This news release reports on an attempt to measure the impact of the US Preventive Services Task Force (USPSTF) recommendations on PSA testing. A main point of emphasis in the release is the fact that diagnoses of intermediate- and high-risk prostate cancer were reduced after the draft guideline was changed due to the USPSTF “thumbs down” on the PSA test. While the release contends based on that finding that the USPSTF guidelines may lead to “missing important opportunities to spare men with higher risk cancers from progressive disease and cancer death,” the larger question of whether more or fewer men will get advanced prostate cancer and die from it isn’t addressed by the study — and the release should have been clearer about that fact, rather than headlining the release, “More men at risk of prostate cancer…” Perhaps just as important — but given less air time in the release — is the fact that there are fewer cases of low-risk cancers being diagnosed. This finding suggests that the USPSTF guideline seems to be effective in reducing overdiagnosis.
This study and the subsequent release raise questions about our societal perspective on the trade off between under- and over diagnosis of serious diseases like prostate cancer. Reducing overdiagnosis of low-risk disease has obvious health and economic benefits, but it’s possible that reduced screening might also lead to a small increase in the risk of dying from an aggressive cancer (although high-quality evidence to date doesn’t necessarily support this supposition as noted below in our review). Many people are unwilling to accept the flaws of screening tests–and the fact that the absolute benefits of screening programs are often quite small. This has been a contentious issue in the breast cancer screening world–where the evidence-based supporters for more rational screening are portrayed as heartless killers of women. As demonstrated by this study and news release, It’s also an ongoing concern in prostate cancer arena.
There is no mention about the costs of PSA tests or of the resulting low-risk cancers that may be unnecessarily irradiated, surgically extracted, or robotically removed. Similarly, there’s no mention of the costs of treating advanced cancer — both for health care (advanced cancer treatments can be extremely expensive–e.g., Provenge) and life years lost.
The apparent benefit of the USPSTF guidelines is the 37.9% reduction in the incidence of low-risk cancers–the over-diagnosed cancers that lead to over-treatment. While this benefit takes second billing to the potential risks of finding fewer higher-risk cancers in the release, there is at lease some discussion of this benefit. The fact that the rate of non-localized cancer did not increase in the study is reassuring–though the follow-up time is actually way too short to know whether trend will be durable.
The harm of not screening is implied to be an increased risk for prostate cancer mortality because diagnoses of high-risk cancers could be delayed. We’ll award a Satisfactory here, although we’d note that we don’t have high quality data supporting this supposition. The PIVOT trial of surgery vs. watchful waiting for men who were mostly screen-detected was negative. Only post-hoc analyses showed a potential survival benefit for aggressively treating high-risk cancers. One modeling study suggested that screening can be associated with net gain of quality-adjusted life years–though the 95% confidence interval also includes a net loss.
Another potential harm associated with screening are the adverse effects of treatment (whether necessary or unnecessary). The release notes that “radiation therapy and surgery have a negative impact on quality of life,” but this is somewhat euphemistic as we’re talking about potential for incontinence, impotence, and biopsy-related sepsis as well as death. There are hard numbers citing the rates of incontinence and impotence related to prostate surgery, so those certainly could have been cited here discussing harms.
The release contains a reasonable description of how the study was carried out. But there are a couple of major problems. One is that these data are observational in nature — we don’t actually know that less frequent screening is the causal factor leading to fewer prostate cancer diagnoses. Yet the assumption throughout the release is that the guidelines are the direct cause of the reduction in cancer diagnoses. Second, the release makes no real attempt to differentiate between prostate cancer diagnoses and prostate cancer mortality. The message from the release is that fewer diagnoses will likely lead to more aggressive cancers, but as noted above, the evidence supporting that scenario is not strong and this study actually didn’t find an increase in non-localized cancers.
We think there’s some fear-mongering going on related to the downside of following USPSTF guidance. Specifically the headline, which states that “more men are at risk of prostate cancer” due to following these guidelines. While it’s true that fewer men are being diagnosed with cancer, the idea that more men are “at risk” of aggressive cancer isn’t addressed by the study at all and may not be true. The study actually found that the rate of non-localized cancer did not increase during the study. The headline seems very one-sided considering that the study also shows a steep drop in the diagnosis of low-risk cancers, something which has clear and tangible benefits.
The release does not discuss funding for the study and does not disclose the fact that some authors have financial relationships with companies that make prostate cancer tests and treatments.
The alternatives are to screen (or at least screen more selectively) vs. not to screen. Although the story at least raises the comparison, the only way to truly compare the alternatives is to look at mortality outcomes, ideally with randomized trials. We have data from the ERSPC (European Randomised Study of Screening for Prostate Cancer) showing that screening reduces mortality by about 1/1000; the US PLCO (Prostate, Lung, Colorectal, and Ovarian) Cancer Screening Trials was negative. A key message is that men need to make informed decisions and be aware that a potential trade off with not screening is that the risk of dying from prostate cancer might be slightly increased. However, the current study is unable to provide data to quantitate that risk.
It is pretty clear from the release that PSA testing and related treatment are widely available.
The release establishes what is new and noteworthy about this study. There are no inappropriate claims to novelty.
The headline is arguably unjustified, but since we’ve already dinged the release for that infraction above, we’ll award a Satisfactory here since we see nothing else that’s egregious.