V.A. Dumane

Dosimetric Comparison of Volumetric Modulated Arc Therapy, Static Field Intensity Modulated Radiation Therapy, and 3D Conformal Planning for the Treatment of a Right-Sided Reconstructed Chest Wall and Regional Nodal Case

We compared 3D conformal planning, static field intensity modulated radiation therapy (IMRT), and volumetric modulated arc therapy (VMAT) to investigate the suitable treatment plan and delivery method for a right-sided reconstructed chest wall and nodal case. The dose prescribed for the reconstructed chest wall and regional nodes was 50.4 Gy. Plans were compared for target coverage and doses of the lungs, heart, contralateral breast, and healthy tissue. All plans achieved acceptable coverage of the target and IMNs. The best right lung sparing achieved with 3D was a V20 Gy of 31.09%. Compared to it, VMAT reduced the same by 10.85% and improved the CI and HI over 3D by 18.75% and 2%, respectively. The ipsilateral lung V5 Gy to V20 Gy decreased with VMAT over IMRT by as high as 17.1%. The contralateral lung V5 Gy was also lowered with VMAT compared to IMRT by 16.22%. The MU and treatment beams were lowered with VMAT over IMRT by 30% and 10, respectively, decreasing the treatment time by >50%. VMAT was the treatment plan and delivery method of choice for this case due to a combination of improved lung sparing and reduced treatment time without compromising target coverage.

Dose to organs in the supraclavicular region when covering the Internal Mammary Nodes (IMNs) in breast cancer patients: A comparison of Volumetric Modulated Arc Therapy (VMAT) versus 3D and VMAT

During breast/chest wall and regional nodal irradiation (RNI), standard 3D conformal techniques can fail to meet the dosimetric constraints for the heart and ipsilateral lung. VMAT can improve the dosimetric sparing of the heart and lungs. However the unnecessary increase in dose to the organs in the supraclavicular region as a result of using VMAT can be avoided. In this work we investigate potential dosimetric advantages of combining 3D with VMAT to improve sparing of these organs. Ten breast cancer patients requiring radiation therapy to the breast/chest wall and RNI including the IMNs, and who did not have a viable 3D conformal plan were chosen for the study. Each patient was planned with VMAT and with a combination of 3D for the supraclavicular region and VMAT for the breast/chest wall followed by a dosimetric comparison. Prescription dose was 50.4 Gy in 28 fractions. For similar coverage to the PTV and IMNs, doses to the esophagus and cord were reduced by 17.8 Gy and 15.5 Gy while mean dose to the thyroid and larynx were also reduced by 16.5 Gy and 11.7 Gy respectively. Maximum brachial plexus dose was the same in both techniques. The ipsilateral lung V20Gy increased by 3.1% but was still < 30%. No significant differences were noted in doses to the heart, total lung and contralateral breast. However V5Gy to the contralateral lung was reduced by 8.5% with the combined plan. Using 3D conformal planning for the supraclavicular region and VMAT over the breast/chest wall improves sparing of the esophagus, cord, thyroid and larynx while reducing low dose exposure to the contralateral lung and does not compromise doses to the heart, ipsilateral lung and total lung.