Extravasation Frequency of [177Lu]Lu-DOTATATE: Insights and Implications Derived from 1,314 Cycles of Treated Patients-A Single-Site Analysis.

Extravasation of radiopharmaceuticals raises potential concerns, including adverse tissue reactions and reduction in both quantitative accuracy and therapeutic efficacy. This study presents a single-center experience reviewing extravasation events during [¹⁷⁷Lu]Lu-DOTATATE administration in peptide receptor radionuclide therapy, assessing their frequency, impact on patient care, and dosimetric effects. Methods: [¹⁷⁷Lu]Lu-DOTATATE was administered intravenously to outpatients following standard peptide receptor radionuclide therapy protocols. Whole-body planar imaging was performed 3-4 h after injection to confirm administration and assess extravasation, indicated by focal increased uptake at the infusion site. Qualitative image reviews by nuclear medicine physicians or technologists flagged potential extravasations. For these cases, regions of interest were delineated over the infused and contralateral arm and on the thighs. Extravasated activity was quantified relative to injected and whole-body activity. Absorbed dose calculations were performed using the MIRD formalism, assuming a monoexponential clearance model and accounting for varying extravasate volumes, with infiltration depths ranging from 2 to 7 mm. Statistical analyses compared retained activity and dosimetric parameters between extravasation and control groups. Results: Among 1,314 administrations in 365 outpatients, 14 cases (1.1%) had increased uptake at the infusion site, suggesting extravasation. The maximum radiopharmaceutical retention at the infused site was less than 1% of total injected activity and less than 2.1% whole-body activity (accounting for bladder voiding). The corresponding extravasated activity related to administered activity was 0.07% and 0.01% in the extravasation and control groups, respectively (P < 0.001). The extravasation group had higher absorbed dose estimates at the infusion site than did the control group (median, 0.53 Gy [range, 0.12-1.23 Gy] vs. 0.32 Gy [range, 0.17-0.71 Gy]; P = 0.3), with a significantly higher median extravasated dose (0.14 Gy [range, 0.03-0.67 Gy] vs. 0.02 Gy [range, 0.0-0.19 Gy]; P < 0.001). We did not observe any radiogenic tissue reactions. Conclusion: Extravasation during [¹⁷⁷Lu]Lu-DOTATATE therapy was rare and resulted in minimal dosimetric consequences, with absorbed doses at the infusion site well below the thresholds for deterministic effects and soft-tissue necrosis. These findings indicate that extravasation had a negligible impact on treatment efficacy and patient safety in this patient cohort, reinforcing the safety of [¹⁷⁷Lu]Lu-DOTATATE administration protocols and emphasizing the low clinical risk associated with radiopharmaceutical extravasation during therapy.