Predicting Outcomes With LuPSMA in Metastatic Castration-Resistant Prostate Cancer
Posted: Friday, August 27, 2021
Matthias Eiber, MD, of the Klinikum rechts der Isar, Munich, and colleagues conducted an international, multicenter, retrospective study to develop nomograms to predict outcomes after treatment with the radiolabeled small-molecule inhibitor lutetium-177 prostate-specific membrane antigen (LuPSMA) in patients with metastatic castration-resistant prostate cancer. Their results were published in The Lancet Oncology.
“Our findings validate PSMA-PET companion imaging as a gatekeeper for patient selection and as a quantitative prognostic biomarker,” the investigators remarked. “Our nomograms, integrated in an online risk calculator, can assist in clinical trial design and individual clinical decision making.”
A total of 270 patients who had received LuPSMA as part of one of two previous phase II trials or compassionate access programs at 6 hospitals and academic centers in Germany, the United States, and Australia were enrolled; they were divided into development (n = 196) and validation (n = 74) cohorts. Predictors included in the nomograms were the time since initial diagnosis, chemotherapy status, baseline hemoglobin concentration, and gallium 68 PSMA-11 PET/CT parameters (molecular imaging TNM classification and tumor burden). Model performance was assessed using Harrell’s concordance index (C index). Follow-up data were provided for a median of 21.5 months.
The C index of the overall survival model was 0.71; at internal (0.71) and external (0.72) validation, similar C indices were achieved. In the prostate-specific antigen (PSA) progression-free survival model, the C index was 0.70; the C indices were similar at internal (0.70) and external (0.71) validation. The investigators noted that both the overall and PSA progression-free survival models were adequately calibrated; their predictions seemed to correlate with the observed outcome. In the validation cohort, low-risk patients seemed to experience a significantly longer duration of overall (24.9 vs. 7.4 months; P < .0001) and PSA progression-free (6.6 vs. 2.5 months; P = .022) survival than high-risk patients.
Disclosure: For full disclosures of the study authors, visit thelancet.com.