Modeling of Integral Radiobiological Criteria for Simultaneous Irradiation of Multiple Targets with Different Absorbed Total Doses

Abstract

Purpose: The paper is devoted to the comparison of simultaneous (SIB) and sequential (SEQ) radiation therapy of primary-multiple tumors with different absorbed total doses based on the modeling of integral radiobiological criteria. The research is aimed at optimization of treatment of rare primary-multiple tumors, development of optimal approaches based on the analysis of the effectiveness of different irradiation options. Material and methods: This research considers a system of primary-multiple targets, using a gynecologic tumor including vagina (adenosquamous carcinoma), endometrium (moderately differentiated adenocarcinoma with foci of squamous metaplasia), and lymph nodes as an example, to which certain equivalent total doses of irradiation must be delivered (EQD2>=74.8 Gy for vagina, EQD2>=85 Gy for endometrium). Different scenarios of two-stage and one-stage irradiation, including different combinations and doses for each target, are studied in the simulation. Results: Comparison of treatment plans for the triple target system shows that, performing sequential radiotherapy SEQ is characterized by higher levels of equivalent total dose delivered to the target volumes taking into account the total irradiation time and, consequently, to the critical organ volumes, especially in the rectum and sigmoid colon. In case of simultaneous irradiation SIB, the duration of treatment is five weeks instead of seven weeks, which reduces the value of the equivalent total dose to the target by 7-10 Gy. The value of the absorbed single dose delivered to the target volume is up to 3 Gy, which can be attributed to moderate hypofractionation. Levels of radiation exposure for critical organs in this case are much lower than when two-stage irradiation is used. Conclusion: Simultaneous integrated boost radiation therapy allows a significant reduction in radiation exposure to critical organs compared to sequential radiation therapy (reduction to single systems).