Abstract:
Objective To evaluate the differences in dosimetry distribution among three different radiotherapy methods used for the treatment of left breast cancer affecting the total breast, clavicle, and internal breast lymphatic drainage area after breast-conserving surgery. The target coverage and organs at risk (OARs) in each method were compared.
Methods Twenty breast cancer patients who were treated at First Affiliated Hospital of Kunming Medical College, from January 2018 to October 2019 were selected. All patients underwent left-side breast conserving postoperative radiotherapy. Dynamic multi-leaf collimator (dMLC), volumetric modulated arc therapy (VMAT), and helical tomotherapy (HT) plans were designed for each patient. We compared and analyzed the parameters of planning target volume of the tumor bed (PTVtb), planning target volume (PTV), and OARs according to these plans using a paired t-test.
Results The mean dose (Dmean), D1, homogeneity index (HI) of PTVtb, Dmean, and conformity index (CI) of the PTV of the HT plan were better than those of the DMLC and VMAT plans. The Dmean, V5, V10, and V30 of the heart and lungs were significantly decreased in the HT plan. The HT plan had the lowest Dmean and D1 values for the left anterior descending coronary artery and right coronary artery. However, compared with the VMAT and DMLC plans, the HT plan had increased values for D1 and Dmean of the right breast.
Conclusion For patients with left breast cancer who have undergone breast conserving surgery, HT can reduce the dose to the ipsilateral lung and heart. However, the low-dose area of the contralateral lung was larger with the HT plan than with the VMAT and dMLC plans. With the dMLC plan, the dose to the contralateral lung was the lowest, but the doses to the ipsilateral lung and heart were higher than those with the VMAT and HT plans. An appropriate treatment plan should be chosen according to the condition of the patient.
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