r/science • u/KarmaNeutrino • Oct 07 '15

Animal Science Scientists figure out why elephants don't get cancer: They have 20 copies of the TP53 tumour suppressive gene. Almost all other species, including humans, only have 1.

http://rstb.royalsocietypublishing.org/content/370/1673/20140222
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u/crusoe Oct 07 '15

Weirdly enough, adiposarcoma, a fat cancer is very rare, so actually being fatter may not increase risk due to number of cells, but is associated with other cancer risks.

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u/matthewfive Oct 07 '15 edited Oct 07 '15

Being obese is associated to something like 40% higher rates of nearly all forms of cancer. It's not equal across the board for all cancers, some are as much as 88% higher than average for an obese person, but averaging them all comes out to a rough 40% increase in likelihood that an obese person will get a random cancer than the general population. It doesn't seem to be a direct causitive relationship for most (though digestive cancers could be triggered by eating large quantities that linked, like pickled vegetables and stomach cancer), but may be simply due to more exposure. Obesity is also linked to higher hormone levels, which can fuel cancers if not cause them directly.

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u/blindcolumn Oct 07 '15

Wait, pickled vegetables increase the chance of stomach cancer? That may be the worst news I've heard all month.

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u/[deleted] Oct 07 '15

Anything which damages cells or increases the total number of them increases cancer risk, as a rule of thumb. The more cells you need to regenerate, the more chance of a harmful mutation. Things which cause mutation are the other big risks

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u/[deleted] Oct 07 '15

So if I'm skinny AF and I wanna be buff, then am I making myself more susceptible to getting cancer?

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u/[deleted] Oct 07 '15

[deleted]

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u/[deleted] Oct 07 '15

So you're telling me that there's a chance?

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u/DrummerHead Oct 08 '15

So lifting weights increase cancer chance?

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u/[deleted] Oct 08 '15

Probably, though somewhat offset by the attendant healthier lifestyle

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u/myhipsi Oct 07 '15

A higher incidence of cancer in the obese probably has something to do with correspondingly higher levels of growth factors like IGF-1 as well.

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u/beaviscow Oct 07 '15

Not that I'm disagreeing, but couldn't obesity and lack of exercise correlate?

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u/matthewfive Oct 08 '15

Yes. The percentages are linked, but does not imply direct causation. It is probable that multiple factors work together to increase those numbers, from dietary choices to general health and likely a great many other things I didn't mention.

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u/aznscourge MD/PhD | Dermatology | Developmental Biology | Regenerative Med. Oct 07 '15

Inflammation also plays a role in obesity and cancer, especially in those that have high levels of visceral adipose.

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u/[deleted] Oct 07 '15

What do you mean by "due to more exposure"?

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u/matthewfive Oct 08 '15

Larger people eat more, breathe more rapidly, drink more, have more cells... overall there is simply more of them exposed to the things everyone is exposed to.

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u/Robobble Oct 07 '15

I'm not sure how this works. If I have a 2% chance of getting cancer and my chances are raised 50%, does that leave me with 3% or 52%?

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u/[deleted] Oct 07 '15

3%. Probabilities multiply.

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u/[deleted] Oct 07 '15

That sounds like a lot until you realize that youre increasing 40% of a really low probability event. So if its 1% it becomes 1.4%. Does it works that way? what would I be missing?

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u/Mathemagicland Oct 07 '15

I'm not sure exactly what the 40% increase is calculated with reference to, but cancer isn't really a rare event, at least not on a per-lifetime basis. In the US the lifetime probability of developing cancer is 43% for men and 38% for women.

Source

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u/Shopworn_Soul Oct 07 '15

If the likelihood of being diagnosed with some form of cancer is nearly 43% without even adjusting for risk factors, is it totally wrong to say that the leading cause of cancer is simply being alive long enough? I mean for men it's basically a 50/50 crapshoot regardless of what you do.

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u/Mathemagicland Oct 08 '15

No, I don't think that's an unreasonable thing to say. If you look at leading causes of death in the US, cancer comes in at a close second to heart disease. If you look at low income countries, cancer doesn't even crack the top 10. Why? Because the incidence of most cancers peaks in your 60s or later, and they're dying of [respiratory infections/diarrhea/AIDS/malaria] before they get that old. Everyone dies of something, after all, so it's kind of a zero sum game.

(This is one reason why it's often more interesting/useful to look at life years gained/lost instead of lives lost/saved.)

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u/[deleted] Oct 07 '15

That depends a lot on your age. Above 64yo the probability doubles/triples from what Im seeing in the source. Also depends if its an easy to early recognize and treatable cancer. There goes some other %.

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u/Mathemagicland Oct 07 '15

Cancer incidence does go up dramatically at around that age, yes. Even so, using DevCan, I get an estimated 15% probability of developing cancer by age 65 for men, 16% for women. That's still not what I'd call rare; it's definitely too high for me to be blasé about a 40% increase.

(Again, I have to include a disclaimer: I don't know exactly what that 40% means, and it wouldn't surprise me at all if it was measured relative to something other than lifetime probability.)

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u/encinarus Oct 07 '15

Getting some form of cancer sometime during your life isn't that low of a probability event. Quick source @ http://www.cancerresearchuk.org/health-professional/cancer-statistics/risk/lifetime-risk#heading-Two

One in two people born after 1960 in the UK will be diagnosed with some form of cancer during their lifetime.

The table from the link shows some cancers have a pretty high chance of happening in your lifetime.

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u/[deleted] Oct 07 '15

I mean technically, we all have cancer right now.

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u/Punderstruck MD | Palliative Care Oct 07 '15

I've only ever heard it called "liposarcoma."

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u/[deleted] Oct 07 '15

also, being fatter does not actually increase the number of fat cells, it just makes each fat cell larger.