2928 - Comparative Evaluation of IMRT and VMAT Techniques with Deep Inspiration Breath Hold for Right-Sided Breast Cancer: Dosimetric and Organ Sparing Outcomes
Presenter(s)
M. Cokelek1, M. W. T. Chao2, S. F. Lee3, F. Foroudi4, P. Moorfoot5, and S. Le-Nguyen5; 1Genesis Cancer Care, Melbourne, Australia, 2Ipsen, Glen Waverley, VIC, Australia, 3Department of Radiation Oncology, National University Cancer Institute, National University Hospital, Singapore, Singapore, 4Olivia Newton John Cancer Wellness and Research Centre, Austin Hospital, Melbourne, VIC, Australia, 5GenesisCare, Melbourne, Australia
Purpose/Objective(s): This study evaluates the efficacy of Intensity-Modulated Radiation Therapy (IMRT) and Volumetric Modulated Arc Therapy (VMAT), with and without Deep Inspiration Breath Hold (DIBH), for treating right-sided breast cancer. We hypothesized that VMAT provides superior Planning Target Volume (PTV) coverage compared with IMRT while maintaining acceptable organ-at-risk (OAR) sparing, and that VMAT-DIBH reduces OAR doses compared to VMAT-FB.
Materials/Methods: A paired comparison study was conducted for 32 patients each having IMRT-FB, IMRT-DIBH, VMAT-FB, and VMAT-DIBH plans. PTV and OARs were contoured per RTOG guidelines. Dosimetric parameters included PTV coverage at 95% of the prescribed dose (PTV4005), mean heart dose, right lung volume receiving 20Gy (V20Gy), and liver dose at 2cc. Pairwise Wilcoxon signed-rank tests were used to compare plan metrics. A p-value <0.05 was considered statistically significant. Repeated-measures linear mixed-effects models were used to account for the within-patient correlation. Technique (IMRT vs. VMAT) and breathing mode (FB vs. DIBH) were treated as fixed effects, with random intercepts for patients.
Results: VMAT-FB achieved superior PTV4005 coverage (median 99.5%) compared to IMRT-FB (median 93.4%, p<0.001), but it resulted in slightly higher mean heart dose (0.86 Gy vs. 0.40 Gy, p<0.001) and right lung V20Gy (12.6% vs. 11.3%, p=0.016), while the liver dose at 2cc was lower (13.3 Gy vs. 16.5 Gy, p=0.006). When maintaining PTV coverage, adding DIBH to VMAT (VMAT-DIBH) preserved PTV4005 coverage (99.5% vs. 99.5%, p>0.05) while significantly reducing mean heart dose (0.77 Gy vs. 0.86 Gy, p=0.002), right lung V20Gy (11.5% vs. 12.7%, p<0.001), and liver dose at 2cc (3.0 Gy vs. 13.3 Gy, p<0.001).
Conclusion: VMAT provides superior PTV coverage compared to IMRT but at the cost of higher doses to some OAR under free-breathing conditions. Incorporating DIBH into VMAT significantly reduces doses to the heart, right lung, and liver while preserving excellent target coverage. These findings highlight the critical role of DIBH in optimizing treatment plans, particularly when PTV coverage is prioritized for right-sided breast cancer.