Improving the efficacy of targeted trials by multiple-marker analysis in castration-resistant prostate cancer

Abstract

Objectives: In order to improve the efficacy of targeted therapy trials, the expression profiles of several molecular markers that are potential candidates for targeted therapy were analyzed in patients with progressive castration-resistant prostate cancer.

Methods and materials: Paraffin-embedded samples of tumor tissue from 51 patients obtained from biopsies of metastases or remaining prostates were analyzed immunohistochemically for the expression of EGFR, PDGFRβ, Her-2/neu, c-Kit, and VEGF. Staining was analyzed according to the percentage of positively stained tumor cells and the intensity of staining.

Results: According to the different cut-off values of 10%, 30%, 50%, or 70% for the percentage of positively stained cells, different rates of expression were found. Expression rates ranged from 30.6% to 61.2% for EGFR, from 34.7% to 57.1% for PDGFRβ, from 9.6% to 28.8% for Her-2/neu, from 12.5% to 22.4% for c-Kit, and from 51.1% to 74.5% for VEGF. Defining positive expression as ≥ 30% positively stained tumor cells, with an intensity of staining of ≥ 2+, resulted in positive expression of EGFR in 38.8%, PDGFRβ in 24.5%, Her-2/neu in 13.5%, c-Kit in 6.4%, and VEGF in 44.7% of the patients.

Conclusions: Our results demonstrate simultaneous expression of several markers in castration-resistant prostate cancer tissue. Translation of the results into modern, multi-arm clinical trial designs will improve the efficacy of recruiting and obtaining results, compared with multiple double-arm trials.