Comparison of pelvic lymph node coverage in conventional radiotherapy based on boney landmarks versus contouring radiotherapy in cervical cancer patients

Aim: We aimed to compare pelvic lymph nodes coverage in Digital Reconstructed Radiography (DRR) based on bony landmarks and 3D planning based on contouring in external beam radiation of cervical cancer patients. Material and Methods: The study was carried out on 43 cervical cancer patients who were referred to Cancer Institute of Iran. We used RT Dose Plan software available in our department to define the treatment plan and field sizes. Images of patients were transported to RT dose plan software for planning. The Box treatment field (4 perpendicular fields) with or without additional brachytherapy was considered. The Dose Volume Histogram (DVH) and isodose curves were surveyed for acceptable tumour coverage. The study participants were assigned to two types of planning including planning based on anatomical markers (Conventional, DRR) and planning by considering the actual position of lymph nodes based on CT simulation images (CT). Results: The mean age of participants was 51 years. In the AP/PA field, the mean difference of superior, right, and left lateral borders was -2.31, -0.29, and -0.029, respectively. On the other hand, the mean difference of inferior border was estimated 1.87. Further, in the lateral field, the mean difference of DDR and CT approaches for anterior and posterior borders was 0.89 and 0.164, respectively. Conclusion: It seems CT simulation and use of contouring provide a better vision to pelvic lymph nodes and leads to wider coverage through reducing the possibility of ignoring treated areas. Nevertheless, more studies are required.