Reduced cancer screenings in Covid-19

Elective procedures and routine medical visits have declined since the Covid-19 pandemic. As we noted in a previous blog, this trend is not all bad, because there will likely be a decline in harmful unnecessary care.

A recent analysis from the EPIC Health Research network found a similar pattern for preventive cancer screenings. The analysis used electronic health record data from 2.7 million patients in the US and compared the rates of screening for cervical, breast, and colon cancer in the pre-Covid period with the current period. They found that screening appointments in March 2020 decreased by 86-94% compared to the average number of screening appointments that occurred monthly from January 1, 2017 through January 19, 2020.

What effect will this dramatic decline in screening have on patient health? The authors of the EPIC report think it could be dire. They go so far as to write that “Life years lost from delayed screening may be compared to life years gained from COVID precautions.”

Disease-specific vs all-cause mortality

Is this grim prediction likely? There are several points to consider. First, while cancer screening has been shown to reduce disease-specific mortality (the risk of dying of cancer), there is much less evidence of the benefit on all-cause mortality (the risk of dying overall). In 12 randomized trials of screening, reviewed by Dr. Vinay Prasad and colleagues in The BMJ, seven did not show a decline in overall mortality despite lower rates of disease-specific mortality. In some cases, overall mortality in the screening group was higher than in the non-screened group. How can this be?

One likely explanation is that the negative health outcomes from screening may counteract the benefits. While cancer screening reduces some cancer deaths, it leads to many more false positives, as well as cases of overdiagnosis and overtreatment. For example, screening 10,000 women age 50-59 for breast cancer every two years avoids 8 breast cancer deaths but leads to 932 false positives and 159 unnecessary biopsies. Unnecessary surgeries, chemotherapy, and complications from tests and procedures have a negative effect on health, which may reduce overall mortality in the screened group.

The authors of the EPIC report should have included not only the potential cancer deaths from lack of screening, but also the potential false positives and cascade events avoided, and the lack of evidence around the overall mortality benefits of screening.

Who is not getting screened?

Not everyone is equally likely to benefit from cancer screening. We don’t screen every person for every cancer, because the likelihood that young adults have cancer is very low, which makes it more likely they will be harmed by screening than helped. However, in very old age, cancer screening also becomes less beneficial because people are less likely to live long enough to experience any benefits from screening, and they are more susceptible to harmful complications of testing and treatment. For example, the US Preventive Services Task Force recommends screening for colon cancer only from age 50 to 75.

However, many people are screened for cancer even though they are unlikely to benefit. Nursing homes often screen very old people for cancer, even though are likely to be harmed by surgery or treatment if cancer was found. In one 2014 study, among older patients with very high mortality risk, 37.5% were screened for breast cancer, 30% were screened for cervical cancer, and 40% were screened for colorectal cancer. For women who had a hysterectomy for benign reasons, 34% to 56% still had cervical cancer screening within the past 3 years. Although cervical cancer screening is not recommended for young women age 15-20, an estimated 1.6 million pap tests are performed on women in this age group unnecessarily each year.

In the EPIC analysis, there is no information about the ages or risk levels of patients who have paused screening, only an overall percentage of fewer patients being screened. If most of the people who avoided screening in March 2020 were those at the lowest risk, then a reduction in screening may not be a bad thing overall– especially if the number of blatantly inappropriate screenings declined. However, with the information we have, we do not know which patients have avoided screening, making it impossible to estimate the real numbers of lives lost–or harm reduced–from this pause in screening.

An opportunity for research

The authors of the EPIC report make it clear what is at stake–lives lost due to reduced screening. However, it is very likely this number is overestimated, given the high rates of inappropriate screening in the real world, and the potential negative effects of screening on overall mortality.

While the true impact of the sudden halt in screening due to Covid-19 remains unknown, we have the opportunity to find out in the future. Such a drastic change in screening is unusual, so we should track the results of this historical experiment to better understand the actual health effects–both beneficial and harmful–of cancer screening.