Comparison of Dosimetric Parameters Between Field in Field and Conformal Radiation Therapy Techniques in Early Stage of Left Breast Cancer Patients

Breast cancer is the most prevalent cancer in women all over the world. The most common and effective treatment for the early stage of breast cancer patients is breast conserving surgery (BCS) followed by radiotherapy. The aim of this study is to evaluate and compare the dosimetric parameters of three-dimensional conformal radiation therapy (3D-CRT), using virtual wedge and field in field (FIF) techniques for patients having left breast cancer in early stages. Twenty-four patients with left breast cancer participated in this study. They were divided into thr3ee categories (small, medium, and large) based on breast volume: ≤ 1500 cc small, 1500 - 2000 cc medium, and > 2000 cc large. Two treatment planning techniques were generated for each patient by prowess treatment planning system. The following parameters were compared: Maximum, minimum, and mean dose in planning target volume (PTV), homogeneity (HI) and conformity indexes (CI), percentage of volume receiving greater than 107% of the prescribed dose (hot spots) and less than 95% of the prescribed dose (cold spots), and total monitor unit (MU) and doses received to organs at risks (OARs) such as heart and left lung. The mean values were compared using student’s t-test. The FIF technique reduced either the maximum dose in PTV or hot spots in all groups significantly (P < 0.05). Conformity index and cold spots in conformal technique were significantly better than FIF technique in all groups (P < 0.05). Other parameters such as MU, HI, and doses received by OARs did not show any significant difference between two methods in all groups (P > 0.05). It is recommended that two techniques can be combined and used together to cover their weak points. Also, it seems that if there is no equipment of intensity modulated radiation therapy (IMRT) techniques such as FIF in some centers, conformal technique by using virtual wedge is a proper alternative.