ABSTRACT
Spatially fractionated radiotherapy (SFRT) is one of the nonconventional radiotherapy techniques utilized to treat patients with advanced bulky tumors. This study was aimed to estimate the different dosimetric parameters of the SFRT technique and compare it to the three-dimension conformal radiotherapy (3D-CRT) of bulky pelvic tumors. 3D-CRT and SFRT were designed by the Monaco treatment planning system. Twelve bulky pelvic tumor cases were selected, a single fraction with a high dose 15Gy was used. Dosimetric parameters were calculated minimum dose (Dmin), mean dose (Dmean), and maximum dose(Dmax) (Gy) for organs at risk (OARs). Also, the dosimetric parameters were calculated of tumors, Dose near maximum (D2) Gy, mean dose (D50) Gy, Dose received by 95% volume (D95) Gy, and Dose near minimum (D98) Gy. SFRT achieves fewer doses for OARs were compared to 3D-CRT. In SFRT, where OARs in close to the tumors and shielding it by multi-leaf (MLCs) with thick (1 cm) leads to more effective than other techniques. Also, SFRT was at variance with 3D-CRT techniques for different cases of D2, D50, D95, and D98 ( Gy ) for the tumors. There are significant differences between the two methods for all OARs for Dmin, Dmean, and Dmax (Gy), also, D2, D50, D95, and D98 (Gy) for the tumors, p –values less than 0.05. Although SFRT plans noted less coverage tumor than 3D-CRT. However, the SFRT method kills tumor cells by indirectly radiating, abscopal effect, vascular damages, and immunomodulation reactions occur by radiobiological mechanisms in this method with 15 Gy. It could be concluded that SFRT achieves more sparing and fewer complications for OARs by limiting the volume of tissues being exposed to high doses of radiation when compared with 3D-CRT.