Background: Field-in-field (FIF) technique for treatment of breast cancer has become a widely performed method over the recent years. However, there was no study in the application of FIF technique in patients with breast cancer undergoing mastectomy and lumpectomy. This study is an attempt to compare dosimetric outcomes after applying the FIF technique in these patients. Materials and Methods: Twenty-four patients with right and left breast cancer participated in this study. The FIF planning technique was carried out for patients undergoing mastectomy and lumpectomy using the TiGRT treatment planning system (TPS). For the comparison purpose, we used two main indices, i.e. dose homogeneity index (HI) and conformity index (CI), the number of subfields, as well as mean, maximum, and minimum doses, doses received by 2% (D₂) and 98% (D₉₈) of the target volume, volumes received greater than 107% (V>107%) and less than 95% (V<95%) of the prescribed dose, doses to organs at risk (OARs), and total monitor units (MUs). Results: The results indicated that CI and HI are better in patients with right and left breast lumpectomy surgery (p<0.038 and p<0.047) relative to mastectomy patients (p<0.037 and p<0.029), respectively. Other parameters mentioned in Materials and Methods did not show any significant difference between the two groups of patients (p>0.05). Conclusion: The use of alternative subfields resulted in better dose distribution in target volume with the increase in breast volume. Moreover, to disappear the hot spot areas in isodose curves, it is essential to elevate the number of subfields.
 

Background: In the radiotherapy of patients with esophagus and breast cancer, the heart receives a significant dose of radiation that might cause heart complications. Thefore, the aim of the current study was to evaluate the effects of esophagus and left breast cancer radiotherapy on the cardiac function and to determine the relationship between the dosimetric parameters and ejection fraction (EF) changes. Materials and Methods: Patients with esophageal (n=13) and left breast cancer (n=21) enrolled at our radiotherapy center from March to October 2017. Echocardiography tests were obtained from patients, before and six months after the radiotherapy. Dosimetric parameters were extracted from treatment planning system. The assessed outcomes included pre- and post-radiation EF ratios and percentage change in the EF following radiation.  Results: The mean ± standard deviations of EFs in patients with breast cancer before and six months after treatment were 55.95%±3.2% and 53.10%±6.30% respectively, which were not statistically significant (P = 0.07). In patients with esophagus cancer, the mean ± standard deviations of pretreatment and post-treatment EFs were 56.76%±3.44% and 52.09%±3.88% respectively, which were statistically significant (P = 0.005). Conclusion: The results of our study showed a significant variation of EFs in esophageal cancer patients following radiotherapy, while breast cancer patients treated with radiotherapy showed no significant change. In patients with esophagus cancer, there was a significant correlation between the variation of EFs and volume of heart receiving radiation doses ≥30 Gy (≥V30). Therefore,  to avoid reduction in EF, the use of V20 as a dose-volume constraint is recommended.  

Background: The use of radiation therapy for medulloblastoma can affect children’s visual system. We estimated children’s visual system complication probability in the craniospinal irradiation (CSI) technique with three-dimensional conformal radiotherapy (3D-CRT). Materials and Methods: CSI of fifteen medulloblastoma patients and a phantom were planned with 6 MV photon beams and 23.4 Gy prescribed dose. The doses of lenses were measured using thermoluminescence dosimeters (TLD). The delivered doses and complication probabilities were calculated based on the equivalent uniform dose (EUD) model to each contoured organ, including the bilateral lenses, optic nerves, retinas and optic chiasm. Results: The received dose for each organ was less than the tolerance value (p<0.001), except for the eye lens. The normal tissue complication probability (NTCP) values for all of the organs at risk (OAR) were found insignificant. The discrepancies of calculated and measured doses for the right and left lenses were 6.35% and 6.23% (p<0.001), respectively. Conclusion: The results of this study showed based on the International Commission on Radiological Protection (ICRP) publication 118 that children with medulloblastoma cancer treated with CSI with 3D-CRT method are susceptible to cataract complication.