Dosimetric Evaluation of TF-3DCRT, FIF-Forward IMRT and FF Inversely Optimized IMRT for Breast Conserving Treatment

Objective: To compare the dosimetric characteristic of tangential field 3D conformal (TF-3DCRT, TF), field-in-field intensity-modulated (FIF-IMRT, FIF) and fixed-field inversely optimized intensity-modulated Radiotherapy (FFIO-IMRT, FFIO) for breast conserving treatment, and explore the benefit and efficiency for the three techniques. Materials and Methods: TF-3DCRT, FIF-IMRT and FFIO-IMRT treatment plans were analyzed for 16 breast patients (8 right-sided and 8 left-sided) after breast-conserving surgery. The target and organs at risk (OARs) were contoured by the same physician in the CT images. The prescription dose was 50Gy/25f. TF-3DCRT and FIF-IMRT were designed using Varian Eclipse Ver10.0 planning system, and FFIO-IMRT in the planning system of Pinnacle Ver9.6. Treatment plans were compared according to dose volume histogram (DVH) analysis in terms of PTV homogeneity and conformity indices (HI and CI) as well as OARs dose and volume parameters, and the efficiency was also evaluated. Results: In all cases, the treatment plans showed statistically significant difference between TF-3DCRT, FIF and FFIO-IMRT. The MUs were 244.9±8.3MU vs 285.9±20.3MU vs 534.0±56.2MU (p<0.001), the CIs of dose distribution and the target were 0.40±0.12 vs 0.48±0.12 vs 0.57±0.12 (p<0.01), and the HIs were 0.20±0.02 vs 0.13±0.02 vs 0.17±0.02 (p<0.01). Compared with TF and FFIO, FIF-IMRT showed smaller in the dose of D2 and volume of V107 and V110 in the target. FFIO-IMRT generally increased the D mean, V10 and V20 of ipsilateral lung, the D1 of contralateral breast and the mean dose of contralateral lung, heart, esophagus, and spinal cord relative to TF and FIF techniques. Conclusion: In breast-conserving RT, FIF-IMRT improved the overall quality of dose distribution and delivery efficiency, and the patients are most likely to benefit from FIF-IMRT.