Metastatic burden in newly diagnosed hormone-naive metastatic prostate cancer: Comparing definitions of CHAARTED and LATITUDE trial.

Objectives: No uniformity exists in the definition of metastatic burden in metastatic hormone-naive prostate cancer (mHNPC) across clinical trials making their comparison challenging. We explored definition agreement and prognostic significance of bulky mHNPC according to the CHAARTED and LATITUDE trial.

Materials And Methods: Since 2014, 95 patients with newly diagnosed mHNPC were prospectively registered. For this study, they were categorized as having high-volume (HVD) vs. low-volume (LVD) and high-risk (HRD) vs. low-risk disease (LRD) according to the definition of CHAARTED and LATITUDE, respectively. Agreement was tested using Cohen's κ coefficient. The Kaplan-Meier method was used to compare castration-resistant prostate cancer-free survival (CRPC-FS) and overall survival (OS). Prognostic significance was analyzed using Cox regression models.

Results: In total, 44 (46%) and 46 (48%) patients showed HVD and HRD, respectively. Cohen's κ coefficient was 0.83 indicating "almost perfect" agreement (P<0.001). Median CRPC-FS was 40 (95% CI: 25-55) vs. 11 months (95% CI: 8-14) for LVD and HVD (P = 0.001); 40 (95% CI: 27-53) vs. 11 months (95% CI: 8-14) for LRD and HRD (P<0.001), respectively. Median OS was not reached vs. 51 months (95% CI: 0-102) for LVD and HVD (P = 0.001); not reached vs. 51 months (95% CI: 2-100) for LRD and HRD (P = 0.003), respectively. The prognostic significance of both definitions remained significant in the multivariate model for CRPC-FS (P = 0.012 and P = 0.003).

Conclusions: There is an excellent agreement between the definitions of bulky mHNPC in the CHAARTED and LATITUDE trial. Both definitions have significant prognostic value for predicting worse CRPC-FS and OS.