Introduction:

Results from the VISION trial (NCT03511664) led to the approval of lutetium-177 (177Lu)–PSMA-617 for the treatment of metastatic castration-resistant prostate cancer (mCRPC). This trial excluded patients with baseline cytopenias, thus safety in this frequently encountered patient population is unknown. We aimed to use real-world data to describe the tolerability of radioligand therapy in those with poorer bone marrow reserve.

Methods:

We retrospectively reviewed the records of all patients, who received a first dose of 177Lu–PSMA-617 at Mayo Clinic in the interval of April 26, 2022, to December 1, 2022.  Patients were categorized as having poor marrow reserve on the basis of pre-treatment hematologic parameters, including: (1) an anemia cohort with hemoglobin (Hg) less than 9 g/dL, (2) a thrombocytopenia cohort with platelets (Plt) less than 100 x 10⁹/L, (3) a leukopenia cohort with white blood cell count (WBC) less than 2.5 x 10⁹/L, and (4) a multiple cytopenia cohort.  These were exclusionary parameters from the VISION trial.  Longitudinal laboratory data and clinical outcomes were collected and analyzed using descriptive statistics.  

Results:

We identified 273 patients who received one or more doses of 177Lu, including 33(12%) with at least one baseline cytopenia prior to their first cycle of treatment.  There were 25(76%) patients with anemia, 4(12%) with thrombocytopenia, 2(6%) with leukopenia, and 2(6%) with multiple cytopenias.  The median number of cycles received is 4, including 21(64%) who are still receiving therapy and 12(36%) who have permanently discontinued treatment.  Median longitudinal changes in blood counts for anemia cohort are presented in Table 1.  Reasons for treatment discontinuation include: toxicity(n=5), disease progression(n=4), or death(n=8).  Among the 9 patients who stopped 177Lu for toxicity or disease progression, 5 subsequently also died. Dose reductions or treatment delays for worsening myelosuppression were utilized in 8(24%) and 8(24%) patients, respectively.  Transfusions of packed red blood cells or platelets were required for 26(78%) patients.  A total of 16(48%) received care in the emergency department or were hospitalized.

Conclusion:

Treatment discontinuation for toxicity was rare among men with mCRPC and baseline cytopenias, while receiving 177Lu; however, these patients have an overall poor prognosis.

Funding: N/A