A Case Series of Dosimetric Comparison-VMAT (RapidArc), IMRT, 3DCRT for Extended Field Radiotherapy in Cervical Cancer

Purpose: To compare plans of 3DCRT, IMRT and VMAT (RapidArc) and evaluate them in different dosimetric aspects along with dose to organs at risk with each technique to determine the best treatment technique for Extended field RT in cervical cancer patients Material & Methods: We evaluated External Beam radiotherapy plans of 10 patients of FIGO 2018 stage rIIIC2 who received Extended Field Radiotherapy (EFRT) to primary site along with regional nodes-bilateral external, internal iliac lymph nodes, presacral and para-aortic lymph nodes. The dose prescribed for all patients was 50.4Gy/28 fractions at 180cGy/fraction. Few patients had received gross nodal boost following this, but for better comparison only the initial phase of 50.4Gy/28 fractions was considered. All patients were planned with 3DCRT, IMRT and RapidArc. We evaluated and compared these plans dosimetrically in terms of Homogeneity Index, Conformity Index, Target Volume Coverage, Gradient Index, Unified Dosimetry Index, Integral dose, Monitor units and Doses to Organs at risk such as Anorectum, Bladder, Bowel Bag, Bilateral Femoral Heads, Bilateral Kidneys and Bone Marrow. Results: Intensity modulated techniques RapidArc and IMRT significantly spared critical organs compared to 3DCRT. Between RapidArc and IMRT, the critical organ sparing was comparable, but RapidArc had better target coverage, lesser MU and lesser treatment time. All techniques had acceptable HI, CI, GI, UDI and whole body Integral dose. Conclusion: Intensity modulated techniques should be the standard for EFRT in cervical cancer. Both RapidArc and IMRT are acceptable techniques of treatment delivery although the former may be preferred if and when available.