Evaluation of Dose-Painting in the Dominant Intraprostatic Lesions by Radiobiological Parameters using ۶۸Ga- PSMA PET/CT

Background: Patients diagnosed with dominant intraprostatic lesions (DIL) may need radiation doses over than ۸۰ Gy. Dose-painting by contours (DPC) is a useful technique which helps the patients. Dose-painting approach need to be evaluated. Objective: To evaluate the DCP technique in the case of boosting the DILs by radiobiological parameters, tumor control probability (TCP), and normal tissue complication probability (NTCP) via PET/CT images traced by ۶۸Ga-PSMA.Material and Methods: In this analytical study, ۶۸Ga-PSMA PET/CT images were obtained from patients with DILs that were delineated using the Fuzzy c-mean (FCM) algorithm and thresholding methods. The protocol of therapy included two phases; at the first phase (ph۱), a total dose of ۷۲ Gy in ۳۶ fractions were delivered to the planning target volume (PTV۱); the seconds phase consisted of the application of variable doses to the PTV۲. Moreover, two concepts were also considered to calculate the TCP using the Zaider-Minerbo model. Results: The lowest volume in DILs belonged to the DIL۱ extracted by the FCM method. According to dose-volume parameters of the rectum and bladder, by the increase in the PTV dose higher than ۹۲ Gy, the amounts of rectum and bladder doses are increased. There was no difference between the TCPs of DILs at doses higher than ۸۶ Gy and ۱۰۰ Gy for ordinary and high clone density, respectively.  Conclusion: Consequently, our dose-painting approach for DILs, extracted by the FCM method via PET/CT images, can reduce the total dose for prostate radiation with ۱۰۰% tumor control and less normal tissue complications.