A Comparison of Thyroid Dose Distribution in 3-D Conformal Radiotherapy and Tomotherapy in Patients with Breast Cancer

Abstract

Background and purpose: During the radiotherapy of breast cancer, especially when the supraclavicular lymph nodes are planned to be treated, a portion of thyroid gland may also be included in the treatment field. In this study we compared thyroid gland dose volume histograms (DVHs) of breast cancer patients receiving radiotherapy, planned in both CT-based three-dimensional planning system and MVCT-based image guidance aspect of helical tomotherapy system. Material and method: 20 breast carcinoma patients who were treated with 3-D conformal radiotherapy technique were evaluated concerning their thyroid gland dose distribution. The estimated minimum, mean and maximum thyroid gland doses were calculated for both 3-D conformal radiothreapy and tomothreapy planning systems. Additionally the volume of thyroid gland that received less than 30 Gy and more than 30 Gy were determined. Results: The maximum, mean and minimum doses of thyroid glands supposed to receive were found to be better with tomotherapy comparing to 3-D conformal therapy plans. The thyroid gland volume that receives more than 30 Gy was smaller in tomothreapy planning system comparing to 3-D conformal therapy planning system. Conclusion: Lower doses of radiation exposure to thyroid gland is possible with Tomotherapy.