Deviation Between the Planned Dose and the in Vivo Dosimetry Results During Postoperative Irradiation in Patients With Uterine Cancer Depending on Anthropometric Data

Abstract

Topometry is an integral part of irradiation whose task is to repeat the position of the patient set by the simulator to repeat the PTV and the spatial relationship between the radiation field and the risk organs that were identified during planning. The dose distribution formulated in the plan is only an ideal model. There is some gap between the actual and planned dose distribution, especially in overweight patients. Objective: evaluate the effect of anthropometric data on the deviation between the planned dose and the results of dosimetry in vivo in patients with uterine cancer during postoperative irradiation. Materials and Methods. The authors analyzed the results of treatment of 110 patients with stage IB–II uterine cancer who were treated at the Department of Radiation Therapy of the Institute of Medical Radiology and Oncology of the National Academy of Medical Sciences of Ukraine from 2016 to 2019. The technique of classical fractionation was used with a single focal dose of 2.0 Gy 5 times a week, the total focal dose was 42.0–50.0 Gy. To assess the effect of the patient’s anthropometric data on the difference between the actual and calculated dose, the authors performed in vivo dosimetry after the first session and in the middle of the postoperative course of external beam radiation therapy. Results. Рatients with BSA < 1.92 m2, had the median relative deviation at the first session -4.12 %, after 20.0 Gy – 3.61 %, patients with BSA > 1.92 m2: -2.06 % and -1.55 % respectively. After 20 Gy 34.8 % of patients with BSA < 1.92 m2 there was an increase in deviation from the planned dose, 65.2 % a decrease, while in 56.1 % of patients with BSA > 1.92 m2 there was an increase, and in 43.9 % – its reduction. With increasing BMI, the actual dose received on the rectal mucosa in the tenth session of irradiation is approaching the calculated one. Conclusions. When irradiated on the ROKUS-AM device, we did not find a probable dependence of the influence of the constitutional features of patients between the received and planned radiation dose. When treated with a Clinac 600 C, only body weight and body mass index at the tenth irradiation session have a likely effect on the dose difference. Therefore, issues related to the individual approach to the treatment of uterine cancer, depending on anthropometric data is an urgent problem of modern radiotherapy. Key words: anthropometric data, obesity, radiation therapy, preradiation preparation, in vivo dosimetry, uterine cancer.