Why are so many people getting cancer now?

[nec209]

It was not like this before!!! But now they say 1 in 4 people in US will get cancer and in the UK 1 in 3 will get cancer. They say if it continues in the UK in the future 1 in 2 people will get cancer.

 

Why is cancer on the rise? What is causing this? Why was it not like this before say 50 years ago, 100 years ago or even 200 years ago?

 

 

[pavelcherepan]

In a nutshell all is because now we have better diagnosis technologies and generally longer life expectancy giving more time for cancer to occur.

It takes a while in order for DNA replication errors to accumulate to start growth of malignant tumor and a bit of bad luck too, so if your life expectancy is low you probably won't live long enough for cancer to appear, although it still might happen.

 

Also keep in mind that majority of those cancers would be breast and prostate cancers which have efficient diagnosis methodologies (if not a bit unpleasant) and chances of survival are high.

 

https://en.wikipedia.org/wiki/Prostate_cancer

https://en.wikipedia.org/wiki/Breast_cancer

Edited March 19, 2016 by pavelcherepan

[StringJunky]

In a nutshell all is because now we have better diagnosis technologies and generally longer life expectancy giving more time for cancer to occur.

 

It takes a while in order for DNA replication errors to accumulate to start growth of malignant tumor and a bit of bad luck too, so if your life expectancy is low you probably won't live long enough for cancer to appear, although it still might happen.

 

Also keep in mind that majority of those cancers would be breast and prostate cancers which have efficient diagnosis methodologies (if not a bit unpleasant) and chances of survival are high.

 

https://en.wikipedia.org/wiki/Prostate_cancer

https://en.wikipedia.org/wiki/Breast_cancer

Yes, also, there were plenty more lethal diseases and physical problems to kill you in the past.

[Xalatan]

Aside from better diagnostic tools, screening for cancer will also introduce lead-time bias. Ie. a lot more cases of cancer will be picked up at an earlier asymptomatic stage, so it may seem more people are living with cancer.

[Strange]

Also, as fewer people die from other things that might have killed them in the past (malnutrition, heart disease, smallpox, minor infections, etc) they live longer and are more likely to get cancer.

[EdEarl]

Is there an environmental reason? In other words, are the chemicals created by industry and spilled into the environment causing an increase in cancer rates?

[John Cuthber]

Because evolution can't drive down the incidence of conditions -like cancer- that generally only affect you after you are old enough t have raised children.

"Is there an environmental reason? In other words, are the chemicals created by industry and spilled into the environment causing an increase in cancer rates?"

Generally, no.

we have cleaner air and water and less mouldy food than our forbears could have hoped for.

We also actually test synthetic chemicals to see if they are carcinogenic before we mass produce them.

So many or most carcinogens in the environment are natural- sunlight is a big one- or long standing ones like soot.

 

Occasionally we screw up on this- diesel smoke is possibly an example. The very fine particles produced by modern, fuel efficient, engines can penetrate deeply into the lungs and they might be more of a problem than larger particle sizes.

 

The other significant factor that has changed is that more of us are fat; and being fat increases the risk of cancer.

Do you include food among "chemicals created by industry and spilled into the environment"?

 

However the simple answer is that, if our modern environment was killing us to a greater extent than in the past, by any mechanism we would have shorter lifespans; we don't.

Edited March 19, 2016 by John Cuthber

[CharonY]

To summarize:

- the largest factor is that we grow older. Most cancer forms are correlated with age

- improved diagnostics allow detection at pre-symptomatic stages

- a very small proportion may be associated with lifestyle (tanning, obesity etc.) but are more than likely to be offset by decrease in smoking

[swansont]

Put in a slight different way than some previous posts: if you're looking at deaths, this is a zero-sum game. When you die, it has some cause. So if you reduce death from one cause, other cause(s) must increase in prevalence. But that's because of the way you are viewing the issue.

 

http://www.infoplease.com/ipa/A0005124.html

The people that used to die of (insert the malady of your choice) now survive or avoid it, but that just means they die of something else later on. In the US 50 years ago, more than 500 people per 100,000 died from heat disease. Now it's under 200. Cancer went up slightly over those years, but now it's even lower than it was back then. But since the overall death rate is lower, it represents a larger fraction of deaths. So it's only relatively more prevalent for this group. In absolute terms it isn't. Almost 1100 deaths per 100k 50 years ago vs just under 500 (for what's listed). But because cancer deaths have only dropped slightly in absolute, normalized terms, it was 18% of deaths back then and almost double that now

[Arete]

From an evolutionary perspective, cancer is a result of somatic mutations which disrupt cell signalling, cell division and/or apoptosis. As somatic mutations accumulate over the lifespan of an individual, the longer you live the higher the probability that a somatic mutation will occur that causes malignant cell growth.

 

In other words, it becomes a numbers game in game theory terms - the longer you "play", the higher the likelihood you'll "lose". As we've done a very good job of reducing mortality due to infectious disease, more individuals live long enough to get cancer.

Edited March 21, 2016 by Arete

[Xalatan]

The clonal evolution model of cancer is attractive and mainstream. I have also heard of an alternative hypothesis where somatic cells accumulate genetic lesions relatively early on in the human lifespan, for example via viral illness in childhood, only to be expressed as dysplasia when gate keeper mechanisms like immunity become suppressed later on in life due to the process of aging.

[nec209]

The clonal evolution model of cancer is attractive and mainstream. I have also heard of an alternative hypothesis where somatic cells accumulate genetic lesions relatively early on in the human lifespan, for example via viral illness in childhood, only to be expressed as dysplasia when gate keeper mechanisms like immunity become suppressed later on in life due to the process of aging.

 

Well some people say it could be the food we eat or that we live longer now and so people are getting cancer. Say in the past people would only live to their mid 30's and now people live to they are in their 70's and 80's and are getting cancer.

 

But it does not explain why some people in their 30's and 40's ge cancer.

Edited April 7, 2016 by nec209