Impact of Breast Volume on Dose Distribution and Treatment Planning Quality in Breast Cancer Radiotherapy Using Helical Tomotherapy: A Retrospective Dosimetric Study
Authors: M. Motiur Rahman1,2, Ayesha Siddika Borna2,3, M. Fajle Rabby2, 3, Abdul Kader Zilani3, A.Z.M. Sumsuzoha, AKM Ahsan Habib1.
Institution: 1Department of Radiation Oncology, TMSS Cancer Center (TCC), Bogura, Bangladesh. 2Department of Physics, Rajshahi University (RU), Rajshahi, Bangladesh. 3Department of Physics, Rajshahi University of
Introduction
Breast volume is a factor for women with breast cancer. It can affect how radiation is spread during treatment. Different sizes and shapes of the breast can change how well the radiation hits the target area and how much it affects tissue around it
Methods
This study looked at how breast volume affects the way radiation is given to breast cancer patients using helical tomotherapy. This retrospective dosimetric included 20 breast cancer patients (10 left breast and 10 right breast cancer patients) previously treated with helical tomotherapy.
Results
Planning target volume (PTV) and dosimetric parameters, including D95%, D98%, D2%, V95%, V105%, V107%, homogeneity index (HI), and conformity index (CI), were evaluated to assess target coverage and dose distribution. Mean heart dose, contralateral breast and ipsilateral lung dose-volume parameters were analysed to evaluate OAR sparing. Increasing volume increases the homogeneity index and conformity index greatly. By fixing the contralateral lung below 4 Gy, we obtained a mean heart dose of 7.0 Gy and an ipsilateral lung dose of 13.2 Gy. A large effect of hot spots on breast volume is prominent in dose distribution, where hotspot 107% was found in 0.2 cc volume for maximum PTV volume 1286.49 cc, besides 0.0 cc for smaller volume 582.65. Correlation analysis was performed to evaluate the relationships between PTV volume and various dosimetric parameters, including HI, CI, target dose coverage, hotspot distribution and OAR doses.
Conclusion
This study provided an insight into the influence of breast volume on target dose distribution, dose homogeneity, and OAR sparing in helical tomotherapy-based breast cancer radiotherapy treatment planning. The results may help to find differences in the way treatment is planned and support personalised radiation plans.