Dosimetric Analysis of Tangential-Based Volumetric Modulated Arc Therapy Implemented Using Deep Inspiration Breath-Hold Technique in the Left Breast Cancer Patients with Breast-Conserving Surgery

OBJECTIVE We aimed to report the dosimetric effects of integrating the deep inspiration breath-hold technique (DIBH) into tangential-based volumetric modulated arc therapy (TVMAT) in left breast cancer patients who underwent breast-conserving surgery (BCS). METHODS Sixty-one patients who underwent BCS were included in the study. Patients were divided into two groups according to whether irradiation was applied only to the breast or to the breast + regional lymph nodes (RLN). DIBH-TVMAT and free-breath (FB)-TVMAT plans were generated using a mono-isocentric technique with two partial arc rotations for each patient. The same gantry angles were used for both FBTVMAT and DIBH-TVMAT plans. DIBH-TVMAT and FB-TVMAT plans were evaluated, and dosimetric parameters were compared. RESULTS The mean cardiac dose in the FB-TVMAT and DIBH-TVMAT plans was 8.8 Gy and 5 Gy, respectively, indicating a 42% dose reduction in patients receiving only breast radiotherapy (RT) (p=0.000). Left lung volumes that received 5 Gy and 20 Gy were also significantly in favor of DIBH-TVMAT (p=0.001; p=0.003). A 23% reduction was encountered in the maximum dose applied to the left anterior descending coronary artery (LADCA) after the DIBH-TVMAT plan in patients who received RT to the breast and RLN (p=0.000). The addition of supraclavicular lymph nodes to the treatment field revealed an increase in the heart volume that received 5 Gy and the ipsilateral lung volumes that received 5, 10, and 20 Gy. CONCLUSION The technique integrating DIBH with TVMAT provides a significant dose reduction not only to the heart and LADCA but also to the bilateral lungs and contralateral breast without sacrificing target volume dose coverage.