Author: Shaheen Dewji, Emmanuel Mate-Kole, Sergio F Ruiz, Chris C. Wang 👨🔬
Affiliation: Georgia Institute of Technology, Nuclear and Radiological Engineering and Medical Physics Programs, Georgia Institute of Technology 🌍
Purpose: Extravasations are clinical events when a substance is administered intravenously and the fluid starts to leak into surrounding tissue instead of the target vessel. In the case of radiopharmaceutical extravasation, such occurrences become a health concern for patients because of the potential accumulation of radiation dose at the extravasation site. This study focuses on time-dependent dose estimations uniquely harnessing biokinetic modeling of radiopharmaceutical extravasations for metastatic castration-resistant prostate cancer patients being treated with Lu-177-PSMA therapy with the objective of determining the extent of any residual dose from potential radiotoxicity.
Methods: Extravasation is modeled through a biokinetic compartment framework, where an extravasation compartment is appended to the previously published model for Lu-177-PSMA and further modified to include the lymphatic system. This extravasation compartment is meant to represent the interstitial tissue and skin site where Lu-177-PSMA is administered, incorporating a biokinetic transfer rate for the extravasation compartment informed by the biological clearance of Lu-177 as stated in the model. The internal dose at the extravasation site was calculated using the MIRD method for injected activities of 3 GBq and 6 GBq.
Results: The absorbed doses at the extravasation site corresponding to 3 GBq and 6 GBq of the injected activities were 7..05 Gy and 14.09 Gy, respectively. Modeling results suggest that the doses calculated from extravasation are of concern and exceed the NRC dose limit for radiation exposure.
Conclusion: This study evaluates scenarios of extravasation in patients being treated with Lu-177-PSMA therapy, demonstrating that under the modeled conditions and assumptions, can produce doses of concern. Further work is required to account for a more precise lymphatic and metabolic circulation of the drug in the case of these radiopharmaceutical extravasations.