Can a low-energy photon beam be suitable for the treatment of cervical malignancies? A dosimetric analysis

Background: Radiotherapy to a patient with cervical cancer can be delivered by four-field “box technique” with a benefit of much less dose to intervening tissues along with a better and homogenous dose distribution at the target location. An important ingredient for a good radiotherapy planning is the choice of beam energy. The present study aims to investigate the feasibility of a 4 MV photon beam for the treatment of cervical cancers. Materials and Methods: A population of 20 patients, with carcinoma cervix, was included in the study. All the patients were planned for a prescribed dose of 45 Gy in 25 fractions. Results: Plans were evaluated for planning target volume and found better in terms of coverage and hot spots using 6 MV. The homogeneity index (HI) was 1.1 for both the energies. Similarly, conformity index (CI) was 2.0 depending on the method used for 4 MV and 6 MV photons. Although the HI and CI were comparable for both the plans, yet it seems significantly better for 6 MV. This indicates that spillage in 6 MV plans is lesser as compare to 4 MV. The present study reveals that there is a significant reduction in total monitor units in the plans with 6 MV photon beams, leading to fewer chances of secondary malignancies. Conclusion: A 6 MV photon beam has some proven mileage over 4 MV in terms of target coverage, dose homogeneity, and conformity and remains the best suitable photon energy for the treatment of cervical malignancies.