Monte Carlo-based Volumetric Arc Radiation Therapy vs. Helical Tomotherapy in Terms of Tumor Control Probability and Normal Tissue Complication Probability for Endometrial Cancers

Objective: This study aimed to compare the effectiveness and to plan parameters of the Monte Carlo (MC)-based volumetric arc radiation therapy (VMAT) plan, which was devised using the equivalent uniform dose concept for endometrial cancers, to the dose volume (DV)-based helical tomotherapy (HT) plan. Additionally, both approaches were evaluated in terms of tumor control probability (TCP) and normal tissue complication probability (NTCP).
Material and Methods: The study comprised ten patients diagnosed with endometrial cancer, and treated with radixact tomotherapy unit. The target volumes (PTV) and organs at risks (OARs) were contoured through an accuracy planning system. All plans were devised to receive a total of 50.4 Gy in 28 fractions with the fractional dose to be 1.8 Gy for patient treatment. Monaco 5.51 planning system hosted all planning computed tomography images to devise MC-based VMAT plans. Both plans were analyzed in terms of TCP and NTCP.
Results: DV-HT plans (CI: 1.1) came with the more conformal plan while the difference between both approaches was <1% for HI. Based on the results of the analyses, no statistical difference between DV-HT plan of MC-VMAT for the dose values of 2%, 30%, and 40% of rectal volume (p>0.05) was observed. The same results were obtained for the dose values of 2% and 30% of the bladder volume (p>0.05). The D5% of the femoral heads were 7 Gy which is < MC-VMAT plan compared to DV-HT plan. The NTCP values of all OARs were <1% in both approaches.
Conclusion: Statistically, similar results were obtained in MC-VMAT and DV-HT plans for OAR’s doses when the treatment dose was given to PTV. Both approaches had no significant difference for NTCP statistically; however, the possibility of bone marrow complications to be investigated as well was concluded, so as to evaluate hematological toxicity.