Welcome to Journal Club! For discussion today is the following:
Article: Increasing incidence of metastatic prostate cancer in the United States (2004–2013)
Authors: A B Weiner, R S Matulewicz, S E Eggener and E M Schaeffer
Journal: Prostate Cancer and Prostatic Diseases. July 19, 2016
Background
Prostate cancer cells secrete an enzyme called Prostate Specific Antigen (PSA) into the bloodstream. Measuring the PSA level has been a way of screening for prostate cancer. In 2008 and again in 2012, the US Preventive Services Task Force (USPSTF) came out with recommendations to curtail the use of PSA for screening. The argument was that it led to the diagnosis of a lot of low risk prostate cancers that left alone would not grow to endanger life. Also, the test led to procedures that patients did not really need but which could lead to complications eg. impotence. Since 2012, there has been decrease in the use of PSA for screening,
The question among urologists has always been whether this recommendation would lead to ta spike in prostate cancer cases.
A group from Northwestern in Chicago, led by a Dr Edward Schaeffer decided to find out.
Study type
The study was retrospective.
Using the National Cancer Data Base (NCDB), they found all men who had been diagnosed with prostate cancer from 2004 to 2013. From 1089 institutions that reported each year in that time period, they got 767 550 patients.
The patients were split into risk groups (depending on the extent of the cancer when diagnosed). The groups were low, intermediate, high and metastatic. The incidence of prostate cancer for each risk group was then compared yearly to the incidence in 2004.
Of the 767 550 men, 32% had low, 45% intermediate , 20% high risk and 3% had metastatic disease. They teased out information from the data with appropriate statistical tools.
Results
Of all the groups, the one that saw the most significant increase, relative to 2004 was the metastatic one. In 2004, there were 1685 cases. In 2013, 2890. – a 72% increase. The largest increase was seen in men aged 55 to 69 years. In this group, the increase was actually 92%.
Comparably, the incidence of low-risk prostate cancer actually fell.
Discussion
One can probably argue that the decrease in using PSA for screening may be causing the inability to catch the very aggressive types of prostate cancer. The problem though is that, the increase was seen even before the 2008 recommendation of the USPSTF came out.
Another factor could be an increase in the aggressiveness of prostate cancer. Also the use of MRI imaging has improved diagnosis and that can increase the numbers. Lastly, the population may just be getting older and sicker.
Perhaps the biggest flaw of the study was that the authors didn’t calculate a national annual incidence rate – the number of metastatic cases as a percentage of the US population. They looked at it as a percentage of cases from about a 1000 hospitals. They argue in the paper that with over 700 000 patients,they thought their results reflected national patterns.
Conclusion
Even though this study has it’s flaws, the fact remains that yearly PSAs can help screen for prostate cancer. In patients at high risk – those with a strong family history and blacks – it may be highly recommended. Done yearly, it provides a trend that can be very informative.
The recommendation is to start screening at age 45 in those at high risk and 50 for those at low risk.
For my lay male friends reading this who are black and 45 or older or not black but with a family history, if you haven’t started screening already, please see your primary care physician as soon as possible. By the way, just in case you ask, NO, you cannot do the exam yourself. It is very much unlike a breast self exam that women do!