I had a grand aunt, an unmarried lady. She was an amazingly healthy old woman. At the age of 50, she had an ultrasound of the neck done, as part of a work-up for a sore throat. The throat cleared after a few days. It was some minor infection. But the ultrasound scan picked up a small nodule or swelling in her thyroid gland, and a needle aspiration biopsy showed it as Papillary Cancer of the thyroid gland. It was less than a centimetre in size. She was very upset. My father was her chief adviser and friend. He showed her to some specialists and she was put on regular tablets. I was just a kid at the time. I heard the entire thing from my grand aunt, who regaled listeners with this story, whenever any unfortunate relative was within hearing distance.
She died, years later, of what can only be considered old age. She was 88. She had pneumonia. When I visited her on one of her last days, she told me again of the wonderful tablets that had saved her life. She pointed to the bedside shelf.
“It is in there,” She said.
I had got into MBBS by then. I got curious. I opened the shelf and got the bottle of tablets out, and read the label.
It was an uncommon multivitamin brand. The wonder drug!
Cancers are on the rise! The hype is deafening. At the time of writing this, here, in Kerala, the media is going crazy about the “sudden” epidemic of cancer. Kerala has a much higher incidence than other states. How is that possible? We have the best health indicators otherwise. Our average lifespan is the best in India. Infant mortality is minuscule. Infectious diseases are lower.
The only answer must be – Westernisation. Urbanisation and air pollution. Hormones in our chicken. Pesticides in our vegetables and the industrial effluents in the drinking water are killing us through that Emperor of all Maladies – cancer. That is how the TV channels put it.
Let us look to the West then. Cancer incidence has indeed been increasing in affluent countries. It is competing well with cardiovascular disease. In the United States, it is second in the scourges that bring death. In UK and Canada, it is the number one cause of death. In India and less developed countries, cancer incidence and mortality is comparatively very low. See – we have an epidemic on our hands. But what are the causes?
This is a classic case of how one can be misled by statistics if one is not critical enough. At the beginning of the century, the global lifespan was around 40. At the time of independence, Indians had an average lifespan of about 45, which has now increased to 65. While in the West, from a mere 60 in the 1960s, an average person is expected to live to an amazing 80, or even 85. Kerala is nearing these numbers. It is not only that. For many European countries, the demographic transition is over. They have more number of older people in the population. India is a young country. The percentage of old men and women are much less.
Cancer rates are measured by Incidence and Mortality rates. Incidence is the number of new cases diagnosed per year per, say, thousand people. Mortality rate is the number of people dying from cancer as a proportion of total deaths.
Do you see what I am getting at? When the proportion of old people rises, the Incidence of diseases commoner in old age rises. When deaths due to diseases like childhood illnesses, accidents and infections like tuberculosis falls, the mortality rate due to cancer, heart disease, etc. rises. This is somewhat true for most lifestyle diseases. Most of them get common with increase in age. But this is most true for cancer.
That is because all the commoner cancers are essentially like degenerative diseases of old age. There are some childhood cancers, and of young adulthood, like some Lymphomas, Leukemias, Sarcomas and the like, but they are like exceptions to the general rule.
Cancers of the lung, prostate cancer, breast cancer, and cancers of the stomach, colon and rectum – these are the main causes of cancer-related disease load in most countries. Cancers of the mouth, throat, larynx, food pipe, and the cervix in women are much more common in countries like India, and they are largely preventable.
It is estimated that fully one-third of cancers are preventable, by avoiding smoking, chewing tobacco and arecanut and excess alcohol. These are mainly lung, mouth, throat, larynx and food pipe cancers. The incidence of all these cancers is not increasing and is declining in some countries due to aggressive campaign against these bad habits.
So we come to the stunning conclusion that almost all the rise in cancer prevalence is due to people living long. Age is the number one risk factor for most common cancers. As we become older, the chance that we may fall prey to the disease rises exponentially. Robert A. Weinberg, an expert, put it like this – “If we lived long enough, sooner or later, we all would get cancer.”
Some cancers of the thyroid are a classical example. Most humans, by the age of 50 will have nodules in their thyroids, if you scan their necks. Many may be small cancers. In fact, some studies suggest that up to 20 to 30 per cent of the population may be having small cancers that are less than a centimetre in size. Modern guidelines suggest that there is no need to biopsy these nodules, unless specific criteria are met. The vast majority of these very small cancers do not progress at all, or do so, very slowly. Some do become dangerous, however.
Prostate cancer is a classic case that illustrates this well. It is a disease of old age. It is usually a very slow-growing cancer. Some experts are of the opinion that if we do autopsy studies of all men dying of whatever cause in their nineties, most of their prostates will be hiding small toffee-sized cancers.
A few decades ago, lung cancer in the developed world and throat-related ones in the rest were the most prevalent ones among males. Now, all over the developed world, it is prostate cancer that is number one. The reasons are clear. Declining tobacco use (this decreases lung cancer), increasing life spans and increased medical surveillance like ultrasound scans that leads to more cases to be discovered are the chief causes. After breast cancer, thyroid cancer is rapidly showing an increase,
The truth can be brought out by something called “age-adjusted mortality rates”. This one calculates the mortality rate for a particular age only. This takes off the lifespan effect. When you look at the age-adjusted mortality rates, it is seen that they have been falling for most cancers all over the world.
Some cancers, like thyroid cancer, seem to be on the increase. This is thought to be mainly due to better early detection by the widespread availability of tests like ultrasound scanning.
Does lifestyle have any influence on cancers at all? Certainly. Smoking, chewing tobacco, and alcohol is responsible for one-third of the cancer load. The main cancers that can be prevented to an extent are those of the lung, throat, mouth, wind pipe and food pipe.
What about the others?
There is some evidence that a regular intake of fruits and vegetables have a protective effect against some cancers, like those of the colon and rectum. Increased body weight has been linked to an increase in cancer incidence. Reneham and Tyson published a meta-analysis of 141 articles related to Body Mass Index and cancer incidence. They found that many cancers like breast, colon, rectum, food pipe, etc. are significantly associated with increase in Body Mass Index. The fatter you are, there is a slightly increased chance of getting many cancers. The effect is slight. It is far less than, say, the relationship between weight and heart disease or diabetes. It is still not clear why there is a relationship at all. It may be due to a curious nexus between physiological ageing and less food. So ultimately, even this effect may be related to age after all.
There is some evidence to link environmental air pollution and lung cancer. This was suggested in a recent study. As for pesticides and other pollutants, apart from certain specific occupational exposures, the evidence has been slight, surprisingly. It turns out that we may not be dying out due to cancers brought on by environmental pollution, due to chemicals after all. The effects are grossly exaggerated.
Main photograph by Ju KI via Flickr.
