Improved prediction of haematological toxicity during 177Lu Lu-DOTA-TATE therapy by optimising serial SPECT-CT red marrow dosimetry

Abstract

Aim/Introduction: This research compared red marrow absorbed dose estimations following Peptide Receptor Radionuclide Therapy (3D Image Based (IB) versus Blood Based (BB) methods), and dose correlations with haematological toxicity. Materials and Methods: Data were acquired during cycle 1 of [177Lu]Lu-DOTA-TATE therapy for a cohort of PRRT patients. Red marrow dosimetry was performed using BB methods and IB methods using serial SPECT/CT methods, with dose uncertainties estimated. The effect on total dose (due to self & cross-irradiation) was assessed for two different cross-irradiation models (simplistic versus realistic). The strength and significance of the correlation between dose and post therapy platelet toxicity were assessed for each dosimetry method. The effect of exposure to prior treatments on dose toxicity correlations was also assessed. Results: Early results indicate that IB methods delivered significantly higher red marrow absorbed doses than BB methods (mean increase of a factor of 3 when cross-irradiation was included). Choice of cross-irradiation model had a significant impact on total dose magnitude for both BB and IB techniques. Dose response analysis of these initial results indicate that the simplistic cross-irradiation model gave the strongest and most significant dose - toxicity correlations for both IB and BB methods. The most realistic activity distribution model produced significant correlations only with IB methods for therapy naïve patients. Conclusion: Red marrow absorbed doses measured from serial SPECT were significantly higher than those from serial blood measurements. IB absorbed doses produced stronger and more significant correlations for therapy naïve patients than BB absorbed doses