Comparative Dosimeteric Evaluation of Intensity Modulated Radiation Therapy versus Conventional Radiotherapy in Postoperative Radiotherapy of Breast Cancer

Aim: To dosimetrically compare and evaluate Intensity Modulated Radiation Therapy (IMRT) versus conventional five field radiotherapy (5FCRT) in postmastectomy radiotherapy (PMRT). Material and Methods: This study included 25 consecutive patients for PMRT. Target volumes (chest wall, axilla, supraclavicular regions [SCF]) and normal structures (lungs, heart, spinal cord, opposite breast) were delineated on the planning CT scans. For each patient, one IMRT and one 5FCRT plan were generated for 50 Gy and corresponding dose volume histograms were compared. Differences in means of each set of variables were tested for significance. Results: CTV and PTV of chest wall, IMC, axilla level l, ll, lll and SCF were evaluated by variables D98%,D2%, D50% V<95, V>105, V>107, homogeneity index (HI). Coverage of the PTV given chest wall was significantly better with IMRT than conventional. The HI was more with conventional 0.6+0.2, IMRT 0.1+0.1, p<0.001. PTV of axilla and SCF, D98% were better with IMRT than conventional. In IMRT HI was 0.1+0.1 while 0.4+0.2 conventional p<0.02. In lung V20 of the ipsilateral lung with IMRT was significantly lower than that of the conventional. In heart D33% by IMRT was 17.3 + 10.0 Gy and 33.2+11.3Gy in conventional (p<0.001). Mean dose received by opposite breast was 5.8 + 1.8 Gy by IMRT and 2.0+1.0Gy by conventional p<0.001. Conclusion: IMRT technique is superior to the conventional technique due to its better chest wall, axilla and SCF coverage. IMRT significantly reduced heart, lung and spinal cord doses as compared with conventional technique.