Weekly, seasonal variations in PSA should not affect biopsy decision
MedWire News: Men's prostate-specific antigen (PSA) levels vary according to season and weekday, say UK researchers, who add that the variation is small and should not affect the decision to take a prostate biopsy.
"PSA remains the best available biomarker for the early detection of prostate cancer," say David Connolly from Belfast City Hospital, Northern Ireland, and colleagues.
However, PSA is inherently variable, they add, with many factors unrelated to prostate cancer known to cause transient elevations.
Previous studies have indicated season as one such factor, with PSA levels higher in the summer. Thus, Connolly et al evaluated whether this PSA seasonality existed in a large (n=53,224) population of unscreened men, whose PSA levels were compared with meteorological data on a daily, weekly, monthly, and seasonal basis.
All men were aged 45-74 years and had an initial PSA of less than 10 ng/ml, which was measured on a weekday between 2002 and 2006. Weather data for this period was obtained from the UK Met Office, where daily information was only available for 2006.
The number of men with a PSA level of at least 3 ng/ml - indicating the need for biopsy - was calculated for each month, and the researchers noted it was significantly larger among older men.
Overall, median PSA levels were significantly higher in spring compared with other seasons, at 1.18 versus 1.10 ng/ml.
However, participants' mean age was also marginally higher during spring than during other seasons, at 59.7 versus 59.4 years, and after the researchers adjusted for this finding, the association between PSA level and season no longer remained.
With regard to individual meteorological factors, PSA was not associated with daily, weekly, or monthly hours of sunshine, rainfall, or mean temperature. However, age-adjusted PSA levels did vary by weekday, with higher levels on Thursday and Friday versus Monday, Tuesday, and Wednesday, at medians of 1.16 versus 1.10 ng/ml.
This weekday variation "suggests that there may be social reasons involved as opposed to a true biological basis," write Connolly et al in the journal Prostate Cancer and Prostatic Diseases.
"One possible factor is sexual behavior and ejaculation," they add.
Connolly and team conclude that contrary to the recommendations of previous researchers, "the decision to proceed to prostate biopsy should be independent of season or climatic conditions."
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By Sarah Guy