Friday, January 9, 2015

More on Luck and Cause

Earlier this week, I posted a blog criticizing the conclusions reached in a highly publicized paper written by a group of scientists at Johns Hopkins Medical Center. The authors conclude that "bad luck", rather than environmental or genetic causes, is responsible for the bulk of human cancers. My prior blog post explained why Hopkins is wrong.

After the blog was written, I received some very interesting feedback from a LinkedIn group (Science writers), much of which centered on the different ways that people use the words "luck" and "cause". Though mathematicians will despair, the word "good luck" is routinely applied to just about anything that has desirable outcome. So if a high school student gets a perfect score on the SAT exam, he or she was very very lucky. If you would interject to say that luck had nothing to do with it ("It was all due to student's high intelligence!"), you would be informed that the intelligence was a matter of luck, being as the student had done nothing to earn his or her intelligence. If you were to suggest that the "cause" of the high score was hard work, you would be told that "hard work" was just one of many conditions that led to the high score (e.g., "lucky" intelligence, a good night's sleep the night before, growing up in a stable living environment where current events, history and literature are discussed). There being many different "causes," it wouldn't make much sense to think in terms of any specific cause, and you might as well chalk it up to just plain good luck.

Getting back to biology and disease, consider these hypotheticals:

If you have 5 people living with an Ebola patient, and three of the five come down with the disease, would you say that these three came down with Ebola because they were "unlucky"? Or would you say that these three came down with Ebola because they were infected with the virus [and the other two were not]?

Would you say that the Ebola virus caused the infection in these three individuals? Or would you say that many factors, such as "luck", the environment, low innate viral resistance, poor nutrition, all set the stage for their infections, and that the Ebola virus was just one of many ingredients in the brew?

There's a real danger with using "luck" to describe events that we do not understand or cannot predict. Likewise, causation can be deceptive when dealing with a multi-step process that plays out over years or decades (like cancer).

When I think about "cause" I'm usually applying the "but-for" criteria ("but-for" this, that would not have happened). So, for me, Ebola virus causes Ebola hemorrhagic fever, and infections are not a matter of luck. Likewise, for me, there are "but-for" causes of cancer (e.g., chemicals, viruses, predisposing genes), and many important modifying factors that probably don't rise to the level of "but-for" causes (e.g., cell proliferation, DNA repair, genomic and epigenomic influences, regression-causing events, immune status); and cancer is not caused by bad luck.

Today, cancer has become the quintessential "bad luck" disease. In a prior blog, I described examples of "bad luck" cancers that transformed into "specific cause" cancers, when we studied the data. My personal opinion is that most cases of cancer are associated with known "but-for" causes. As we learn more and more about the different types of cancers, particularly the huge variety of rare cancers, we continue to find specific causes for specific cancers. I just assume, perhaps incorrectly, that every cancer has a cause.

I urge everyone reading this blog to also read my prior blog, which provides a full rebuttal to the Johns Hopkins "bad luck" cancer hypothesis.

- Jules Berman

tags: johns hopkins, press release, cancer news, bad luck, data repurposing, opinion, criticism, carcinogenesis, rare cancer, rare diseases, cancer incidence, comparative carcinogenesis, Jules J. Berman, Ph.D., M.D., cancer research, new findings, mutation rate, rebuttal, stem cell renewal, probabilistic models, data modeling, randomness, chance, misfortune, accident, unpredictable, causation, causative role, but-for, but for, sine qua non