Some cancer screening is useless or even harmful.

Original Wang Chenguang returned to the park

At the end of each year, many institutions will organize collective physical examinations, and the unit will also spend money to give employees another additional benefit: increasing cancer screening programs. Today, the concept of "early detection and early treatment" of cancer is deeply rooted in people’s hearts, and this kind of "welfare" will undoubtedly be welcomed. As everyone knows, tumor screening is not completely beneficial.

Author | Wang Chenguang

At the end of last year, the author did an annual physical examination in the United States and consulted his family doctor about skin eczema and digestive tract symptoms (flatulence and nausea at that time). Shortly after the new family doctor retired from the army, after knowing the medical history and completing the physical examination items, he issued two referral letters, one for dermatologists and the other for gastroscopy.

According to the information in the referral letter, the author made an appointment for gastroscopy. On the day before the examination, the author received a phone call from the doctor in charge of gastroscope, and at the same time received system information with the same meaning. The general contents are as follows:

I am Dr. XX, and you are scheduled to undergo upper gastrointestinal endoscopy (EGD) on December 19th. I checked your chart. As a gastrointestinal doctor, I don’t think we should start with this procedure because it has its own risks and benefits, and according to the records of your family doctor, I don’t think this is the first thing we need to do. Your blood tests (including liver and blood cell count) are normal, so I won’t give you such an invasive test with the risk of surgery and anesthesia.

At the moment when gastroscopy screening has almost become the standard for physical examination of middle-aged people, such communication may be rare. 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 summed up in one sentence, that is, disease screening for healthy people, including cancer, cannot be implemented unconditionally.

The key to screening is to weigh the benefits and hazards.

Before discussing this problem further, we need to understand several similar concepts. This is also the first question that the author should ask whenever a friend sends me the examination results and asks me for advice: Is this the result of routine physical examination or the result of the examination items given by the doctor when he sees a doctor after symptoms? This problem involves the classification of inspections according to their purposes.

If you feel unwell to see a doctor, the examination prescribed by the doctor is not a screening, but a confirmed examination; If the purpose of the examination is to find high-risk factors of cancer, such as colonoscopy and cervical smear, and to intervene in advance or provide basis for regular examination in the future, it belongs to preventive screening, and the purpose is to find precancerous lesions that have not yet developed into malignant stage; If the purpose of the examination is to find asymptomatic cancer tissues, such as mammography, and provide evidence for further diagnosis (biopsy) and treatment (surgery), this is an intervention screening. The latter two are screening programs based on healthy people.

As far as cancer screening is concerned, its purpose is to find out before normal tissues become cancerous or cancer tissues cause symptoms, but this is not the whole content of cancer screening. To be valuable for screening certain or some cancers, a technical means needs to meet three conditions at the same time: first, it is a prerequisite to be able to find precancerous lesions or cancer tissues as early as possible; Secondly, it is to reduce the chances of people who are screened regularly getting cancer or dying of cancer, which is the purpose; Finally, the benefits of screening must outweigh the harm, which is the key point.

Considering the screening content as the key point is based on two facts: some screening is invasive and will lead to bleeding or other injuries; No screening method can be 100% accurate. False positive results are likely to be accompanied by over-diagnosis and over-treatment, while false negative results may make people lose their vigilance against subsequent symptoms.

Next, based on these two facts, the author will talk about which screening is beneficial or useful, and which is not and may be harmful.

There are actually very few types of necessary cancer screening.

Except for high-risk people with a family history of cancer, some special screening programs are applied. There are not many cancer screening programs for healthy people. The following cancers can be screened, but only the suggested methods are meaningful.

Breast X-ray examination for specific groups is the best way to find breast cancer early. Specific groups are first of all age-limited groups. Different guidelines give different ages for the first screening, and the age between 45 and 50 covers almost all the guidelines for the first screening. This is because the incidence of breast cancer in women before 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 had mammography before the age of 45.

Pap test can find abnormal cells that may become cancerous in the cervix, while HPV test can confirm the virus (human papillomavirus) that causes these cell changes. The guidelines given by different professional institutions are similar in the age of starting screening and testing items, which are basically as follows: the age is between 21 and 29, and they receive Pap smear examination every three years; Women aged between 30 and 65 can choose one of the following three options: continue to have Pap smear every 3 years; HPV testing and screening every 5 years; Pap smear examination and HPV detection screening were performed every 5 years.

Colorectal cancer almost always develops from precancerous polyps of the colon or rectum. Colonoscopy screening can find polyps and remove them before they become cancerous. For ordinary healthy people, the first screening is recommended at the age of 50. If abnormal hyperplasia such as polyps is not found, it can be screened again after 10 years. If a few polyps are found, removed and pathologically benign, they can be screened again after 5 years.

Low dose CT for lung cancer screening. It is suggested that the screening population should be those aged 55 to 80, who have a history of smoking and have given up smoking for no more than 15 years.

In addition to the above, all other types of cancer, such as ovarian cancer, pancreatic cancer, prostate cancer, testicular cancer and thyroid cancer, have no specific benefits. Not only is it useless, but it has known definite harm. Any screening that does not meet the above recommendations is excessive.

Sometimes, overtreatment is more harmful than cancer.

Prostate cancer screening program may appear in a considerable proportion of middle-aged men’s physical examination reports in China. Next, take prostate cancer screening as an example to see that some cancer screening programs 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 this screening project, the "achievements" were remarkable, and a large number of suspected prostate cancer patients were screened out. A variety of imaging and even biopsy diagnostic tests followed, some people were excluded from prostate cancer, some people were diagnosed with prostate cancer and underwent surgical resection and a series of subsequent treatments.

However, controversy ensued. Some experts believe that PSA leads to overdiagnosis and treatment, and some experts believe that this screening can help some patients to find and treat prostate cancer early, which can save lives.

Right and wrong? Evidence-based medicine has played a decisive role here. With the expansion of screening population and the accumulation of data, professional organizations organized experts to judge the data, and quickly reached two main conclusions: the increase of PSA level of healthy people participating in screening was more caused by benign prostate diseases, and most men with increased PSA level did not suffer from prostate cancer; A few patients who are subsequently diagnosed with prostate cancer may never threaten their lives.

Therefore, professional organizations quickly revised the previous guidelines for screening prostate cancer, and did not recommend PSA as a single indicator for cancer screening of healthy people, only for auxiliary diagnosis or for monitoring the prognosis of prostate cancer patients.

What are the factors that make PSA unsuitable as a screening project for prostate cancer? There are roughly three factors, which are also applicable to cancer screening programs provided by most current medical institutions.

The first is the lack of specificity in testing. As mentioned earlier, an elevated PSA level does not necessarily represent prostate cancer. Other prostate diseases such as prostatitis and prostatic hyperplasia may also lead to the increase of PSA, and this situation is higher in healthy people without prostate symptoms. This lack of specificity makes PSA test prone to misdiagnosis and overdiagnosis in the screening process.

Secondly, PSA test can’t distinguish between chronic and invasive prostate cancer. Many men suffer from chronic prostate cancer in their old age, but this kind of cancer usually grows slowly and does not pose a threat to life. Using PSA as a screening index may lead to overdiagnosis and overtreatment, which will bring unnecessary risks and burdens to patients.

Finally, the screening results and subsequent medical actions will cause physical and psychological troubles to patients. Although early diagnosis and early treatment can save some patients’ lives in theory, it seems to be true for individual patients. However, the follow-up medical measures 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 if patients are finally 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 will not die of prostate cancer.

In contrast, once the screening is positive and diagnosed, 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 urgency, dysuria, diarrhea and rectal pain, and long-term side effects include erectile dysfunction, rectal bleeding and urethral stricture.

You shouldn’t eat a free lunch.

The benefits of tumor screening are often exaggerated, while its risks are often diluted or ignored. As individuals, we all hope that we are the one who saved our lives by early detection and early treatment, but it is easy to ignore the fact that the result of participating in screening is more likely to be over-diagnosed.

The annual physical examination package provided by many units for employees contains a number of cancer screening projects, and many people check it with the mentality of "free, no white check"; There are also many people who think that screening is better than no screening, and more screening is better than less screening. In such an atmosphere, it takes courage for a person to refuse screening when colleagues and friends around him are doing it.

All these people don’t realize the fact that physical examination is also a medical act. Being positive for cancer screening is no different from being diagnosed with cancer in medical essence.

On the other hand, people who do cancer screening do not want their screening results to be positive, but screening positive is the significance and value of a screening (in order to achieve early detection and early treatment).

Because cancer screening may "trigger" the subsequent continuous medical behavior, before you go to do a necessary cancer screening project that is not mentioned above, you might as well ask yourself: Can I face the positive result calmly?

The author is a doctor of biology. He used to be a researcher at Sidney Kimmel Cancer Center of Thomas Jefferson University, an associate professor in the Department of Cancer Biology and a professor at Union Medical College. He is currently engaged in the research and development of anti-tumor drugs.

This paper is supported by the popular science China starry sky project.

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

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

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Original title: "Some cancer screening is useless or even harmful"

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