Prostate specific antigen mass ratio potential as a prostate cancer screening tool

Abstract

Purpose: Studies suggest lowering the threshold of the prostate specific antigen test in obese men due to the hemodilution effect but prostate specific antigen may be affected by prostate volume and insulin resistance, which also increase with obesity. Thus, we examined the combined effect of these factors on prostate specific antigen.

Materials and methods: We analyzed 3,461 Korean men 30 to 80 years old with prostate volume data available who underwent routine evaluation. We examined the effect of plasma volume, homeostatic model assessment index, prostate volume and body mass index on prostate specific antigen, and prostate specific antigen mass and mass ratio (total circulating prostate specific antigen protein per prostate volume) by the trend test and/or ANOVA after adjusting for age and/or prostate volume.

Results: Body mass index had positive associations with plasma volume, the homeostatic model assessment index and prostate volume (p for trend <0.01). Prostate specific antigen had a positive association with prostate volume and a negative association with plasma volume (p for trend <0.01) but not with homeostatic model assessment index. The adjusted R(2) of prostate volume vs prostate specific antigen was greater than for plasma volume vs prostate specific antigen while for body mass index vs prostate volume it was less than for body mass index vs plasma volume (0.0892, 0.0235, 0.1346 and 0.3360, respectively). Prostate specific antigen mass was not associated with plasma volume or body mass index but it was still associated with prostate volume after adjusting for plasma volume or body mass index (p for trend <0.01). Mean prostate specific antigen mass ratio did not change significantly across body mass index, plasma volume or prostate volume quartiles in men older than 55 years.

Conclusions: It is not logical to lower the prostate specific antigen threshold based on only the hemodilution effect since body mass index related prostate volume enlargement can increase prostate specific antigen in obese men. Another tool is needed and prostate specific antigen mass ratio may be an option.