Designing the best treatment plan for patients with nasopharyngeal carcinoma treated with SIB-VMAT using the MONACO treatment planning system

Abstract

Author(s): Salam Abdulrazzaq Ibrahim Al-Rawi, Ahmed Alshewered*, Hassan Abouelenein, Haidar Hamza Alabdei, Awf Abdulrahman Sulaiman, Dalya Saad Al-Nuaimi, Mohamed El-Sayed El Nagdy and Magdy Mohammed Khalil

To select the best treatment plan in terms of quality, delivery time, and monitor units resulting from different planning scenarios with different arcs and segment widths for patients with nasopharyngeal carcinoma treated with the Simultaneous Integrated Boost-Volumetric Modulated Arc Therapy (SIB-VMAT) technique using the MONACO treatment planning system. A dosimetric comparison of eight VMAT phantom planning techniques was performed on 30 patients by changing the number of arcs and the minimum segment width, where the eight techniques were abbreviated as A (maximum number of arcs, minimum segment width in cm). Thus, the eight techniques were A1(1, 0.5), A2(1, 1), A3(1, 1.5), A4(1,2), A5(2, 0.5), A6(2, 1), A7(2, 1.5), and A8(2, 2). There was a significant difference in the dose delivered to the organs at risk among the eight plans. The best target coverage was for the A1 and A5 plans, and the rest did not meet the planning requirements in terms of target coverage. The treatment delivery time was significantly shorter for the A1 plan, and the monitor units were comparable between the A1 and A5 plans. The best target coverage was for the A1 plan followed by that for A5. The conformity, homogeneity, and dose gradient indices had the best values for the A5 plan. For the treatment of nasopharyngeal carcinoma with the VMAT technique, the optimized plan should be with a minimum segment width of 0.5 cm and a single or double arc. The treatment planning is infeasible for a minimum segment width bigger than 1 cm.

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