Fun Science Fact: Cancer is Random

By Edward Ashton
Feb 23, 2019 · 769 words · 3 minutes


From the author: A post containing actual science rather than the fictional kind.


When we hear that someone has been diagnosed with cancer, the first thing that comes into most of our minds is this: why? I don’t think it matters if the person in question is a friend, or a family member, or a celebrity, or a random stranger. Was he a smoker? Did she spend too much time in tanning beds? Did he fail to follow a strict vegan diet, or not drink enough fresh juice, or cook with teflon, or forget to take his vitamin D? Sympathy and empathy kick in later, but our first psychological impulse is to protect ourselves--because if we can identify the thing that this person did wrong, especially if it’s something we think we’re doing right, then we can tell ourselves that it will never happen to us.

Here’s the thing, though:  when it comes to cancer, there is no why. Cancer is random.

To understand why this is, we need to understand what really causes cancer. Cancerous cells are essentially normal human cells--breast or liver or brain or bone--in all ways but two: they learn how to evade the immune system, and they forget how to die.

The proximate cause of these changes is a series of genetic mutations. A typical malignant cell has between five and ten distinct genetic errors, each of which is essentially unrelated to the others. Errors in a cell’s genetic code crop up on a fairly regular basis during cell division and reproduction. During this process, the cell’s DNA gets split down the middle, and then reconstructed into what are supposed to be two exact copies of itself--one for each daughter cell. Sometimes, however, the reconstruction includes errors. A C goes in where a G should have gone, and a mutation is introduced. Most of the time, these errors are harmless.  Other times, they’re immediately fatal to the daughter cell. Sometimes, though, if they occur in just the right place, they can wind up changing the cell’s functions in a way that contributes to the development of a malignancy.

The important thing to understand about this process is that it is essentially random.  Every time one of your cells divides, you’re rolling the dice. The probability that you will develop the right set of mutations to produce a malignancy is therefore related primarily to the rate at which cells divide, and the probability that one of those divisions will include a mutation. That’s why you see tumors develop most frequently in tissue types that divide rapidly, like breast, lung, and colon, and less frequently in tissues that divide slowly, like bone and brain.

This is not to say, of course, that nothing you do or don’t do affects the chances that you’ll develop cancer. Anything that causes cells to divide more rapidly gives you more throws of the dice. That’s why chronic inflammation is associated with a higher rate of tumor development. You can also weight the dice to a certain extent. Cells that divide in the presence of ionizing radiation (x-rays, for example) are more likely to have transcription errors. The same is true for cells that divide in the presence of certain organic solvents and other noxious chemicals. Still, none of those things actually cause cancer. They just shift the odds a bit.

Here, on the other hand, is a partial list of things that do not affect the odds that a particular cell division will result in a malignant transcription error:

  • kale
  • yoga
  • positive thinking
  • karma
  • refined sugar
  • the power of prayer
  • juice cleanses
  • one weird trick, as seen on the internet

Cancer is not the result of a moral failure. It is not caused by the evils of modern society. It is not something that you can make yourself safe against. Cancer has been with us for as long as we have been human, and probably for as long as we have been multi-cellular. It will almost certainly be with us in one form or another for as long as we persist.

So then, what can we do? Well, try this for starters: the next time you hear about someone who’s been diagnosed with cancer, don’t spend any time or energy trying to figure out what exactly he did to bring it on, and for the love of God don’t give him any suggestions about what he could have done to prevent it.  Instead, try to focus on the fact that he’s got a hard road ahead of him. Spend that time trying to think of what you can do to help.