How can we get a reliable cancer screening that can cost thousands of dollars?

At the end of each year, many institutions organize collective physical examinations, and the units will also spend money to give employees another additional benefit: adding tumor screening programs. Today, when the concept of "early detection and early treatment" of cancer is deeply rooted in people's minds, this "benefit" will undoubtedly be welcomed. However, tumor screening is not entirely beneficial and harmless.

Written by | Wang Chenguang

At the end of last year, I had an annual physical examination in the United States and consulted my family doctor about skin eczema and digestive symptoms (such as bloating and nausea at the time). The new family doctor had just retired from the military. After understanding the medical history and completing the physical examination, he issued two referral letters, one to a dermatologist and the other to recommend a gastroscopy.

According to the information on the referral letter, I made an appointment for a gastroscopy. The day before the examination, I received a call from the doctor in charge of the gastroscopy, and at the same time received a system message with the same meaning, which roughly stated as follows:

I am Dr. XX and you are scheduled for an upper gastrointestinal endoscopy (EGD) on December 19. I have reviewed your chart and as a GI physician, I do not think we should start with this procedure as it has its own risks and benefits and based on your family physician's notes, I do not think it is something we need to do first. Your blood work (including liver and blood counts) is normal, so I will not perform this invasive test on you with the risks of surgery and anesthesia.

At a time when gastroscopy screening has almost become a standard physical examination for middle-aged people, such exchanges may be rarely encountered. On the contrary, domestic medical institutions often actively advocate and recommend various screening programs. Why did this specialist give such advice? The reason can be summarized in one sentence, that is, disease screening for healthy people, including cancer, is not unconditionally implemented.

The key to screening is to weigh the benefits and harms

Before we discuss this further, we need to understand a few similar concepts. This is also the first question I ask when my friends send me their test results and ask me for advice: Is this the result of a routine physical examination, or the result of a test prescribed by the doctor when I went to the hospital after I had symptoms? This question involves the classification of tests according to their purpose.

If you feel unwell and go to the doctor, the examination prescribed by the doctor is not a screening, but a confirmatory examination; if the purpose of the examination is to find high-risk factors for cancer, such as colonoscopy, cervical smear, etc., and to intervene in advance or provide a basis for regular examinations in the future, this is a preventive screening, the purpose of which is to find precancerous lesions that have not yet developed into the malignant stage; if the purpose of the examination is to find cancerous tissues that are asymptomatic, such as breast mammography, to provide a basis for further confirmatory examinations (biopsy) and treatment (surgery), this is an interventional screening. The latter two are screening projects based on healthy people.

As far as cancer screening is concerned, its purpose is to detect normal tissue before it becomes cancerous or before cancer tissue causes symptoms, but this is not all there is to cancer screening. For a technical means to be valuable in screening for a certain type or certain cancers, it must meet three conditions at the same time: first, it must be able to detect precancerous lesions or cancer tissue early, which is the premise; second, it must reduce the chances of people who undergo regular screening getting cancer or dying from cancer, which is the purpose; and finally, the benefits of screening must outweigh the harm, which is the key point.

The focus on screening content is based on two facts: some screening is invasive and may cause bleeding or other injuries; no screening method can be 100% accurate, and false positive results may lead to overdiagnosis and overtreatment, while false negatives may make people lose vigilance against subsequent symptoms.

Next, based on these two facts, I will discuss which screenings are beneficial or useful, and which are unhelpful and potentially harmful.

Few types of cancer screening are necessary

Except for some special screenings for high-risk groups such as those with a family history of cancer, there are not many cancer screenings in healthy people's physical examination programs. The following types of cancer can be screened, but only the recommended methods are meaningful.

Mammograms for specific groups are the best way to detect breast cancer early. First of all, specific groups are age-restricted groups. Different guidelines give different recommended ages for the first screening. The age range of 45-50 years old covers almost all guidelines for the first screening. This is because the incidence of breast cancer in women under the age of 40 is very low, about 15 cases per 100,000 people. For women over the age of 65, there are nearly 450 cases per 100,000 people, and the risk is 30 times higher. Many women in China may have undergone mammograms during physical examinations before the age of 45.

The Pap test can detect abnormal cells in the cervix that may become cancerous, while the HPV test can confirm the virus (human papillomavirus) that causes these cell changes. The guidelines given by different professional organizations are similar in terms of the age to start screening and the tests to be tested, which are basically as follows: Women aged 21 to 29 should undergo a Pap smear every 3 years; women aged 30 to 65 can choose one of the following three options: continue to have a Pap smear every 3 years; have an HPV test screening every 5 years; have a Pap smear and HPV test screening every 5 years.

Colorectal cancer almost always develops from precancerous polyps in the colon or rectum. Colonoscopy screening can detect polyps and remove them before they become cancerous. For healthy people, the first screening is recommended at age 50. If no abnormal growths such as polyps are found, the screening can be repeated 10 years later. If a few polyps are found, removed and pathology shows benign, the screening can be repeated 5 years later.

Low-dose CT is used for lung cancer screening. The recommended screening population is those aged 55 to 80 years who have a history of smoking and have quit smoking for no more than 15 years.

In addition to the above types, screening for all other types of cancer, including ovarian cancer, pancreatic cancer, prostate cancer, testicular cancer and thyroid cancer, has no specific benefit. Not only is there no benefit, but there are known clear harms. Any screening that does not meet the above recommendations is excessive.

Sometimes overtreatment is worse than cancer itself

Prostate cancer screening items may appear on the physical examination reports of a considerable proportion of middle-aged men in China. Next, using prostate cancer screening as an example, we will see that some cancer screening items are useless or even harmful.

In the early 1990s, prostate-specific antigen (PSA) was included in the physical examination program of American medical institutions as a means of prostate cancer screening. In the first two years of the implementation of this screening program, the "results" were remarkable, and a large number of suspected prostate cancer patients were screened out. Various imaging and even biopsy diagnostic tests followed, and some people were ruled out of prostate cancer, while some were diagnosed with prostate cancer and underwent surgical resection and a series of subsequent treatments.

But controversy arose. Some experts believed that PSA led to overdiagnosis and overtreatment, while others believed that the screening allowed some patients to detect and treat prostate cancer early, thus saving lives.

Who is right and who is wrong? Evidence-based medicine plays a decisive role here. As the screening population expands and data accumulates, professional institutions organize experts to analyze the data and quickly come to two main conclusions: the elevated PSA levels of healthy people participating in the screening are more likely to be caused by benign prostate diseases, and most men with elevated PSA levels do not have prostate cancer; for a small number of patients who are subsequently diagnosed with prostate cancer, prostate cancer itself may never threaten the patient's life.

Therefore, professional organizations quickly revised the previous guidelines that included PSA in prostate cancer screening. PSA is no longer recommended as a single indicator for cancer screening in healthy people, but only for auxiliary diagnosis or for monitoring the prognosis of prostate cancer patients.

What factors make PSA unsuitable as a prostate cancer screening program? There are roughly three factors, which also apply to the vast majority of cancer screening programs currently provided by physical examination institutions.

The first is the lack of specificity of the test. As mentioned earlier, an elevated PSA level does not necessarily mean that you have prostate cancer. Other prostate diseases such as prostatitis and prostate hyperplasia may also cause elevated PSA levels, and this condition is more common in healthy people without prostate symptoms. This lack of specificity makes PSA testing prone to misdiagnosis and overdiagnosis during the screening process.

Second, the PSA test cannot distinguish between chronic and aggressive prostate cancer. Many men develop chronic prostate cancer in old age, but this cancer usually grows slowly and does not pose a threat to life. Using PSA as a screening indicator may lead to overdiagnosis and overtreatment, bringing unnecessary risks and burdens to patients.

Finally, the screening results and subsequent medical treatments will cause physical and psychological distress to patients. Although in theory early diagnosis and early treatment can save the lives of some patients, this seems to be true for individual patients. However, the subsequent medical treatments based on PSA screening results are overdiagnosis and may lead to overtreatment for more people in the group. This conclusion is based on a set of data: Even for patients who are eventually diagnosed with prostate cancer, about half will not show symptoms for the rest of their lives, and 80% of patients who die within 15 years of diagnosis do not die from prostate cancer.

In contrast, once the screening is positive and the diagnosis is confirmed, it is often difficult for patients to refuse treatment, and the adverse reactions of radical prostatectomy include perioperative complications, erectile dysfunction and urinary incontinence. Radiotherapy can cause acute toxicity, leading to urinary urgency, dysuria, diarrhea and rectal pain, and long-term side effects also include erectile dysfunction, rectal bleeding and urethral stenosis.

A free lunch may not be worth eating

The benefits of cancer screening are often exaggerated, while its risks are often downplayed or ignored. As individuals, we all psychologically hope that we are the ones whose lives are saved by early detection and early treatment, but we tend to ignore the reality that the result of participating in screening is more likely to be overdiagnosed and treated.

The annual physical examination packages provided by many units to their employees include multiple cancer screening items. Many people go for the check-up with the mentality of "it's free, it's a waste not to get checked". There are also many people who think that it is better to check than not to check, and it is better to check more than less. In such an atmosphere, for those cancer screenings that have formed a public "consensus", when colleagues and friends around are all doing it, it takes courage for a person to refuse screening.

All of these people fail to realize one fact: physical examinations are also medical procedures, and there is no difference in medical nature between a positive cancer screening and a person being diagnosed with cancer.

On the other hand, no one who goes for cancer screening hopes that their screening result will be positive, but a positive screening result is the meaning and value of the screening (to enable early detection and early treatment).

Since cancer screening may "trigger" subsequent medical procedures, before you go for a necessary cancer screening program that is not mentioned above, you might as well ask yourself: Can I face a positive result calmly?

The author of this article is a PhD in biology. He has been a researcher at the Sidney Kimmel Cancer Center of Thomas Jefferson University, an associate professor in the Department of Cancer Biology, and a professor at Peking Union Medical College. He is currently engaged in the research and development of anti-tumor drugs.

This article is supported by the Science Popularization China Starry Sky Project

Produced by: China Association for Science and Technology Department of Science Popularization

Producer: China Science and Technology Press Co., Ltd., Beijing Zhongke Xinghe Culture Media Co., Ltd.

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