Prognostic significance of plasma chromogranin A levels in hormone-refractory prostate cancer patients treated on Cancer and Leukemia Group B (CALGB) 9480.

4557 Background: The extent of neuroendocrine differentiation in prostate cancer correlates with aggressive disease and progression to hormone refractory prostate cancer (HRPC). Elevated plasma chromogranin A (CgA) levels in prostate cancer patients may reflect more extensive neuroendocrine phenotype. We therefore sought to test the hypothesis that CgA levels are of prognostic value in patients with HRPC. METHODS: Pretreatment plasma was collected from 390 patients with metastatic HRPC enrolled in CALGB 9480, a study of 3 different dose levels of suramin. Plasma CgA levels were determined in 321 of the samples in duplicate using a quantitative sandwich immunoassay (DAKO Corp. Carpinteria, CA, Cat. No. K0025). The proportional hazards model was used to assess the prognostic significance of CgA in predicting overall survival. RESULTS: Plasma CgA levels ranged from 7.7-19.3 U/L, with a median level of 12 U/L. In univariate analysis plasma CgA levels inversely correlated with survival times at the median CgA level, CgA ≤ 12 versus > 12 with survival 17 months (95% CI 14-19) compared to 11 months (95% CI 8-14, p = 0.014) and at all exploratory cut points including CgA ≤ 9.5 versus > 9.5 with survival 19 (95% CI= 16-20) months compared to 12 months (95% CI= 9-14, p = 0.002). In multivariate models adjusting for performance status, prostate specific antigen, lactate dehydrogenase (LDH), plasma CgA levels remained predictive of overall survival. The hazard ratio was 1.326 for patients whose CgA levels were above 9.5 compared to patients whose levels were < 9.5 (95% C.I. 1.045-1.68, p-value 0.020). CONCLUSION: These results support the hypothesis that plasma CgA levels can predict outcome in HRPC patients. No significant financial relationships to disclose.

Duke Scholars

Author Susan Halabi Biostatistics & Bioinformatics, Division of Biostatistics