Evaluation of Healthy Tissue Dose at Different Regions between Volumetric-Modulated Arc Therapy and Intensity-Modulated Radiation Therapy Plans in the Treatment of Various Cancers.

Background: Radiotherapy plays an important role in the management of cancer. Although the improved technologies increase therapeutic index, different delivery techniques deliver different dose pattern to the healthy tissue within and outside treatment volume.

Objective: The objective of this study was to evaluate the low, intermediate, and high dose to healthy tissue within and outside the treatment volume and to find the relation between tumor volume and various doses received healthy tissue volume.

Materials And Methods: A total of 150 patients were included. For all patients, planning computed tomography images were acquired. Tumors, critical structures, and healthy tissue volumes at different regions were delineated. Two sets of plans, one with volumetric-modulated arc therapy and another with intensity-modulated radiation therapy (IMRT) were created, optimized for 6 MV photons and dose was calculated. Dosimetry results for tumor, organs at risks (OARs), and healthy tissue from both the techniques were evaluated and compared.

Results: Tumor coverage and dose to OARs was significantly better with volumetric-modulated arc therapy (VMAT). Volume of healthy tissue received high-dose within the treatment volume as well as volume of healthy tissue received low and intermediate-dose out of treatment volume were significantly ( < 0.002) lesser with VMAT. Besides, the results showed that as the tumor volume increased, the various dose received healthy tissue volume also increased.

Conclusions: VMAT plan can reduce the risk of secondary malignancy while treating different sites of cancer. VMAT is the most appropriate technique than IMRT, especially in the treatment of large tumor volume. Special attention has to be given, especially while treating women and children.