1: Early diagnosis of advanced prostate cancer may improve men's survival
Follow-up analysis from the ProtecT trial suggests that PSA testing of asymptomatic men can lead to early detection of advanced prostate cancer and may improve survival. This study examined outcomes for 492 men (ProtecT cohort), who after PSA testing, were diagnosed with metastatic, locally advanced (cT3-4) disease and/or had PSA ≥ 20ug/l and were excluded from randomisation in the ProtecT trial. Prostate cancer specific and overall survival was compared between this group of men and a cohort of men from the UK Anglia Cancer Network (ACN) (control cohort) who were matched in terms of age, year of diagnosis and disease severity.
Men within the ProtecT cohort had a reduced risk of death from prostate cancer (HR 0.29, 95% CI 0.38-0.53, p<0.0001) compared to ACN controls at 7.6 years. This difference was due to the lower risk of death among men who received non-radical treatment; there was no difference in the risk of death from prostate cancer among men who received radical treatment (radical prostatectomy or radiotherapy). Men in the ProtecT cohort had been invited to attend PSA testing and this suggests that wider PSA testing for asymptomatic men may be beneficial to diagnose advanced cancers at an earlier stage.
There are some key limitations of this study. Most importantly, this is an observational, non-randomized study. The control group was from a single region and was less fit overall then the ProtecT cohort. Although the authors tried to adjust for these differences, they acknowledge that lead-time and selection bias cannot be ruled out. Future controlled studies including the CAP trial (cluster randomised trial of PSA testing) which is expected to publish in 2017, will be critical to clarify the potential impact of wider PSA testing in the community.
2: Meta-analysis finds link between alcohol consumption and risk of developing prostate cancer
A new meta-analysis, published in the BMC, has concluded that there may be a small dose-response relationship between alcohol intake and prostate cancer risk. Researchers analysed data from 27 out of a possible 340 studies and found that the relative risk of prostate cancer was 1.08 (p<0.001), 1.07 (p<0.01), 1.14 (p<0.001) and 1.18 (p<0.001) for low, medium, high, and higher volume drinkers respectively, compared to non-drinkers. This was a significant dose-response rate (ptrend<0.01).
This study statistically corrected for misclassification or abstainer bias which can occur when former and occasional drinkers are counted as non-drinkers. It has been shown that this can lead to an underestimate of alcohol risk as former/occasional drinkers are often in poorer health than the general population and may include people who have stopped or reduced alcohol consumption as they age or face poor health. In fact, a sub-analysis that only included studies without abstainer bias, showed a stronger relative risk of 1.22 (p<0.05) for drinkers versus abstainers.
Taken together this study indicates that increased alcohol consumption may increase the risk of developing prostate cancer. The increase in risk however is small, and the limited number of studies included in the analysis may weaken the robustness and and reproducibility of the results. It will be important to see if future studies and meta-analysis also support this conclusion.