March 15, 2012

Headlines don’t help on prostate cancer screening study: “reduces death” vs. “isn’t saving lives”

Posted By

Comments

Please note, comments are no longer published through this website. All previously made comments are still archived and available for viewing through select posts.

Gregory D. Pawelski

March 15, 2012 at 10:11 am

Thanks Gary! My head hurts enough trying to read these headlines, let alone the text.

Tim Bartik

March 15, 2012 at 4:11 pm

Gary:

I believe the journalistic coverage is somewhat confused because the researchers did not clarify what their study potentially CAN show and can’t show.

If you look at their study through the lens of statistics, it is clear that the European study, and all other prostate cancer screening studies, are vastly underpowered to detect effects on all-cause mortality. In brief, we have all cause mortality at around 20% in the control group, and prostate cancer mortality at around 0.5%. We are trying to detect a reduction in mortality of 0.1%. The European study has a large enough sample to detect a statistically significant decline in prostate cancer mortality from 0.5% to 0.4%. But it has nowhere near large enough a sample to have any hope of detecting a statistically significant change from 20% to 19.9%. It is hard to detect such a small RELATIVE change unless you have a huge sample, by my calculations a sample of over 5 million. For more details, see my comments to a post today at the blog prostate cancer infolink on the European study..

In any event, I think the journalism is confused because few journalists have sufficient statistics background to readily do a power analysis of empirical studies. The researchers did not help journalists by explaining this issue.

Tim Bartik

March 15, 2012 at 4:14 pm

Correction: I meant to say over 4 million is the required sample size, not over 5 million.

Tom Emerick

March 20, 2012 at 6:05 am

An excellent and timely write up. My vote is that PSA tests do not save lives. Your comments about small relative changes are spot on.

I told my doctor a few year ago to do no more PSA tests on me.

COMMENTS button We welcome comments, which users can leave at the end of any of our systematic story reviews or at the end of any of our blog posts.

But before leaving a comment, please review these notes about our policy.

You are responsible for any comments you leave on this site.

This site is primarily a forum for discussion about the quality (or lack thereof) in journalism or other media messages (advertising, marketing, public relations, medical journals, etc.) It is not intended to be a forum for definitive discussions about medicine or science.

We will delete comments that include personal attacks, unfounded allegations, unverified claims, product pitches, profanity or any from anyone who does not list a full name and a functioning email address. We will also end any thread of repetitive comments. We don”t give medical advice so we won”t respond to questions asking for it.

We don”t have sufficient staffing to contact each commenter who left such a message. If you have a question about why your comment was edited or removed, you can email us at feedback@healthnewsreview.org.

There has been a recent burst of attention to troubles with many comments left on science and science news/communication websites. Read “Online science comments: trolls, trash and treasure.”

The authors of the Retraction Watch comments policy urge commenters:

“Shed light, not just heat. Facts, challenges, disagreements, corrections — those are all fine. Attacking the person, instead of the idea or the interpretation, is neither acceptable nor helpful.”

We”re also concerned about anonymous comments. We ask that all commenters leave their full name and provide an actual email address in case we feel we need to contact them. We may delete any comment left by someone who does not leave their name and a legitimate email address.

And, as noted, product pitches of any sort – pushing treatments, tests, products, procedures, physicians, medical centers, books, websites – are likely to be deleted. We don”t accept advertising on this site and are not going to give it away free.

The ability to leave comments expires after a certain period of time. So you may find that you’re unable to leave a comment on an article that is more than a few months old.