Third-line Life-prolonging Drug Treatment in a Real-world Metastatic Castration-resistant Prostate Cancer Population: Results from the Dutch Castration-resistant Prostate Cancer Registry

Abstract

BackgroundEvidence concerning third-line life-prolonging drugs (LPDs) in the treatment of metastatic castration-resistant prostate cancer (mCRPC) patients is incomplete. ObjectiveTo evaluate third-line LPD outcomes in a real-world cohort of mCRPC patients, identify variables associated with overall survival (OS), and establish a prognostic model. Design, setting, and participantsPatients with mCRPC who were progressive on second-line LPD before July 1, 2017 were retrospectively identified from the Dutch Castration-resistant Prostate Cancer Registry (CAPRI) and followed until December 31, 2017. Outcome measurements and statistical analysisAssociation of potential risk factors with OS was tested by Cox proportional hazard models after multiple imputation of missing baseline characteristics. A predictive score was computed from the regression coefficient and used to classify patients into risk groups. Results and limitationsOf 1011 mCRPC patients progressive on second-line LPD, 602 (60%) received third-line LPD. Patients receiving third-line LPD had a more favorable prognostic profile at baseline and longer median OS than patients with best supportive care (10.4 vs 2.4 mo, p < 0.001). Eastern Cooperative Oncology Group performance status 1 and ≥2 (hazard ratio [HR] 1.51, p < 0.007 and HR 3.08, p < 0.001, respectively), opioid use (HR 1.55, p = 0.019), visceral metastases (HR 2.09, p < 0.001), hemoglobin <7 mmol/l (HR 1.44, p < 0.002), prostate-specific antigen ≥130 μg/l (HR 1.48, p = 0.001), alkaline phosphatase ≥170 U/l (HR 1.52, p < 0.001), and lactate dehydrogenase ≥250 U/l (HR 1.44; p = 0.015) were associated with shorter survival. Harrell’s C-index was 0.74. The median OS values for low-, low-intermediate-, high-intermediate-, and high-risk groups were 14, 7.7, 4.7, and 1.8 mo, respectively. Limitations include the retrospective design. ConclusionsWe developed a prognostic model and identified a subgroup of patients in whom third-line LPD treatment has no meaningful benefit. Our results need to be confirmed by prospective clinical trials. Patient summaryWe reported outcomes from third-line life-prolonging drugs in metastatic prostate cancer patients and developed a prognostic model that could be used to guide treatment decisions.