Interim PSMA PET/CT During 177Lu-PSMA Treatment in mCRPC

A study found that interim staging using PSMA-PET/CT and response classification by Response Evaluation Criteria In PSMA-imaging (RECIP) had prognostic value in men with metastatic castration-resistant prostate cancer (mCRPC) during 177Lu-PSMA treatment. The results were presented during the 2021 ASCO Annual Meeting.

The retrospective study comprised 124 men with mCRPC who underwent 177Lu-PSMA treatment and received PSMA-PET/CT at baseline (bPET) and after two cycles of treatment (iPET). Overall survival (OS) was the primary endpoint.

Median OS was 13.5 months. Seventy-three men presented at least one new lesion on iPET, which correlated with poor OS (hazard ratio [HR], 2.23; 95% confidence interval [CI], 1.51-3.28; P<0.001). Per the current data, the study authors defined partial response (PSMA-PR) as “a decline ≥20% in PSMA-positive tumor volume (PSMA-VOL) and no appearance of new lesions.” Progressive disease (PSMA-PD) was defined as “an increase ≥20% in PSMA-VOL and appearance of new lesions,” while stable disease (PSMA-SD) was defined as “any condition but not PSMA-PR or PSMA-PD.”

There were 41 men with PSMA-PD, 47 with PSMA-SD, and 36 with PSMA-PR. The PSMA-PD group had much poorer OS than the PSMA-SD group (HR, 2.52; 95% CI, 1.61-3.93; P<0.001) and the PSMA-PR group (HR, 4.16; 95% CI, 2.54-6.78; P<0.001).

“Interim staging using PSMA-PET/CT and response classification by RECIP is prognostic for survival of men with mCRPC treated with 177Lu-PSMA. Validation of these findings in clinical trials is warranted,” the study authors wrote in their conclusion.