According to reports, on July 23, Japanese writer Keigo Higashino passed away from colorectal cancer at the age of 68. Higashino is the author of numerous bestselling novels such as The Devotion of Suspect X, Journey Under the Midnight Sun, and Miracles of the Namiya General Store, and many readers felt his death came very suddenly.
Colorectal cancer is one of the most easily detectable cancers in its early stages, and treatment for early‑stage colorectal cancer is relatively straightforward. If it had been discovered a little earlier, could Higashino’s life have been prolonged? Can other cancers also be detected through early screening?
Early cancer screening is, in recent years, one of the most theoretically promising and fastest‑advancing fields. However, it is not a panacea; it is still a developing technology with many shortcomings. Even when they all bear the name "cancer", different cancers vary greatly, and cancer screening cannot be reduced to a single standard line.
In today’s post, we will introduce you to the nature, types, scope of application, and limitations of cancer screening, so as to provide you with as objective a reference as possible when deciding whether to undergo screening.
1. Cancer screening: nipping it in the bud
The U.S. Centers for Disease Control and Prevention defines cancer screening as "checking your body for cancer before you have symptoms." "No symptoms" does not mean "no cancer," because cancer is not like food poisoning, which can cause major disruption within three to five hours. Except for a small subset of acute tumours that grow rapidly and draw attention, most tumours are adept at growing silently and stealthily. A tumour only one or two centimetres in diameter may have been lurking in the body for several years.
During the period when the tumour is biding its time, if it is not located near nerves or blood vessels, it does not cause much trouble. By the time the patient feels discomfort and goes to the doctor for imaging, the tumour has often grown large enough to impair normal physiological functions, thus triggering symptoms.
Cancer screening is an examination carried out during the window between "the tumour has started" and "the tumour is causing trouble." The best outcome is, of course, finding no tumour; if a tumour is found, it can be attacked while still small, using medical means to try to eliminate it completely – the difficulty of treatment and corresponding survival rates differ greatly between early‑ and late‑stage cancers. For example, for colon cancer, according to U.S. statistics from 2006–2012, the five‑year relative survival rate for localised colon cancer is over 90%, whereas for regional cancer it drops to about 70%, and for distant metastatic cancer the survival rate is only around 10%.
Cancer screening aims to nip the problem in the bud, intercepting tumours at an early stage to improve patient survival. The main screening methods currently used include routine physical examinations (e.g., palpation to find lumps in breast and testicular cancers), laboratory tests (checking blood, stool, or other body fluids for tumour markers), and imaging of tissues (various CT, X‑ray, MRI, etc.).
2. Only a few cancers are worth screening – colorectal cancer is one of them
The U.S. Centers for Disease Control and Prevention, referring to the report of the U.S. Preventive Services Task Force (USPSTF), recommends that for breast cancer, cervical cancer, colorectal cancer, and lung cancer, certain age groups and populations should be screened; for some other cancers, such as prostate cancer and ovarian cancer, screening is not necessarily recommended. The following cancers, when detected early, have relatively good prognoses. At present, only these few are worth screening.
Colorectal cancer: strongly recommended for certain age groups
Colonoscopy for colorectal cancer is not gender‑specific. It uses a flexible tube with a camera at the tip inserted into the intestine, allowing the doctor to visually inspect the inside of the bowel; if polyps or abnormal tissues are found, they can be removed immediately. Over the past few decades, colorectal cancer mortality has dropped by more than 40%, and many believe that early screening has played a role (though improvements in treatment and changes in lifestyle may also contribute).
The USPSTF recommends that people aged 50–75, regardless of gender, undergo colonoscopy every ten years, with a Grade A recommendation; for those over 75, because colonoscopy carries certain procedural risks, the recommendation is Grade C. Those with a family history of colorectal cancer should start screening earlier and more aggressively.
Colonoscopy is not the only screening method for colorectal cancer. Other options include faecal occult blood testing, barium enema, stool DNA testing, and more, usually performed every three to five years. These can be used at the discretion of the physician and patient, complementing each other.
According to the National Health Commission of China Colorectal Cancer Diagnosis and Treatment Standards (2020 Edition): Screening for colorectal cancer among people over 50 and high‑risk groups in Guangzhou, Shanghai, Tianjin, and Beijing has shown that the incidence continues to rise, but screening has improved early diagnosis rates and reduced mortality. The main approach involves identifying high‑risk individuals based on age, family history, faecal occult blood tests, etc., followed by endoscopic screening.
The 2024 Expert Consensus on Colorectal Cancer Screening in Chinese Community Residents recommends that individuals at average risk begin initial screening at age 45 and generally stop at age 75.
Breast cancer: recommended for certain age groups
It has been reported that, due to the widespread adoption of early detection, the death rate for female breast cancer patients in the United States dropped by 38% from its peak in 1989 to 2014 – based on the U.S. population, this means that nearly 300,000 women’s lives can be credited to breast cancer screening. Yet even so, breast cancer screening is not a one‑size‑fits‑all approach.
The USPSTF‑recommended screening is mammography, which uses low‑dose X‑rays to image the compressed breast to detect lumps. For women aged 50–74, screening every two years is recommended at Grade B (moderately recommended, slightly below Grade A). For younger women, aged 40–49, the situation is more complex, with a Grade C recommendation, meaning the decision should be made jointly by the doctor and patient. This is because false positives (i.e., reporting a tumour when there is none) are more common in younger women than in older ones; about one in ten abnormal findings turns out to be a false alarm. A false positive not only causes psychological distress but may also lead to overtreatment, doing more harm than good. Therefore, women with a family history or who have been found through sequencing to carry susceptibility genes may discuss with their doctors whether to be screened every two years. For these individuals, MRI might also be added, and vigilance should begin at an even younger age (after 30).
Cervical cancer: strongly recommended for certain age groups
For cervical cancer, the USPSTF recommends that women aged 21–65 have a Pap smear every three years (Grade A). HPV testing can also be performed, as HPV has a strong positive correlation with cervical cancer. HPV vaccines are now available, and eligible women of appropriate age may consider vaccination. For women under 21 or over 65, and for those who have undergone a hysterectomy, the recommendation is Grade D (not recommended).
Lung cancer: recommended for certain populations
A major cause of lung cancer is smoking; in the United States, 80% of lung cancer deaths are attributable to smoking history. If detected and treated early, the outcomes can be significantly better. The USPSTF recommends that people aged 55–80 with a heavy smoking history (one pack per day for 20 years, or two packs per day for 10 years), who are still smoking or have quit within the past 15 years, undergo a low‑dose spiral CT scan every year, with a Grade B recommendation.
Why other cancers are not recommended for screening:
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The tumour markers currently used lack sufficient specificity. If the accuracy of the markers used to confirm the presence of a tumour cannot reach an acceptable level when distinguishing between normal tissue, benign tumours, and malignant tumours, then the test results have little reference value.
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Some screening methods may produce false negatives (cancer present but not detected) or false positives (cancer reported but not actually present), doing more harm than good.
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Some tumours grow very slowly and often occur in the elderly; if detected and then treated invasively, the burden on the patient may outweigh the potential harm of leaving them alone.
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Even if detected, there may be no good therapeutic options available; in that case, screening or not makes little difference.
3. Is genetic testing for cancer reliable?
It should be noted that there are other organisations in the United States that provide recommendations on cancer screening, such as the American Cancer Society (ACS), which focuses on cancer, while the USPSTF covers a wide range of diseases. Their recommendations on cancer screening are not entirely consistent, and it is hard to say which is more reliable. However, because screening tests rated A or B by the USPSTF are covered by medical insurance, their recommendations have become the screening guidelines for most Americans. The situation in China is different from that in the United States, and specific practices should follow doctors' advice.
Is genetic testing for cancer, which is often mentioned, feasible? Many people follow the example of Angelina Jolie, who underwent genomic sequencing because of her family history of breast cancer, found that she had a higher risk of developing breast cancer, and therefore had her breasts removed to prevent it.
In fact, genetic testing at this stage is still very preliminary. Limited by genetics' understanding of the human genome, it cannot predict your life story just by extracting DNA from a few oral epithelial cells. Such testing currently has guiding significance for only a handful of diseases, and what it can provide is a probability of "whether you will develop cancer", not whether you "currently have cancer".
As a result, the U.S. Food and Drug Administration (FDA) has had a wavering attitude towards genetic sequencing over the years – the commercial genetic testing company "23andMe" was initially allowed to provide customers with disease risk information derived from genomic sequencing results, but later the FDA prohibited that, only permitting them to provide ancestry information. Then in 2019, the FDA again allowed them to provide disease information, but still limited to diseases with clear genomic associations, such as Alzheimer's and Parkinson's.
Like cancer treatment, early detection of cancer in a general sense remains a medical challenge; even the causes of cancer are not fully understood. Therefore, the effectiveness and applicability of cancer screening still need further development, and more screening is not always better.
Fortunately, there is still some clear information about cancer: stay away from clearly carcinogenic substances such as tobacco, alcohol, and betel nut; and once cancer is diagnosed, actively cooperate with treatment. In the hundreds of years since the birth of modern medicine, diseases that once claimed countless lives have gradually been conquered. Today's incurable diseases may also be conquered soon. Until that day comes, we will not stop our efforts to protect our health.
