Cancer: the good news

Cancer, paradoxically, is a sign of survival success

Cancer is not on the increase.

The first thing to realize is that not only there is no cancer epidemic, but also that statistics indicate a constant reduction in both cancer death rate and incidence in the USA and in the developed world from the 1950s, when adjusted for age and smoking.

The problem with cancer in the West is sort of paradoxical. Cancer is in many ways a success story, a sign of our survival triumph. We have a cancer problem only because we are a highly successful civilization which has defeated the deadlies killers of the past, infectious diseases that used to decimate our populations.
For that reason, we live much longer.

There's a joke that goes like this. Asked if he feared the idea of getting older, a famous writer answered: no, if I consider the alternative.
We might paraphrase that as: the alternative to having a cancer risk as a society is worse.

Cancer is almost exclusively a disease of old age. So, when the population ages, it will die more of cancer. In 1900, young people were dying of tubercolosis, pneumonia, influenza and other infectious diseases. Today, when we have got to live until a much older age exactly because we do not die from those infections, and since we have to die of something sooner or later, we have to die more of heart disease and cancer.

So, when a population ages, more frequent cancer may be not a sign of any higher risk, but simply an indication of more people having survived infections and moved up into more cancer-risky age groups.

This problem is corrected by adjusting the cancer rates for age: basically, determining what the cancer rate would have been if the age distribution in the population had not changed.

When we correct for age, we find that there is still a 1 percent more people who die from cancer each year in the US.
Ah, here's the bad news, you may think. But no, the news is still good, because that slight increase in the annual cancer death rate has only one simple cause: past bad smoking habits, which are now changing but whose consequences are still being felt.
Today, the only type of cancer on the increase is lung cancer, and by far the largest part (91 percent) of lung cancer is due to smoking.

So, if we take the age-adjusted cancer rates and we remove the cancers caused by smoking, the result we get is a marked decline of almost 30 percent in cancer mortality from 1950 to 1998.

At the same time, we also die less of other causes, in particular cardio-vascular diseases, in the USA and in the developed world as a whole. Taken together, the evidence consistently shows that non-smokers have experienced decreasing overall cancer death risks as well as ever declining death rates from other diseases.

Cancer is mostly related to lifestyle choices and can be prevented

One of the hopeful messages from cancer research is that most of the cases of cancer are linked to environmental causes, especially lifestyle ones, and in principle can be prevented.

Two of the world's leading cancer researchers, the English epidemiologists Sir Richard Doll and Richard Peto, carried out one of the largest studies of the relative importance of various avoidable causes of cancer and wrote a seminal analysis in 1981, which still remains valid today and is the reference work for proportions of cancer attributable to various causes.
Diet causes the highest proportion of cancer deaths: 35 percent.
We know from many studies, especially of migrants, that our eating habits affect our cancer risk. Examples of this are breast and colon cancer, which are among the most widespread forms in the USA, rare in Japan but common among American Japanese.

The food we eat has changed considerably since industrialization: we eat more processed food, far more sugar, meat, dairy products and fat.
Increasing the amount of fat, salt, low-fiber and meat-based food we eat increases our risk of getting cancer.
Similarly, obesity and a higher intake of calories also increases the risk of our developing cancer.
On the other hand, eating both fruit and vegetables reduces cancer risk.
Changing our diet so that we avoid meat, fat and obesity and eat more fruit, vegetables and fibers would get rid of all food-related occurrences of cancer, i.e. reduce the frequency of cancer in the West by as much as 35 percent.

Tobacco is also a major contributor to cancer deaths: around 30 percent. Tobacco smoking is the cause of many cardiovascular diseases as well, overall causing about 20 percent of all deaths.

Infections, parasites, bacteria, viruses are responsible for 10 percent of cancer deaths. Sex-related factors and childbirth, 7 percent. Occupation, 4 percent. Alcohol is carcinogenic too, causing about 3 percent of cancer-related deaths. UV light from the sun, together with ionizing radiation from many sources, including cosmic rays, X-rays, radioactive radon seeping from underground, cause 3 percent of cancer deaths. Medicines and food additives, less than 1 percent each. Pollution from many sources, air, water, food contamination, about 2 percent.

So, we have a situation where at least 75 percent of the cancer risk stems from personal choices of eating, smoking, drinking and the like.

Every time this research has been carried out and repeated, the results have been the same.
A much quoted study about not just cancer deaths but all deaths, published in the Journal of the American Medical Association in 1993, which was then updated in 2004, "Actual Causes of Death in the United States", concludes that "smoking remains the leading cause of mortality. However, poor diet and physical inactivity may soon overtake tobacco as the leading cause of death."
At least 80 percent of the explained deaths are dependent on individual behavior, mainly tobacco, diet and activity patterns, alcohol consumption.

The latest report shows that the leading cause of cancer death for both men and women is lung cancer.
Prostate cancer is the leading cancer diagnosed overall in men in the United States and breast cancer is the most common form of cancer diagnosed in U.S. women.
Colorectal cancer, although not as widespread as the other three, is the fourth most common type of cancer, affecting both men and women. Physical inactivity is strongly linked to colorectal cancer, and dietary factors, especially low fiber intake.

Lung cancer

Of all cancers, the one with the heaviest occurrence in the USA is lung cancer, particularly male lung cancer.
For men, lung cancer has been the predominant type of cancer since 1953; for women, it became the most widespread form of cancer in 1986, surpassing breast cancer.

The growth in lung cancer is strongly linked to smoking.
We know from the two largest studies in the world, each involving more than a million people, that non-smokers have a very low and stable cancer rate.

Smoking increased dramatically over the first part of the 20th century. The consumption of cigarettes grew from 54 per person per year in 1900 to 4,345 in the 1960s, and has decreased since then to 2,261 in 1998: the same as in 1942.

If the two curves of US cigarettes consumption and lung cancer mortality rates are seen together, they illustrate dramatically and visually the massive effect of smoking.
Men started smoking early in the 20th century, peaking around 1960 with an average of over 16 cigarettes per day (averaged over all men including male non-smokers). The male lung cancer rate equally rose from about 5 to its peak of 75 per 100,000 men in 1991, declining thereafter (also including non smokers).
Women have never smoked as much as men, peaking in the mid-1970s at 9 cigarettes and decreasing thereafter. The female lung cancer rate has increased from 2.3 in 1950 to more than 34 per 100,000 women in 2000, and it has still not levelled out, although it seems likely to do so soon.

Tobacco is a major success story. The proportion of the U.S. population that smoke has been going down for several decades, and just within the last decade, lung cancer rates have also started to go down.

Breast cancer

Breast cancer is the second leading cause of cancer deaths in women today (after lung cancer) and is the most common cancer among women, excluding nonmelanoma skin cancers.

The age-adjusted incidence rate of breast cancer (number of new breast cancers per 100,000 women) increased by approximately 4% during the 1980s but leveled off to 100.6 cases per 100,000 women in the 1990s. The death rates from breast cancer also declined significantly between 1992 and 1996, with the largest decreases among younger women. Medical experts attribute the decline in breast cancer deaths to earlier detection and more effective treatments.

Established risk factors include increasing age, having a family history of breast cancer, having a first child after 30 years of age, never having given birth to a child, alcohol consumption, having higher income.

And, importantly, breast cancer risk increases with body weight. Obesity and lack of exercise play a major role, and obviously the type of diet can influence the condition of being overweight. In particular, high fat diets are a risk factor.

Prostate cancer

Prostate cancer is mainly a disease of old age: the median age for diagnosis is 72 years.
Research indicates in particular a stable connection between higher intake of animal fat and higher risk of prostate cancer.
On overview of the NIH (National Institutes of Health) of the US, one of the world's foremost medical research centers, states that "the evidence for an important role of diet in prostate cancer development has increased over the last decade. The risk of prostate cancer seems to be higher for men eating high-fat diets with few fruits and vegetables."

Equally, as in the case of breast cancer, the slight increase in prostate cancer is mostly caused by an increase in early detection.
That gives treatment a better chance and makes death rates decline.
Partly, there are more operations for benign prostate disease (or prostate changes), where asymptomatic prostatic tumors are found inciidentally.
Partly, new diagnostic techniques such as transrectal ultrasound guided needle biopsy, computer tomography, and the serum testing for prostate-specific antigen (PSA), mentioned below, have increased the detection rate.
Actually, when examining the prostates of men who had died at 70 from completely unrelated causes and with no clinical history of prostate cancer, researchers found that 25 percent had prostate cancer, indicating that there is a very large pool of possible - and potentially harmless - prostate cancers waiting to be discovered.
Nevertheless, the very increase in detection has generally led caused prostate cancer to be discovered earlier, consequently giving treatment a better chance and making death rates decline.

A fairly new testing method, the prostate-specific antigen (PSA) test, has been rapidly adopted since its introduction in 1987. This test has led to the discovery of many latent prostate cancers and consequently has created a much greater pool from which to misattribute the cause of death. A 1999 study from the National Cancer Institute indicates that this may be a major cause of the recent rise and fall of the death rate, while the PSA in the longer run is likely to decrease further the prostate cancer death rate.

  Health and nutrition