2Department of Radiation Oncology, Başkent University Faculty of Medicine, Adana Dr. Turgut Noyan Research and Treatment Center, Adana-Türkiye
3Department of Radiation Oncology, İskenderun Gelişim Hospital, Hatay-Türkiye DOI : 10.5505/tjo.2026.4754 OBJECTIVE
We analyzed the dosimetric performance of Helical Tomotherapy (HT) and Volumetric Modulated Arc Therapy (VMAT) for postmastectomy chest wall irradiation (CWI) in patients with left-sided breast cancer, with a particular focus on target volume coverage, organ-at-risk (OAR) sparing, and low-dose exposure to surrounding normal tissues.
METHODS
Twenty patients with left-sided breast cancer who received postmastectomy CWI and regional nodal irradiation were retrospectively evaluated. For each patient, HT and VMAT treatment plans were generated. Dosimetric parameters assessed included planning target volume (PTV) coverage, conformity index (CI), homogeneity index (HI), and dose-volume metrics for OARs. Low-dose exposure to normal tissues was quantified using V10Gy and V25Gy. Statistical comparisons were performed using the Mann-Whitney U test.
RESULTS
Both techniques achieved clinically acceptable PTV coverage and comparable HI. VMAT plans demonstrated significantly better CI than HT (CI: 0.79±0.04 vs. 0.64±0.03; p<0.001). VMAT was associated with significantly lower high-dose exposure to the ipsilateral lung (V20Gy and V30Gy) and heart, and reduced mean dose to the contralateral breast. The VMAT plans also resulted in significantly lower low-dose body volumes (V10Gy and V25Gy) compared to HT. Additionally, VMAT required fewer monitor units and shorter treatment times.
CONCLUSION
Both HT and VMAT are effective for chest wall irradiation in left-sided breast cancer; however, VMAT provides superior dose conformity, improved OAR sparing, and reduced low-dose exposure. These findings support the preferential use of VMAT in clinical settings where minimization of normal tissue exposure and treatment efficiency are priorities.