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.
ВступРак тіла матки (РТМ) становить 4,8 % серед злоякісних пухлин у жінок і займає 6-те місце в структурі захворюваності жінок на злоякісні пухлини у світі після раку молочної залози, колоректального раку, раку легенів, шийки матки [1]. Серед пухлин жіночих статевих органів РТМ зустрічається найчастіше у розвинених країнах [2], але цей показник може різнитися в розвинених країнах та в тих, що розвиваються, а також у межах окремих країн [3, 4]. Так в Україні у 2017 році рівень захворюваності на РТМ сягнув 19,7 % на 100 000 жінок [1]. Більшість випадків захворювання діагностується на стадії локалізованого процесу, а саме в I, II стадії -74,7 %, при цьому показники 5-річної виживаності суттєво вищі та при І стадії сягають 90 %, а при II стадії -83 % [5].Тактика лікування хворих на РТМ стандартна, залежить від поширеності процесу, віку хворих, наявності супутніх захворювань, проводиться згідно з локальними та міжнародними стандартами. У більшості клінічних випадків перевага віддається комбінованому методу лікування, який складаєть-
Relevance: Radiotherapy is the standard post-surgery treatment in patients with uterine cancer. However, radiotherapy affects 90.0–100.0% of the volume of risk organs. Information on the actual dose delivered to critical structures is needed to ensure the quality of radiotherapy. The purpose of this study was to determine the impact of the type of ionizing radiation on the dose load on the rectal mucosa using in vivo dosimetry. Results: At the first and tenth sessions of treatment using a cobalt apparatus, the in vivo dosimetry showed that the minimum value of the dose received during the tenth cycle was higher by 0.1 Gy. That is, the deviations from the planned dose were less at the same maximum values. Both the average value and the median during the tenth cycle were also moderately higher. The relative difference between the dose planned and received during the tenth cycle was higher than during the first cycle by an average of 1.12575%, with a median of 0.82214. When conducting radiotherapy using a linear accelerator, the average and median values were higher in the second measurement despite almost identical minimum and maximum values. The relative difference between the planned and received doses during the tenth cycle was higher than during the first cycle by an average of 0.55619%, with a median of 0.42948. Conclusion: The conducted study showed an intro- and interindividual variability of in vivo dosimetry results during radiotherapy of genital cancer patients. In vivo dosimetric control showed that the relative difference between the doses calculated and received by the rectal mucosa upon reaching of 20.0 Gy dose in comparison to the first irradiation cycle were twice higher on the ROCUS-AM cobalt apparatus vs. the Clinac 600 C linear accelerator. The data obtained during the investigation indicates the need to develop innovative approaches to topometric preparation of genital cancer patients and to continue their dosimetric monitoring to establish the causes of discrepancies in the results.
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