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The prospect of developing cancer is a frightening one. Sadly, this fear is leading many to undergo dangerous and harmful cancer screenings that, ironically, can cause the very diseases patients hope to avoid.
Any procedure or action needs to be evaluated not just on its benefits, but also on its costs. If a test saves one life but costs two, it’s not a benefit. It is not the benefit but the ratio of benefit to cost that judges a test. It is the unbalanced exposure to the benefits of cancer screening that have placed the public in an uninformed and, therefore, overly trusting and optimistic position.
There are a number of ways cancer screening can have a greater ratio of costs to benefits even if the benefits are accurately reported. A screening method may sometimes detect an early cancer. But the huge majority of people who are screened are healthy and don’t have that cancer but are exposed to the hazards of the screening, and false positives and overdiagnosis can cause healthy people to undergo unhealthy treatments. So, while the benefit may be a saved life, the cost may be more people dying from the test or the treatment. The cancers aren’t real, but the dangerous treatments are. The false cancer causes no danger, but the real chemo and radiation do. And, actually, the false cancer causes danger too because of the very real stress caused by the belief that you are living with cancer.
A systematic review of meta-analyses of cancer screening found that only three of ten studies found that cancer screening reduces the risk of dying from the cancer it was screening for. Even worse, not one found that cancer screening reduces your actual risk of death (1).
The most recent reminder of the costs of cancer screening is the little discussed thyroid cancer. Careful scientific research has revealed the best approach for most thyroid cancers: don’t get screened; don’t get treatment.
The popularization of ultrasound screening, CT scanning and MRI’s has led to a dramatic increase in the diagnosis of thyroid cancer, especially among women. But a new report by the International Agency for Research on Cancer (IARC) has uncovered the shocking real reason for the increase in thyroid cancer diagnoses. The IARC is the specialized cancer agency for the World Health Organization (WHO). And their landmark report reveals that the increase in diagnosis of thyroid cancer is due, not to improved diagnosis, but to overdiagnosis.
The report looked at thyroid cancer diagnosis in twelve highly developed countries. The researchers found a 50% rate of overdiagnosis for women in Japan, Scandinavia, England and Scotland and a 70-80% rate of overdiagnosis in the U.S., France, Italy and Australia. In men, thyroid cancer is being overdosed in 70% of French, Italian and Korean men, 45% of Australian and American men and in less than 25% of men in the other seven countries.
Altogether, the report found that, in the past two decades, 470,000 women and 90,000 men have been overdiagnosed with thyroid cancer. What the screening techniques are discovering are fairly harmless non-lethal diseases that are common and very unlikely to cause death or even any symptoms.
The cancer in these over half a million people was never real, but the harmful thyroidectomies, lymph node dissections and radiation they received were very real. That is, the screening for thyroid cancer has told people who never had cancer that they did and then subjected them to dangerous treatments that had no benefit (2).
This is the second important study that has implicated thyroid cancer diagnosis. An earlier study by an international panel of experts put together by the National Cancer Institute and published in JAMA Oncology found that a commonly diagnosed type of thyroid cancer is not actually a cancer at all.
Encapsulated Follicular Variant of Papillary Thyroid Cancer is a common form of thyroid cancer that often leads to removal of the thyroid and radiation treatment. Encapsulated Follicular Variant of Papillary Thyroid Cancer affects about 10,000 of the roughly 65,000 people diagnosed with thyroid cancer each year in the United States and about 45,000 people world wide.
But a recent study has concluded that this common form of thyroid cancer is not, it turns out, a cancer at all. That means that tens of thousands of people a year received radiation therapy that was never necessary and that is now realized to have only been harmful (3). As in the current study, these people received harmful and totally unnecessary treatments like radiation therapy.
Based on the new data, the IARC report “cautions against systematic screening of the thyroid gland and workup of small nodules, while careful monitoring may be a preferable option for patients affected by low-risk tumours.”
Unfortunately, the problem with thyroid cancer screening is not an anomaly.
The purpose of having a mammogram is to detect and treat breast cancer, the most common cancer in women, early. However, research by The Nordic Cochrane Centre has produced the alarming conclusion that getting mammograms “does not reduce the overall risk of dying, or the overall risk of dying from cancer (including breast cancer).”
The Cochrane review of seven studies that included 600,000 women found that the studies on screening by mammography that are adequately randomized show there is no statistically significant reduction in breast cancer mortality with screening (4).
Regular mammograms reduce the rate of death from breast cancer by only 0.1% according to a review of research (5). And, more thorough systematic reviews, including a Cochrane review, found that the power of mammograms to prevent death from breast cancer was actually only half that, or 0.05% (6,7). According to another systematic review of the research, one of the reasons screening does not prevent death by breasts cancer is because it does not improve the rate of advanced breast cancers (8).
But while there is no benefit, screening did significantly increase the number of lumpectomies and mastectomies as well as the number of women who underwent harmful radiation. These unnecessary treatments were, in part, because of screening’s early detection of cell changes that never would have grown into actual cancer. Detecting them, however, leads to treatment: unnecessary and potentially harmful treatment.
As in thyroid cancer, overdiagnosis is a problem in breast cancer screening. A systematic review found that when screening programs are offered, overdiagnosis levitates at 52% (9). Compared to a control group of women who were not screened, overdiagnosis of Danish women who were screened was 33% (10). According to a recent study published in the Journal of the American Medical Association, ten years or more of regular mammograms leads to a false positive in over 60% of women (11).
Balancing the benefits of mammography with the costs of overdiagnosis and unnecessary treatment, the Cochrane review concluded that for every 2,000 women screened for breast cancer by mammography, one will prevent death by breast cancer while ten healthy women will receive unnecessary treatment, including partial or whole breast removal, radiation or chemotherapy. So mammograms may do harm without having benefit.
Switzerland decided not to recommend mammograms when they concluded that they only reduce breast cancer death in one out of a thousand women, while the screening either does not affect non-breast cancer deaths or increases the risk by one in a thousand. In other words, they produce no benefit because you simply trade one cause of death for another (12).
For men, the problem is similar. Prostate cancer is the second most common cancer in men. But a Cochrane review of five controlled studies found that PSA screening for prostate cancer did not reduce the risk of death from prostate cancer or from any other cause. It did, however, lead to high rates of false positives, overdiagnosis and adverse events (13). In men who have had three or four PSA tests, 12-13% will have a false positive (14). False positives can lead to biopsies, and biopsies significantly increase the rate of death: 1.3% of men die within 120 days of having a biopsy compared to only .3% of men in the control group (15). So, PSA screening for prostate cancer actually increases the risk of harm and even death without providing any benefit.
For these reasons the U.S. Preventive Services Task Force now recommends that “the benefits of PSA-based screening for prostate cancer, as currently used and studied in randomized, controlled trials, do not outweigh the harms” (16). The U.S. Preventive Services Task Force is a panel of experts in prevention and evidence-based medicine that makes recommendations to the U.S. congress based on reviews of peer-reviewed evidence.
Lung cancer is the leading cause of cancer death in the world. But, unfortunately, the news is no better. The National Lung Cancer Screening Trial (NLST) of 553,454 heavy smokers found that CT scanning for lung cancer reduces the risk of overall mortality by only 0.46% (17). And, according to Prasad, et al. (18), even that minimal benefit may be exaggerated. When CT screening was compared to routine care in 4,104 healthy heavy smokers, there was a trend toward more deaths in the screening group: 2.97% of the screening group died versus 2.05% of the control group. There was evidence of overdiagnosis of lung cancer: 18% of people diagnosed with lung cancer by CT scan were victims of overdiagnosis (19). 39.1% of people had at least one positive CT scan, but 96.4% of them were false positives. (20).
An even bigger study undertaken by the U.S. Preventive Services Task Force produced equally discouraging results. The meta-analysis of 60,000 people who participated in randomized controlled studies showed that people who had CT scans did not live any longer than people in control groups (21).
A second meta-analysis included the NLST study discussed above and added two other smaller studies; however, neither of the smaller studies showed any benefit for CT scans for lung cancer (22).
Amongst men and women combined, colon cancer is the third most common cancer in the world. There are a variety of screening methods for colon cancer, but the one with the most evidence for efficacy is the fecal occult blood test. To test the efficacy of the fecal occult blood test, the Minnesota Colon Cancer Control Study followed 46,551 people for thirty years. At first, the results seemed more encouraging, but, at a closer look, the same problem appeared. There were less deaths from colon cancer in the screened group: 128 per 10,000 died in the screening group versus 192 per 10,000 in the control group. But when the researchers looked at the actual overall deaths, the advantage totally disappeared: there were two more deaths in the fecal occult test group than in the control group. There was no difference in mortality and no benefit to screening for colon cancer (23).
Though there is no benefit to occult blood screening, there is, once again, a cost. A meta-analysis re-analyzed three studies on fecal occult blood tests that included 245,217 people. Once again, though the risk of dying of colorectal cancer went down when people got occult blood tests, their risk of dying from something other than colorectal cancer went up. The cost in terms of non-colorectal cancer deaths balanced the benefit in terms of protection from colorectal cancer death so that there was a slight increase in deaths for people who were screened. The researchers concluded that the efficacy of fecal occult blood tests is uncertain and needs to be re-evaluated (24).
Endoscopic visualization (colonoscopy) of the colon is another screening option for colorectal cancer; however, surprisingly, there have been no randomized controlled studies of the efficacy of colonoscopy (25).
The recent research into screening for thyroid cancer is a startling reminder of the need to reevaluate the true benefits of cancer screening. Research into the four most common cancers—lung cancer, breast cancer, prostate cancer and colorectal cancer—reveals that screening does not improve overall survival for any of them despite the real possibility of harm.
Because the public is often told only of the benefit for prevention of the specific cancer screened while being kept from the cost of harm and even death from the screening, the public perception of cancer screening is often, unfortunately, exaggeratedly trusting and optimistic. The most optimistic results of estimates based on the actual studies do not even approximate the optimistic perceptions of the public, which inflate the benefits and discount the costs (18).
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