A problem with cancer screening (at least in the USA)


According to a recent report in the American Journal of Preventive Medicine, only 5.6 percent of a sample of 3,677 Americans of 18 years of age or older could correctly evaluate four simple statements about cancer screening.

The abstract of the original study by Roberts et al. is available on line and so is a commentary on the Reuters web site.

While this study was not specific to prostate cancer screening, it does seem to clearly demonstrate that the vast majority of Americans do not really appreciate the full spectrum of the risks and benefits of screening for cancer.

Here is a list of the four statements about screening tests given to participants in the study, and how they responded to the statements (by answering either “True” or “False” to each statement):

  • Statement 1: “These tests can definitely tell that a person has cancer.”
    • The correct response to this statement is “False”.
    • Just over 70 percent of participants gave the correct response.
  • Statement 2: “When a test finds something abnormal, more tests are needed to know if it is cancer.”
    • The correct response to this statement is “True”.
    • Almost 92 percent of participants gave the correct response.
  • Statement 3: “When a test finds something abnormal, it is very likely to be cancer.”
    • The correct response to this statement is “False”.
    • Just over 33 percent of participants gave the correct response.
  • Statement 4: “The harms of these tests and exams sometimes outweigh the benefits.”
    • The correct response to this statement is “True”.
    • Only about 20 percent of participants gave the correct response.

Numerically, just 189/3,677 participants in the survey gave the correct responses to all four statements (i.e., their responses were 100 percent accurate). However, all four of these statements are highly relevant to a man’s understanding of the appropriateness of screening for risk of prostate cancer.

The study also showed that four different factors reduced the likelihood that participants would respond correctly to all four statements:

  • Being male
  • Being a member of a racial/ethnic minority
  • Having a lower standard of education
  • Having a higher level of “cancer fatalism”

The “good news”, on the other hand, was that participants who had worked with their physician to make decisions about colon cancer screening (shared decision making) were

  • More likely to respond accurately that more tests are needed after a screening test result is positive
  • More likely to know that an abnormal screening test result was nonetheless “not very likely to be cancer”

However, the combination of factors (a screening test that is not of high specificity and a screening test exclusively for males) would seem to be a recipe for poor appreciation of the risk/benefit equation when it comes to how an individual man in America is likely to think about prostate cancer screening and what the results of a PSA test actually mean.

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