Journal of Clinical and Diagnostic Research, 2018, Vol-12(10): XC01-XC04 1 1 DOI: 10.7860/JCDR/2018/31495.12073 Original Article Oncology Section Dosimetric Comparison between Two Different Intensity Modulated Radiation Therapy and 3D-Conformal Radiation Therapy Planning Techniques for Carcinoma of Breast Following Conservative Surgery MICHELLE D’ALMEIDA 1 , JYOTHI NAGESH 2 , RAMYA BALASUBRAMANIAN 3 , SRINIDHI GURURAJARAO CHANDRAGUTHI 4 , SARATH S NAIR 5 , SHREEKRIPA 6 , KRISHNA SHARAN 7 ABSTRACT Introduction: The anatomy of the chest wall is curved which makes it quite complicated to plan radiation therapy for breast cancer. There are different techniques for delivering external beam radiation therapy. Therefore, it is essential to know the technique by which we can render a better treatment. Aim: To compare and analyse three different planning techniques namely Three Dimensional Conformal Radiation Therapy (3DCRT), two field Intensity Modulated Radiation Therapy (IMRT) and multiple field IMRT using dosimetric parameters. Materials and Methods: In this retrospective dosimetric study, we evaluated 10 breast cancer patients. For each patient, three plans namely 3DCRT, two field IMRT and multiple field IMRT (7 beams) were generated on the computed tomographic images using Oncentra Treatment Planning system. A dose of 50Gy in 25 fractions was prescribed to the Planning Target Volume (PTV). The plans were compared with each other on volume coverage (conformity and homogeneity) and organ-at-risk sparing. Paired t-test was used for identifying statistical differences between the plans. A significance level, p=5% or 0.05 was chosen. Results: The dose conformity was best by multiple field IMRT (p=0.0001). Both two field IMRT and multiple field IMRT provided more homogenous dose distribution with homogeneity index of 1.09±0.01 and 1.08±0.01 respectively when compared to 1.11±0.01 by 3DCRT (p=0.001 and 0.0001, respectively). D 2 (dose received by 2% of the tumour volume), a measure of maximum dose was greater in 3DCRT. While dose to the critical organs was considerably less in both two field IMRT and 3DCRT than in multiple field IMRT, two field IMRT achieved lowest doses. Moreover, there was a substantial increase in the Monitor Units (MUs) for multiple field IMRT when compared with the other two techniques. Conclusion: Two field IMRT have the features intermediate of 3DCRT and multiple field IMRT. The two field IMRT is on the beneficial side with homogenous dose distribution in the target and less dose to the critical organs. INTRODUCTION Breast cancer is the most common cancer among women worldwide and constitutes a significant burden even in under- developed countries with estimate suggesting that 60% of breast cancer deaths are from socioeconomically poor regions [1]. The stages of breast cancer can range from early, curable to metastatic breast cancer. Breast Conserving Surgery is becoming a preferred choice of treatment for breast cancer patients, especially in their early stages. It is less expensive and does not alter the social life of the woman as compared to Modified Radical Mastectomy. However, the outcome for survival and incidence of contralateral breast cancer is the same for both the surgeries [2]. Radiation Therapy finds its stand in the course of treatment and comes with a variety of treatment techniques due to the advancement in linear accelerators. The objective of radiotherapy is to provide a therapeutic dose to a distinct target while minimising the dose to adjacent normal tissues and critical organs. Achieving dose homogeneity in the breast is very important as it can help in reducing the late adverse effect. Changes in breast appearance have been found to be statistically higher in patients with more dose heterogeneity in the breast [3]. The 3DCRT is based on 3D anatomic information and uses dose coverage that will conform to the target volume as much as possible with minimum possible dose to normal tissue [4]. Often wedges or compensators are used to alter the intensity profile to offset contour irregularities. The 3DCRT method is simplistic and superior in terms of low-dose volume, integral dose and treatment time [5]. In IMRT, non-uniform fluence is delivered to optimise the composite dose distribution [4]. Optimal fluence profiles for a given set of beam directions are determined through inverse planning. This technique reduces maximum dose and improves conformity and homogeneity of the target volumes [6,7]. But, there is an increased risk almost by double for the secondary malignancies by the multiple field IMRT [5,8]. As there is an upturn in the survivors of breast cancer patients in the recent past, secondary malignancies and the long-term radiation induced toxicities in the heart and lungs are of concern [9]. This study aimed to compare three different radiotherapy techniques – 3DCRT, two field IMRT and multiple field IMRT in the treatment of Carcinoma Breast. MATERIALS AND METHODS This retrospective, dosimetric study was done in the Department of Radiotherapy and Oncology during the period January-August 2016. Ten female breast cancer patients who were previously treated with whole breast radiation after Breast Conservative Surgery (BCS) were included in this study. After getting the ethical committee approval and written informed consent of the patients, the planning Computed Tomography (CT) images of these patients were used to generate three different radiotherapy plans for the Keywords: Breast cancer, Conformal radiotherapy, Conformity index, Inverse planning