Can cancer be detected by general physical examination?

Early detection of cancer is hot. A basic situation is this: the treatment of cancer, at the intermediate and late stages, has not yet made any breakthroughs, except for a few types of cancer, such as breast cancer. So, a natural idea is to detect it at an early stage and treat it early.

However, cancer screening, especially early screening when autologous and asymptomatic, is still a very controversial area. This is mainly because early detection is difficult to study, the accuracy of existing methods is low, and the benefits to the person being examined are limited.

As far as I know, cancer is usually detected mostly due to the following conditions.

  1. feeling symptoms and discomfort and going to the hospital to get checked out.
  2. going to the hospital for examination of other diseases, and some kind of cancer is detected incidentally.
  3. Routine medical checkups, which reveal abnormalities and further examination reveals cancer.
  4. Targeted cancer checkups, like regular checkups, which reveal abnormalities.
    (Add: In case 5, you are a high-risk group for specific cancers, such as family history, long-term smoking, hepatitis virus carriers, etc., and need to be monitored regularly, which is another case)

For 4, there is no universal test, only specific test for a particular cancer, as @Jing Wai mentioned. The most common and commonly adopted ones are mammograms for breast cancer, pap smear for cervical cancer, PSA antibody blood test for prostate cancer, blood test and colonoscopy for colorectal cancer, etc.

From the medical point of view, of course, the problem is most serious when there are direct symptoms; the situation is least serious when cancer is found without any abnormality.

Therefore, in general, there is no big objection to cancer detected by direct symptoms, because it has already affected normal life, and most of the time it is in the middle or late stage, so it should be treated immediately. However, the most controversial ones are 2-4, that is, cancers with no abnormal sensation, and the controversy increases gradually from 2 to 4.

It is so controversial that I think it is impossible to give you a recommendation, but I can only provide some information to help you understand the complexity of the problem and know some basic knowledge about cancer, so that you can make your own decision.

Modern people talk about cancer, even the mildest is cancer.

However, cancer is not one disease, but many diseases. As @jinxi said, the same cancer can have very different mechanisms. In a sense, every tumor is different. A’s lung cancer and B’s lung cancer may not be the same, they just have the same or similar phenotype, but the pathogenic mechanism and genotype can be different. If they are different, it is possible that these cancers have different pathologies and different degrees of malignancy.

Take prostate cancer as an example.

It is now estimated that one in six American men will develop prostate cancer at some point in their lives. However, not all prostate cancer is malignant, and most of this cancer actually progresses very slowly. For example, autopsies performed on American soldiers who died during the Vietnam War revealed that many had microscopic prostate cancer in their 30s. Considering that most people do not get the disease until they are older, it is reasonable to believe that most of these cancers may also grow slowly and remain unknown even until death.

In fact, autopsies show that many people do die without knowing they have this cancer, and they do die unrelated to it. 1 in 3 men between the ages of 40 and 60 have prostate cancer, and by age 85, 3/4 have prostate cancer.

Similarly, breast cancer. Autopsies of women who die at age 80 show that 2/3 have breast cancer, but only 4% die from it. As with prostate cancer, most people live with the disease, don’t actually know they have cancer, and don’t die from it.

For the average person, I believe that most people’s ultimate concern is actually how long they will live, not whether they have cancer and if so, whether the cancer can be cured. So, what really worries the heart are the tumors that are malignant, lethal or immediately affect the quality of life.

However, it is well known that the more malignant the cancer, the faster it progresses, and it can take only a few months from the appearance of a true cancer to the onset of significant symptoms. The best window of time to treat this type of cancer may be only a few weeks, which in most cases is not enough to wait for any annual physical exam. And what a physical exam can detect is likely to be a slowly developing cancer.

Of course, we can trust science and now be able to detect cancer when it is really early and prevent it before it starts to get worse.

However, with what I know about this direction, there is still very little that medicine can do right now (2011).

First of all, as mentioned above, cancer is not a rare thing, and it is likely that you already have it in your body, as many tumors take more than a decade or more to become malignant (of course, they may hang themselves in the process, and it is not easy to grow a tumor). Nowadays, the examination technology is getting more and more sensitive, I really doubt that if you want to find your cancer, you can really find it by doing all kinds of tests. The result will be, so what if you find it?

Then let’s find it.

Since it is a screening, generally from the early screening (early screening) to start.

This is really hard to do.

For example, now that there is blood testing technology, a PSA antibody test can tell you if you have prostate cancer.

The idea of detecting cancer in the blood is approximately like this: there are cancer cells, and these cancer cells will emit specific molecules to the surrounding area, such as factors that promote blood vessel growth (cancer cells also need blood to give them nutrients), or cancer cells may be killed (many, after all, cancer cells are abnormal cells, and the immune system is not a freeloader, one will be killed), and these cancer cells may have special molecular components released after being broken down. After these cancer cells are broken down, some special molecular components may be released. These molecules enter the bloodstream, so that a special examination of the blood can reveal traces of the presence of these cancer cells.

It is common practice to compare the blood of a cancer patient with that of a normal person to see what the differences in composition are, and finally to find the most representative molecular components.

However, there is a logical problem here.

While the target of early detection is a so-called normal person whose body is in a symptom-free period but later develops a malignant tumor, the sample used to find this cancer-specific molecule is obtained from a person who definitely has cancer. For people who definitely have cancer, the cancer has already developed considerably, and at this time the tumor has many more important mutations than the early stage tumor, and it is likely that those early features are hidden in a myriad of molecules.

For example, I once compared the RNA expression of some colorectal cancer cells with normal cells and found that at least 1/3 of the genes were expressed differently, not to mention other differences. This is the difference between cancer cells and normal cells. It is indeed a bit of a needle in a haystack to find out the specific expression factors in early cancer cells from here.

To make matters worse, these early stage tumors have far fewer molecules that can be released into the bloodstream because they are small, which places a high demand on the sensitivity of the test.

In a recent study, blood samples collected several years ago from people who had a specific cancer in the follow-up pairs were analyzed, and it was found that in terms of early detection, the various expression features found in these recent years did not work, and the best one used was still the one from decades ago, with conceivable accuracy.

To add insult to injury, these cancer cells are not some heavenly visitors, and they can release molecules that many normal cells would release, so that errors are inevitable. Even a test like PSA has a high error rate.

However, we know that a PSA alone does not count; after all, a cancer diagnosis is confirmed by biopsy.

The problem here is that the accuracy of biopsy is far from what people think. For example, for prostate cancer, 20% of biopsies are inaccurate in determining the degree of malignancy (and worse, in healthy people, the biopsy itself increases the chance of getting the cancer).

Similar errors also occur in other cancers, such as melanoma. In one experiment, several pathologists were asked to produce what they thought were typical sections for other experts to examine, and the result was that even with these typical sections, one quarter of the cases were not uniformly recognized. At the top melanoma treatment center in San Francisco, each biopsy is reviewed by three doctors at the same time, and the decision is made jointly because some tumors, especially early ones, are difficult to diagnose.

So the early stage tumors we care about are even more problematic in terms of diagnosis (if you don’t have any symptoms, I suggest you must find more than two hospitals/doctors to help you diagnose and determine the treatment/observation plan.

With so many problems of this and that, what is the situation that leads to?

The situation is that these early tests for cancer may not help to prolong your life, and if they are misdiagnosed, can also make your quality of life much worse.

For example, the PSA test for prostate cancer mentioned above.

This is a fairly routine test. To date over thirty million men in the United States have had this test done. The general recommendation is that all men over 50 years of age should have this test done regularly.

However, the U.S. government’s United States Preventive Services Task Force is giving new recommendations on PSA this week. In data released last week, it said the test has no particular benefit, does not extend your life on average, and only adds to the pain of the treatment: In the two decades between ’86 and ’05, one million American men had surgery or chemotherapy for PSA, 5,000 died from the procedure, 10,000 to 70,000 had other serious surgical problems, half had red blood cells found in their semen, and 200,000 to 300,000 had red blood cells found in their semen. Red blood cells were found, and 200,000-300,000 people lost their sexuality.

And just two years ago, the same agency announced that mammograms, a common breast cancer screening, also had more negative than positive effects.

So, why is our society so keen on early cancer screening?

Actually, the problem is not only cancer, but in many other diseases as well, such as cardiovascular disease, diabetes, and so on.

In other words, society is constantly conveying the idea that a healthy life is the norm and anything less is dangerous and needs to be corrected. (In fact, if you ask me, unhealthy is the norm, such as headaches, nasal congestion, diarrhea, broken feet, small and large things that happen twice a day …… )

The result is that the more you go to the doctor, the more the doctor makes your illness look like (maybe it’s a term you’ve never heard), the happier you are. If the doctor says you’re not sick, you’re probably still not satisfied, right? (There is a study about this, which is very funny)

But there are two sides of the coin.

A misdiagnosis can be a case of not finding a disease, or it can be a case of not finding a disease.

What we have now is that most people would rather find a disease without a disease (with the idea that there is no harm in treating it) than find a disease without a disease.

Hospitals and pharmaceutical companies love this.

You want to find the disease, then set the normal indicators lower. What about the middle section?

Pre-xx disease! Scary, right?

Originally there is a disease to treat, but now people who are not sick also need to make regular check-ups, subhealthy people also need to take drugs (a certain cancer only tens of thousands of people a year, check-ups can be checked millions of millions of people ah, all money ah).

As a result, the important aspects, healthy lifestyle and life itself, are pushed back; checkups and treatments, which can make money, are pushed forward.

Tumors that may not develop or be felt until years later are now detected earlier with increasing sensitivity of clinical detection, so you can be treated earlier. You also become a cancer patient, walking the path of striving to be a cancer survivor.

It is important to acknowledge that the mortality rate of related cancers is declining due to the widespread rollout of early cancer screening. For example, the death rate from prostate cancer in the United States has dropped by 25% because of the widespread availability of PSA and advances in treatment. In contrast, in Denmark, where PSA screening is not as widely practiced, prostate cancer mortality has increased by 50% in recent years.

The controversy over early cancer screening is not whether they save cancer patients; every patient who is actually detected is a living testament. The controversy is over whether they over-treat and place an unwanted additional burden on most people. For example, some estimates say that for every breast cancer patient detected early, there are 2 – 10 misdiagnosed patients. If you insist on getting mammograms every year, the 10-year probability of misdiagnosis is over 20%. What is best for society is still a topic of discussion.

One final figure.

Without cancer, the average life expectancy in developed Western countries is estimated to increase by 4 years.

Only four years.

Put it in a developing country and the number would be even smaller.

And in the game of life, no one gets through it alive.

Sorry for the lack of specificity in any of the relevant literature, as it is a random comment.

If you are interested, see this book (which should be available for download).
H. G. Welch. Should I be tested for cancer? : maybe not and here’s why. University of California Press, Berkeley, 2004.