Document Type: Conference Proceedings
Medical Physics Department, Isfahan University of Medical Sciences, Isfahan, Iran.
Radiation Oncology Department, Isfahan Milad General Hospital, Isfahan, Iran.
Whole breast radiotherapy after breast-conserving surgery decrease the risk of local recurrence. this study investigates the dosimetric aspects of intensity modulated radiotherapy (IMRT) compared to conventional tangential wedge-based beams techniques (CTT) of the whole breast in early stages breast cancer patients.
Materials and Methods:
Computed tomography images of 35 patients with left sided breast cancer used for whole breast radiotherapy planning were examined. They were planned using four different radiotherapy technique, 1) conventional tangential wedge-based beams techniques (CTT);
2) six beams intensity modulated radiotherapy (IMRT-6F); 3) seven beams intensity modulated radiotherapy (IMRT-7F); and 4) nine beams intensity modulated radiotherapy (IMRT-9F). The PTV dose prescribed was 50 Gy in 25 fractions and V47.5 ≥ 95%. Dose distribution of PTV and OARs, the homogeneity index (HI), and conformity index (CI) were measured and compared to each other.
All of the IMRT plans improved CI (CTT: 0.93 ± 0.019; IMRT-6F: 0.95 ± 0.016; IMRT-7F: 0.96 ± 0.014;
IMRT-9F: 0.97 ± 0.010), HI (CTT: 0.21 ± 0.021; IMRT-6F: 0.17 ± 0.013; IMRT-7F: 0.16 ± 0.014; IMRT-9F: 0.15 ± 0.018), mean dose PTV (CTT: 50.88 ± 0.48Gy; IMRT-6F: 51.93 ± 0.37Gy; IMRT-7F: 51.99 ± 0.38Gy;
IMRT-9F: 52.14 ± 0.33Gy) and significantly increase volume of ipsilateral lung receiving more than 5Gy and 20Gy (V5Gy - V20Gy) (CTT: 20.05 – 12.69; IMRT-6F:41.69 -16.59; IMRT-7F: 42.13 – 16.74; IMRT-
9F: 48.284 - 17.26) too increase mean dose of Heart (CTT: 6.61 ± 1.47Gy; IMRT-6F: 6.33 ± 1.55Gy; IMRT- 7F: 7.35 ± 2.83Gy; IMRT-9F: 8.35 ± 3.64Gy) compared to CTT. Mean dose of contralateral Breast and contralateral Lung too increase than CTT.
From the dosimetric point of view, the IMRT plans were not significantly advantageous over the 3DCRT plans. IMRT produces better the homogeneity and conformity index of the PTV, but increase low doses to OARs.