Intensity Modulated Radiotherapy (IMRT) Versus Dynamic Wedge Techniques in Radiation Therapy of the Breast; Impact on Dosimetric Parameters and Radiation dose to Contralateral Breast

Background: New techniques of radiation therapy are being introduced in the management of breast cancer. One of the most rapidly emerging new techniques is intensity modulated radiotherapy (IMRT). Aim of the Study: The purpose of the study is to compare between two different techniques of radiation therapy of breast cancer for intact breasts after breast conservative therapy (BCT); IMRT and dynamic wedge (DW) (standard technique) regarding their impact on dosimetric features of the treated breast and the radiation dose received by the contralateral breast. Patients and Methods: Fourteen female patients with breast cancer treated with BCT and referred for adjuvant radiation therapy at radiation therapy department of King Abdulaziz University hospital; Jeddah Saudi Arabia during the period January 2007-August 2007 had been studied. Their archived CT scans for breasts were retrieved and the two plans (IMRT and dynamic wedge techniques) were implemented in those CT cuts. The dosimetric parameters (maximum dose; minimum dose, mean dose and homogeneity index) for the treated breast as well as the radiation dose received by the other breast (at 5%, 50% and 95% of its volume) were compared between the two techniques. Results: Fourteen patients had been included in the study; their mean age was 44.9 years; 8 were left sided, and 6 right sided and all of them had been referred for radiation therapy after BCT. The mean radiation dose received by DW technique was 50.68 Gy as compared to 51.23 by IMRT (p value: 0.023), the mean homogeneity index (HI) of dynamic wedge technique was 15.36 (± 39 SD) as compared to 7.02 for IMRT ( p value 0.001). Regarding the radiation therapy dose received by the contralateral breast; it had been found that in DW technique; the 5%; 50% and 95% of the volume of the contralateral breast received a mean radiation dose of 1.16 Gy, 0.31 Gy, and 0.097 Gy respectively as compared to 4.11 Gy, 1.33 Gy and 0.82 Gy respectively; a highly significant difference ( p value: Correspondence to: Dr. Ehab Esmat Fawzy Radiation Oncology department King Abdulaziz University Hospital. Contact: Telephone: 00966505586568 Email: [email protected] 0.0001) with significantly higher dose to contralateral breast by IMRT technique as compared to DW technique. Conclusion: Although the IMRT technique achieved a better dose homogeneity as compared to dynamic wedge technique; however; the radiation dose received by the contralateral (normal) breast was significantly higher in IMRT technique. So we have to be cautious if we want to implement the IMRT technique in radiation therapy of breast to avoid unnecessary radiation exposure to the contralateral breast with its possible impact on late incidence of carcinogenesis.