Introduction:

The incidence of prostate cancer (PCa) in Asia is lower than in Western countries but has been increasing rapidly in the last decade. Studies have previously suggested that Asian men present more frequently with advanced stage and high-grade PCa than Caucasian men. The unfavorable risk profile in Asian men could be partly explained by differences in screening and early detection practices. Differences at the genomic level also exist such as TMPRSS2-ERG fusions (prevalence of 50% in Caucasian vs. ~20% in Asian). Risk calculators such as the ERSPC calculator have been recalibrated for Chinese populations, outlining possible risk differences compared to Caucasians. We investigated the impact of race (Asian or Caucasian) on biopsy Gleason Score (GS) distribution in men diagnosed with PCa in tertiary referral centers in Toronto and Shanghai.

Methods:

We performed a retrospective study of 2175 men diagnosed with PCa at 2 tertiary referral centres, University Health Network, Toronto, Canada and Renji Hospital, Shanghai, China, between 2014 and 2017. The biopsy protocol between the two centres were similar (number of biopsy cores = 10-14). We compared the distribution of GS on biopsy between men in China and Canada. To take into account potential differences in biopsy grading between institutions, a pathologist in Toronto re-reviewed a random sample of 99 biopsies from Shanghai, blinded to institution, clinical information and GS. To study the association between race and GS at diagnosis, univariate and multivariable logistic regression analyses were performed adjusting for age, PSA and prostate volume.

Results:

The study population comprised 1032 vs. 1143 men diagnosed with PCa in Shanghai and Toronto, respectively. Median age at diagnosis (69 vs 65 years) and PSA (19.08 vs 6.24 ng/ml) was higher in Asian men compared to Caucasian men (p<0.001) whereas their prostates were smaller (34.2 cc vs 38.0 cc, p<0.001). In the 99 biopsies re-reviewed, the kappa coefficient between Shanghai and Toronto was 0.72. On univariate analysis, more GS8-10 (28.1%% vs 8.5%, p<0.001) were found in Asian than Caucasian men. On multivariable analysis, adjusting for age, PSA and prostate volume, GS8-10 in Asian men was significantly higher than in Caucasian men (OR 2.93, 95% CI 2.206-3.902, p=0.001). In the subset of men with PSA<10 ng/ml, GS8-10 in Asian men was significantly higher than in Caucasian men (OR 2.712, 95%CI 2.055-3.579, p=0.001). Limitations include the retrospective nature of this study and that tertiary referral centers might not be representative of the entire population.

Conclusion:

Our study confirms racial differences in PCa aggressiveness between Asian and Caucasian men. It is unclear why Asian men are diagnosed with higher GS on biopsy than Caucasian men but suggests that differences in screening might not be the sole explanation.

Funding: N/A