[¹⁷⁷Lu]Lu-PSMA-617 Therapy in a Patient with Chronic Kidney Disease

Clinical Status of the Patient

A 63-y-old patient with metastatic castration-resistant prostate cancer was referred to our hospital for [¹⁷⁷Lu]Lu-PSMA-617 RLT after all available options of first- and second-line treatments had been exhausted.

We established the indication for RLT on the basis of the high binding of the PSMA ligand [¹⁸F]F-PSMA-1007 in the metastases. During the 4 y before RLT, the patient had received hemodialysis 3 times per week because of CKD with autosomal-dominant polycystic kidney disease. Supplemental Table 1 reports the renal-function data before each RLT cycle (supplemental materials are available at http://jnm.snmjournals.org).

RLT Procedure with Hemodialysis

The patient underwent 6 RLT cycles at our department between October 2021 and August 2022. In each cycle, the patient received between 7.71 and 8.07 GBq of [¹⁷⁷Lu]Lu-PSMA-617 (cumulative activity, 47.3 GBq), which was administered by intravenous injection. He stayed in the therapy ward for approximately 72 h after each cycle.

During the first RLT cycle, the patient received 3 hemodialyses while in the therapy ward. In the subsequent cycles, the patient maintained his regular hemodialysis schedule, corresponding to 2 hemodialyses during each ward visit (Table 1). With no access to treated water for dialysis at our facility, we replaced regular dialysis sessions with hemodiafiltration sessions using a Prismaflex device (Baxter International Inc.). We compensated for the lower clearance with an increased treatment time of 6.2–7.6 h, resulting in a clearance time per volume of 0.9 (6). The dialysate volume ranged from 40.3 to 57.0 L (Table 1). To assess the ¹⁷⁷Lu clearance from the blood, we measured the radioactivity concentration in the blood samples collected at the beginning of every hemodialysis and before the patient was discharged from the clinic.

Dosimetry

We performed the dose calculation for the organs at risk with the voxel dosimetry application of Hermes (Hermes Medical Solutions) (7) using SPECT/CT images (Siemens Healthineers Intevo Bold; medium-energy collimator, 128 × 128 matrix; Siemens Healthineers xSPECT reconstruction) acquired at 1, 2, 3, and 10 d after injection for 30 min of scan time in each session. A nuclear medicine resident physician segmented the parotid gland, submandibular gland, left colic flexure, and right kidney on the dose maps obtained from Hermes.

Following previous work (8,9), we used blood sampling to estimate the red bone marrow (RM) radioactivity dose. We opted for a Bayesian fit of a single-exponential function to the data (Gaussian likelihood, Gaussian priors of 0.1 ± 0.025 h⁻¹ for a mean half-life and 0.89 ± 0.38 MBq/mL for the amplitude) to determine the time-integrated activity from which we performed the dose calculation according to previous data (8).

Radiation Protection

The therapy was conducted according to the standard radiation protection requirements for [¹⁷⁷Lu]Lu-PSMA-617 (10). While the nurse performed the hemodialysis, we monitored the whole-body effective dose with an electronic personal dosimeter to assess the additional radiation burden (11). We measured the dose rate of the patient before each discharge from the clinic and instructed him to follow radiation protection measures according to the Swiss regulations (www.bag.admin.ch/str-wegleitungen). Furthermore, we advised the personnel routinely performing the hemodialysis to follow standard radiation protection measures outside the therapy ward for 9 d after injection (use of disposable gloves and exclusion of pregnant women from performing the hemodialysis). We measured the residual activity in the dialysate at the beginning and at end of each hemodialysis with a calibrated γ-counter.