Prognostic correlation of cell cycle progression score and Ki-67 as a predictor of aggressiveness, biochemical failure, and mortality in men with high-risk prostate cancer treated with external beam radiation therapy.

Objectives: Ki-67 is a proliferation marker in prostate cancer. A prognostic RNA signature was developed to characterize prostate cancer aggressiveness. The aim was to evaluate prognostic correlation of CCP and Ki-67 with biochemical failure (BF), and survival in high-risk prostate cancer patients (pts) treated with radiation therapy (RT).

Methods: CCP score and Ki-67 were derived retrospectively from pre-treatment paraffin-embedded prostate cancer tissue of 33 men diagnosed from 2002 to 2006. CCP score was calculated as an average expression of 31 CCP genes. Ki-67 was determined by IHC. Single pathologist evaluated all tissues. Factors associated to failure and survival were analyzed.

Results: Median CCP score was 0.9 (-0-1 - 2.6). CCP 0: 1 pt; CCP 1: 19 pts; CCP 2: 13 pts. Median Ki-67 was 8.9. Ki-67 cutpoint was 15.08%. BF and DSM were observed in 21% and 9%. Ki-67 ≥ 15% predicted BF ( = 0.043). With a median follow-up of 8.4 years, 10-year BF, OS, DM and DSM for CCP 1 vs. CCP 2 was 76-71% ( = 0.83), 83-73% ( = 0.86), 89-85% ( = 0.84), and 94-78% ( = 0.66). On univariate, high Ki-67 was correlated with BF ( = 0.013), OS ( = 0.023), DM ( = 0.007), and DSM ( = 0.01). On Cox MVA, high Ki-67 had a BF trend ( = 0.063). High CCP score was not correlated with DSM.

Conclusions: High Ki-67 significantly predicted outcome and provided prognostic information. CCP score may improve accuracy stratification. We did not provide prognostic correlation of CCP and DSM. It should be validated in a larger cohort of pts.