Monitoring of Disease in Patients Receiving 177LU-PSMA-617 Therapy in Routine Practice.

INTRODUCTION

177Lu-PSMA-617 (LuPSMA) is a radiopharmaceutical approved for the treatment of metastatic castration resistant prostate cancer (mCRPC). Consensus guidelines recommend multimodal disease monitoring during LuPSMA therapy, but there are no definitive recommendations regarding frequency and modality of imaging. Here, we sought to describe patterns in imaging utilization during LuPSMA therapy.

PATIENTS AND

METHODS

mCRPC patients treated with ≥ 2 cycles of LuPSMA between June 2022 and April 2024 were identified. Demographic, clinical, and imaging data were extracted from the medical record. Competing risks regressions were used to assess the association between clinical characteristics and receipt of restaging scans. Cox regression models and Kapan-Meier curves were used to describe the association between PSA50 response and overall survival.

RESULTS

One hundred eighty-four patients were eligible. 80 (44%), 63 (34%), and 21 (11%) patients underwent at least 1 CT/MRI/bone scan, prostate-specific membrane antigen-positron emission tomography/CT, and single-photon emission computed tomography-CT, respectively, during therapy; 20% of patients did not undergo any imaging during therapy. Among the patients who received restaging scans prior to therapy discontinuation for disease progression, 4/41 (10%) patients had radiographic disease progression in the absence of PSA progression.

CONCLUSION

There was marked heterogeneity in the use of imaging for disease monitoring during LuPSMA therapy 10% of patients experienced radiographic disease progression in the absence of PSA progression. PSA alone may be insufficient as a marker of disease response, and radiographic assessment remains an important part of disease monitoring in patients receiving LuPSMA.