Background
Evidence concerning third-line life-prolonging drugs (LPDs) in the treatment of metastatic castration-resistant prostate cancer (mCRPC) patients is incomplete.
Objective
To 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 participants
Patients 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 analysis
Association 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 limitations
Of 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.
Conclusions
We 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.
