A comparative study of RapidArc and intensity-modulated radiotherapy plan quality for cervical cancer treatment

ABSTRACT

Background: RapidArc therapy, a complex form of intensity-modulated radiotherapy (IMRT), is now widely used to treat cancer patients. Aims: This study aimed to investigate and compare the plan quality of IMRT and RapidArc techniques using various dosimetric indices to find the better treatment modality for treating patients with cervix cancer. Materials and Methods: Thirteen cervical cancer patients treated with IMRT were selected for analysis and original plans were subsequently re-optimized using the RapidArc technique. Plans were generated such that dose of 5000 cGy was delivered in 25 equal fractions. Inverse planning was done by Eclipse (Varian Medical Systems, Palo Alto, CA) treatment planning system for 15 MV photon beams from computed tomographic data. Double arcs were used for RapidArc plans. Quality of treatment plans was evaluated by calculating conformity index (CI), homogeneity index (HI), gradient index (GI), coverage, and unified dosimetry index (UDI) for each plan. Results and Conclusion: RapidArc resulted in better planning target volume (PTV) coverage as is evident from its superior conformation number, coverage, CI, HI, GI, and UDI. Regarding organs at risk (OARs), RapidArc plans exhibit superior organ sparing as is evident from integral dose comparison. Difference between both techniques was determined by statistical analysis. For all cases under study, modest differences between IMRT and RapidArc treatment were observed. RapidArc-based treatment planning is safer with similar planning goals compared to the standard fixed IMRT technique. This study clearly demonstrated that favorable dose distribution in PTV and OARs was achieved using RapidArc technique, and hence, the risk of damage to normal tissues is reduced.