Dosimetry Impact of Absorbed Dose to Tumor and Organ at Risk on Mixed Beam Planning for Cervical Cancer

Purpose: The purpose of this study is to determine the dosimetric impact of mixed energy plans for Carcinoma Cervix in the form of 3DCRT. Plans were differentiated based on PTV, Rt femoral head, Lt femoral Head, Rectum, Urinary Bladder, Bowel-Bag. Methods and Materials: A cohort study of 20 cervix cases involving lymph nodes was selected for this study. They have previously been treated by a single oncologist at KYAMCH Cancer Center. For each cervix case we use single-energy plan (6 MV photon energy), single-energy plan (15 MV photon energy) and mixed photon energy plans (6 MV and 15 MV energy). First, we use single beam photon energy (6 MV & 15 MV) individually for both the primary and boost plan. Second, we use both 6 MV & 15 MV as mixed energy plan for both primary and boost plan, Prescription dose was 50 Gy 25 days per fractions for 20 cases. The coverage of the target was evaluated with the value of Mean Dose, Maximum Dose, V95% coverage for 98%. Result: The dose to rectum is higher in single energy photon plan of 15 MV than single energy photon plan 6 MV and mixed photon energy plan (6 MV and 15 MV mixed). The mean dose to Rt femoral head is higher in mixed energy plan than individual single photon energy plan but for Lt femoral head the mean dose is higher in 15 MV energy (single photon energy plan). The mean dose to urinary bladder is higher in 15 MV individual single photon energy plan than individual single photon energy plan 6 MV and mixed photon plan 6 MV and 15 MV. Bowel Bag dose at 195cc coverage, we get higher dose in mixed energy form (6 MV & 15 MV) than in individual 6 MV & 15 MV photon energy plans. PTV coverage for individual 6 MV photon beam 97.113% = 4607.33 cGy coverage for 15 MV individual single photon energy 97.97% = 4669.16 cGy and for mixed photon energy 6 MV and 15 MV 97.38% = 4641.66 cGy. Conclusion: The initial result from this pilot study we can suggest that the mixed beam planning of 3D CRT cervical cancer could minimize the dose to rectum and bladder but results in a higher dose to Rt femoral head and bowel bag dose.