 patients who underwent re-planning CT (reCT) due to changes in tumor size during lung cancer treatment with intensity-modulated radiotherapy (IMRT) and volumetric-modulated arc radiotherapy (VMAT). Relevant parameters were V5, V10, V20, V30, V40, and mean lung dose. ResultsDose parameters to most lungs followed a normal distribution, but there were no statistically significant results for changes in lung dose after reCT. Patients with only lungs surrounding the tumor tended to have a 7.6% decrease in mean bilateral lung dose (MBLD) as tumor volume decreased. In contrast, patients with ribs and vertebrae within the target region showed a 5.9% increase in MBLD. Mean dose to the bilateral lungs before and after reCT increased (positively correlated) with high-density material in the planned target volume (PTV). ConclusionsThis study found a correlation of radiological dose to the lungs to presence of high-density material in the PTV. In such patients, reducing lung dose in the initial treatment plan is expected to reduce radiation side effects.