This story about a new analysis of data on PSA screening includes many important details about the meaning of the study results. It points out harms of prostate cancer treatment and concerns about overdiagnosis and overtreatment.
However, the cautionary statements are pushed down to the bottom half of the story. The headline and lead paragraphs include statements about screening saving lives, without telling readers about absolute risks or about limitations and uncertainties in the new analysis. By reporting a relative risk reduction of up to 32 percent–without also reporting that since fewer than 3 out of 100 men die of prostate cancer the absolute risk reduction is likely less than 1 percent–the story leaves readers with an inflated sense of how many lives might be saved by increased screening.
Basically, this study adds very little to our current understanding of the benefits of prostate cancer screening–not much has changed (see our STAT News review to better understand why). Yet readers of this LA Times story are likely to come away with a different take.
The story does not address the cost of the PSA test itself or of follow-up testing or treatment.
The story reports only the study’s estimate of a relative risk reduction of 25 to 32 percent. This figure is meaningless without reporting the underlying absolute risk of dying from prostate cancer. The American Cancer Society states that “About 1 man in 39 will die of prostate cancer.” To put it another way, of every 100 men in the US, fewer than 3 will die of prostate cancer and more than 97 will die of something else. The study’s estimate of relative risk reduction might translate into fewer than 2 men dying of prostate cancer and more than 98 dying of something else. However, since many men are already screened with PSA tests, the actual reduction in deaths is likely to be smaller than that. For a more accurate way to capture the measured benefits, see STAT’s story.
The story warns of overdiagnosis and overtreatment, and then specifically notes harms to “sexual function, urination and bowel movements.” The story also quotes an expert who notes that “the way screening has been implemented in the United States leaves much to be desired” and that the debate should be about “whether we can change our behavior so that it does more good than harm.”
However, while the headline and lead paragraphs focus on the claim that PSA screening saves lives, the first mention of overdiagnosis and overtreatment does not appear until more than halfway into the story.
The story does report at the top that this study is “a new analysis of existing clinical trial evidence.” It cites two big studies, PLCO and ERSPC, and recommendations based on them that were issued by the US Preventive Services Task Force.
However, readers are not told specifically that this new analysis is based on data from those two specific studies, nor does it explain that the authors used a variety of methods to estimate the differences in death rates from prostate cancer based on screening practices used in these underlying studies, which involved a number of assumptions and simplifications. The story portrays the results of the analysis as far more clear-cut and definite than even the authors claim. See our STAT review for an example of a story that more accurately discussed the evidence.
The story reports that a PSA test result is just the start of a decision-making process, and that many men reasonably choose to have little or no follow-up testing or treatment after a positive PSA result.
As with the STAT News story, this one didn’t note the financial disclosures of the study authors, including the senior author, Ruth Etzioni, who disclosed she owns equity in a company developing medical imaging technology that it says could be applied in prostate cancer patients. Dr. Etzioni stated that she does not consider the equity ownership to be a conflict of interest, but considering that an increase in PSA screening would boost demand for more precise and less invasive follow-up testing, it appears that her company would benefit.
While the story does quote an independent source, it would have been helpful to note that he consults for the medical industry.
The study was funded by the National Cancer Institute. While that source does not raise any red flags, and the study stated that the funder had no role in the study, news stories are more informative when they note study funding.
The story is all about the comparison of screening to not screening.
It is clear that PSA screening is widely available.
The story does not explain how or why this analysis of two trials is potentially more informative than the original separate studies themselves.
There are original quotes in the story.