Evaluating the influence of 6MV and 10MV photon beams on cervical cancer volumetric-modulated arc therapy plans

BACKGROUND: Cervical cancer is a common gynecological cancer among women worldwide. OBJECTIVE: To determine the effects of 6 MV and 10 MV volumetric-modulated arc therapy (VMAT) photon beams on the target volume (TV) planning and critical organs in cases of cervical cancer. METHODS: Fifty patients with carcinoma of the cervix who underwent radiotherapy were selected. The transverse diameter (T) of the cross section of the upper edge of the sacroiliac joint on computerized tomography (CT) images of the patients was measured, and the mean value was calculated as 34 cm. All patients were divided into two groups: Group A (T < 34 cm) and Group B (T > 34 cm). The VMAT plans were generated using 6 MV and 10 MV plans separately. The prescription dose was 47.5 Gy, and the daily dose was 1.9 Gy. RESULTS: In Group A, the planning target volume (PTV) dose assessment parameters of 6 MV and 10 MV plans and their homogeneity and conformity indices were not statistically significantly different. A significant difference was observed between the 6 MV and 10 MV plans for the PTV dose assessment parameters and the homogeneity index of the plans for Group B. The monitor units (MUs) of the 10 MV plans were lower than in the 6 MV plans in both Groups A and B, and the difference was statistically significant. The assessment parameter V-40 Gy of both the rectum and bladder in the 6 MV plans was smaller than the corresponding parameter in the 10 MV plans in Group A; in Group B, the assessment parameter V-50 Gy of the rectum in the 10 MV plans was smaller than in the 6 MV plans. CONCLUSION: When T < 34 cm, 6 MV energy is more suitable for the external irradiation of cervical cancer. When T > 34 cm, 10 MV energy is more suitable for cervical cancer radiotherapy. Therefore, 10 MV should be considered for patients with a large abdominal size.