Long-term adverse events (AE) in patients with metastatic castration-resistant prostate cancer (mCRPC) receiving prostate-specific membrane antigen (PSMA)-based targeted radionuclide therapy (TRT).

Abstract

5055 Background: PSMA-TRT is a promising investigational treatment for patients with mCRPC. Expected short-term toxicities associated with PSMA-TRT include dose-dependent myelosuppression and xerostomia. However, there is a lack of information regarding long-term effects of PSMA-TRT on marrow, renal, and liver function. Additionally, potential organ dose limits for radiation are derived from studies of external beam radiation, which may not be applicable to TRT. Methods: Men treated on prospective clinical trials of PSMA-TRT, from 2003 through 2020 with at least six months of follow-up were included. Variables included treatment, co-morbidities, baseline and most recent renal, liver, and marrow function, along with respective short-term ( < 6 months) and long-term toxicities. AEs were graded using CTCAE version 5 and attribution was assessed with most recent clinical follow up. Multivariable logistic regression was used to control for type of TRT, comorbidities, and subsequent therapies. Results: 71 (59.7%) patients who received 177Lu-J591, 30 (25.2%) 177Lu-PSMA-617, 11 (9.2%) 225Ac-J591, and 7 (5.9%) 90Y-J591 were included, with median follow up 18 months (range 6-133). Long-term (most recent) laboratory values and AEs are summarized in the table. A majority of AEs were attributed to alternate etiologies. 5 of 14 cases of grade (Gr) ≥2 creatinine increase, 3 of 36 cases of Gr ≥2 platelets, 2 of 14 cases of Gr ≥2 bilirubin, 1 of 15 cases of Gr ≥2 AST increase, and 1 of 5 cases of Gr ≥2 ALT increase were deemed possibly related to PSMA-TRT. Only two Gr ≥3 AEs were attributed to possibly being related to PSMA-TRT: one case of Gr 4 creatinine elevation and one case of Gr 3 ALT elevation. On multivariable analysis, alpha-TRT was associated with hepatic AEs (OR 4.38, p = 0.047), and there was a trend towards higher Charlson Comorbidity scores associating with hematologic AEs (OR 1.27, p = 0.095). Conclusions: This is the largest analysis to-date of long-term AEs in patients who have received PSMA-TRT. Long-term effects on renal, liver, and marrow function are infrequent.[Table: see text]