False-Positive CT Findings Do Not Increase Worry in Lung Cancer Patients

The US Preventive Services Task Force (Rockville, MD, USA) recently recommended computed tomography (CT) lung screening for individuals at high risk for cancer, but a potential problem with CT scanning is that many patients will have positive findings on the screening test, only to be considered cancer-free with additional scanning. Many policymakers have expressed concern that this high false-positive rate will cause patients to become needlessly anxious.

A new study of US National Lung Screening Trial (NLST) participant responses to false-positive diagnoses, however, found that those who received false-positive screening findings did not report heightened worry or lower quality of life in comparison with participants who received negative screen findings. “Most people anticipated that participants who were told that they had a positive screen result would experience increased anxiety and reduced quality of life. However, we did not find this to be the case,” said Dr. Ilana Gareen, assistant professor (research) of epidemiology in the Brown University (Providence, RI, USA) School of Public Health and lead author of the study published online July 25, 2014, in the journal Cancer.

The NLST’s major finding, announced in 2010, was that screening with helical CT scans reduced lung cancer deaths by 20% compared to screening with chest X-rays. The huge trial spanned more than a decade, enrolling more than 53,000 smokers at 33 sites. In the new study, the investigators followed up with a subset of participants at 16 sites to assess the psychological effects of the CT and X-ray screenings compared in the trial.

“In the context of our study, with the consent process that we used, we found no increased anxiety or decreased quality of life at one or six months after screening for participants having a false-positive,” Dr. Gareen said. “What we expected was that there would be increased anxiety and decreased quality of life at one month and that these symptoms would subside by six months, which is why we measured at both time points, but we didn’t find any changes at either time point.”

The unexpected similarity between the participants with a negative and a false-positive screen findings is not because getting a false-positive diagnosis is at all pleasant, according to Dr. Gareen, but presumably because study participants understood that there was a high likelihood of a false-positive screen findings. “We think that the staff at each of the NLST sites did a very good job of providing informed consent to our participants,” she said. “In advance of any screening, participants were advised that 20%–50% of those screened would receive false positive results, and that the participants might require additional work-up to confirm that they were cancer free.”

To make its evaluations, Dr. Gareen’s team surveyed 2,812 NLST participants for the study. Patients responded well, with 2,317 returning the survey at one month after screening and 1,990 returning the survey at six months. The survey included two standardized questionnaires: the 36-question Short Form SF-36, which elicits self-reports of general physical and mental health quality, and the 20-question Spielberger State Trait Anxiety Inventory.

Dr. Maryann Duggan and her staff from the outcomes and economics evaluation unit at Brown administered the questionnaires by mail with telephone follow-up as required. In the study analysis, the researchers allocated people into groups based on their ultimate accurate diagnoses: 1,024 participants were “false-positive,” 63 were “true positive,” 1,381 were “true negative,” and 344 had a “significant incidental finding,” meaning they didn't have cancer but instead had another possible problem of medical importance.

The findings were clear after statistical adjustment for factors that could have had a confusing influence. Whether participants received X-rays or the helical CT scans, the questionnaire scores of those with false-positive diagnoses remained similar to those who were given true negative diagnoses. Meanwhile, the scores of the true positive participants who were diagnosed with lung cancer markedly worsened over time as their battle with the disease took a physical and psychological toll.

Because the individuals received the questionnaires at one and six months, it is possible that study participants receiving a false-positive screen result suffered anxiety and reduced quality of life for a short time after receiving their screen result, according to Dr. Gareen. However, by one month after their screening, there was no evidence of a difference between the screen result groups.

Dr. Gareen noted that the findings should inspire physicians to recommend appropriate screenings, in spite their high-false positive rates, as long as patients are accurately informed of the probability of a positive screen result and its implications. The data provide evidence that the NLST consent process provided a good model for recommending those undergoing screening, she reported.

Related Links:
Brown University
US Preventive Services Task Force