Patient external dose rate after ¹⁷⁷Lu-DOTATATE therapy: factors affecting its decrease and predictive value.

Area of Science:

• Nuclear Medicine
• Radiopharmacology
• Oncology

Background:

• Peptide receptor radionuclide therapy (PRRT) using 177Lu-DOTATATE involves external radiation exposure from patients.
• Assessing radiation dose rates is crucial for determining safe patient discharge protocols post-PRRT.

Purpose of the Study:

• To determine the equivalent dose rate at 1 meter (EDR-1m) after 177Lu-DOTATATE administration.
• To predict which patients can be safely discharged approximately 3 hours post-PRRT, enabling outpatient or day-patient treatment.

Main Methods:

• Prospective observational study (PREELU) measuring EDR-1m at the sternum and pelvis.
• Measurements were taken sequentially for at least 180 minutes after 177Lu-DOTATATE infusion in 24 patients with metastatic neuroendocrine tumors.

Main Results:

• 180 minutes post-PRRT, EDR-1m was <40 µSv/h in all patients and <25 µSv/h in 64%.
• Patients with creatinine clearance >96 mL/min/1.73m² were 90% likely to have EDR-1m <25 µSv/h within 180 minutes.
• EDR-1m <25 µSv/h at 180 minutes during the first PRRT cycle predicted an 88% likelihood of survival at two years.

Conclusions:

• All patients met the <40 µSv/h discharge criterion at 3 hours post-PRRT.
• A stricter <25 µSv/h criterion would necessitate extended stays for about one-third of treatments, predictable by creatinine clearance.
• Early EDR-1m measurements show prognostic value for long-term survival, warranting further investigation.