A Monte Carlo Study of Absorbed Dose From <sup>177</sup>Lu and <sup>90</sup>Y -DOTATATE in XCAT Phantoms With Different Body Mass Indices

Abstract

PurposeRecently introduced radiopharmaceutical radiolabeled peptide has attracted growing interests for neuroendocrine cancer therapy. We aim to calculate S-values of Lu-177, In-111 and Y-90 in different BMIs of XCAT male phantoms for pre-estimation of absorbed dose in critical target organs using Monte Carlo simulation to see the extent of difference.Materials and methodsSeven BMIs of XCAT male phantoms were generated. Spline, bladder, kidneys, and liver were chosen as the source organs and the S- values were calculated in interested target organs. GATE code was used to perform dosimetry calculations for 20 MBq activity of both agents.ResultsThe S-values in both self-absorptions and target organs were dramatically lower for 177 Lu -DOTATATE compared to 90 Y-DOTATATE. The highest difference between the absorption in kidneys is for BMI of 28.3. The highest S-value in bladder from bladder is 0.01 mGy/MBq.s in BMI of 34.5 for 177 Lu-DOTATATE, whereas it is 0.0049 mGy/MBq.s in BMIs of 34.5 for 90Y-DOTATATEConclusionOur results showed that the absorbed dose in critical organs falls down dramatically when 177Lu-DOTATATE is employed instead of 90Y-DOTATATE. Although absorbed dose in target cells is higher for 90Y-DOTATET, the lower absorbed dose in patient critical organs may be another reason to put 177Lu-DOTATATE in superiority for neuroendocrine cancer therapy.