When Informed of Overdetection, Do Patients Still Want Screening?

March 13, 2015

The issue of overdetection of cancer from screening must be addressed sooner than later, say experts.

Women invited to participate in breast cancer screening should be informed about issues related to possible overdetection of cancer, according to a study published in The BMJ.

Researchers from the U.K. performed an online survey with 1,000 men and women to determine the level of overdetection people would find acceptable in screening for breast, prostate, and bowel cancer. They also assessed if acceptability is influenced by the magnitude of the benefit from screening and the cancer specific harms from overdetection.

The mean age of the respondents was 46.9; 51% of respondents were women. The survey included questions on screening for breast cancer (for women), prostate cancer (for men), and bowel cancer (for both men and women). The researchers used the word “overdetection” rather than “overdiagnosis” throughout the survey.

They presented epidemiological information and described the treatment and its consequences. The respondents were then given two scenarios of benefit: one indicating a 10% reduction in cancer specific mortality and the second indicating a 50% reduction.

The results showed that there was a large variability between what respondents believed was an acceptable level of overdetection.

"We found that people have highly variable views about how much overdetection they would accept in cancer screening, with up to seven percent indicating they would accept no overdetection at all and up to 14 percent who would accept overdetection in the entire population,” lead author Dr. Ann Van den Bruel, director of the NIHR Oxford Diagnostic Evidence Cooperative and senior clinical research fellow in Oxford University's Nuffield Department of Primary Care Health Sciences, said in a release. “Across the different cancer types, people would accept a median of 113 to 150 people to be overdetected to avoid one person dying of cancer as a result of screening." There were also differences in acceptability according to cancer type. Acceptability in screening for bowel cancer was significantly lower than for breast and prostate cancer. Older respondents (over age 50) accepted significantly less overdetection, whereas people with higher education levels accepted more.

The researchers concluded that acceptability of overdetection in cancer screening was variable and that cancer screening invitations should include clear information on the likelihood and consequences of overdetection to allow people to make an informed choice.

A Response About Breast Screening
In an accompanying article, Alexandra Barratt, professor of public health at the University of Sydney, wrote that clinicians must come to an agreement regarding overdiagnosis in breast cancer screening so women can be better informed about their choices.

Breast cancer screening has been subject to considerable research over the past few decades, allowing more women than ever to be diagnosed in earlier stages of breast cancer. However, the increasing debate of overdiagnosis and subsequent overtreatment of the cancer is growing.

Barratt argued that introduction of new breast imaging technologies, such as tomosynthesis (3D mammography) or extending screening to older and younger women, should be delayed until incremental net benefit to women has been demonstrated in high quality studies.

"Breast cancer research has led the way in developing awareness of the potential harms of overdiagnosis and overtreatment among asymptomatic people who participate in cancer screening programmes," concluded Barratt. "Increasing awareness and understanding of overdiagnosis in relation to the early detection of lung and thyroid cancers, as well as breast and prostate cancers, is needed and should be prioritised in public communication initiatives."