Impact of IMRT- and VMAT technologies on selection of total dose of radiation therapy in patients with squamous cell carcinoma of anal canal

Abstract

Accurate determination of the tumor with the use of modern diagnostic methods which make the maximum exposure to the tumor and the identified affected lymph nodes possible lead to careful attitude to healthy tissues and critical structures. During the period 2000-2015 301 patients with squamous cell carcinoma of the anal canal stage T1-4N0-3M0-1 completed complex treatment which consisted of radiation therapy in a conventional or conformal mode, including the use of modern technologies - radiation therapy with intensity modulation - IMRT and arch volume-modulated radiation therapy - VMAT. The use of IMRT andVMAT in comparison with conformal radiation therapy allowed to reduce the frequency of unplanned interruptions up to 48 % (p = 0.005), which led to increase in 5-year rates of local regional control - 83.7 % compared with the group where the interruption was applied - 74.2 % (p = 0.049); also increased the frequency of complete responses in the range of the total dose of 50-54 Gy to 28.5 %, 56-58 Gy to 44.3 % and 60-64 Gy to 26.1 %. The achievement of a complete response led to a significant increase in the 92.1 % 5-year locoregional control compared to the group with the absence of a complete response - 76.5 % (p = 0.001). Modern conservative treatment is based on continuous radiation exposure with the absence of intervals between courses, which is the radiobiologically considered the most effective treatment regimen.