Monday, February 09, 2009

Reefer Madness or Real Science?

Just saw an article via Yahoo! News linking marijuana use with testicular cancer. Long-time readers know that I have an interest in cancer and cancer research, and testicular cancer in particular, as my dad had it (the first of several cancers in his life).

I have to admit that any correlation between pot smoking and testicular cancer seems a bit odd to my non-medically-trained self (though my degree in Environmental Science is not entirely inapplicable here). What's really interesting to me here is looking at how the study is reported from several different wire services and other sources.

Here's the lede from the HealthDay News story I initially saw:
Smoking marijuana over an extended period of time appears to greatly boost a young man's risk for developing a particularly aggressive form of testicular cancer, a new study reveals.
That sounds pretty definitive, doesn't it? They do include some cautions from study authors later on:

Though Daling emphasized that the findings are preliminary, she suggested that attention should be paid.

"We know very little about the long-term health consequences of marijuana smoking," she cautioned. "So, although this is the first time this association has been studied and found -- and the finding does need to be replicated before we are really sure what's going on -- this does give some evidence that testicular cancer may be one result from the frequent use of marijuana. And that is something that young people should keep in mind."

And this:
"But certainly, the idea that cannabis may cause cancer cells to proliferate is interesting," Schwartz acknowledged. "It could, however, also be that recreational drug use is simply a marker for affluence, since we know that testicular cancer is traditionally a disease that is more common among the affluent. Or it could be a marker for some other event that comes along with it, that triggers lesions that lead to tumors. So, at this point, it's just not clear to me how exactly the association between marijuana and testicular cancer would work."
Now, the AFP story is much shorter, and carries this lede:
Smoking marijuana may increase the risk of testicular cancer by as much as 70 percent, a study published on Monday suggested.
Although they do quote Dr. Schwartz, there is no indication of the preliminary nature of the findings, or any suggestion that there might be other factors involved:
"Our study is not the first to suggest that some aspect of a man's lifestyle or environment is a risk factor for testicular cancer, but it is the first that has looked at marijuana use," said Stephen Schwartz, an epidemiologist and one of the report's principle authors.
Now, here's the Reuters lede:
Marijuana use may increase the risk of developing testicular cancer, in particular a more aggressive form of the disease, according to a U.S. study published on Monday.
And their quote from Schwartz is much more circumspect:
"This is the first study to look at this question, and by itself is not definitive. And there's a lot more research that would have to be done in order to be more confident that marijuana use really is important in a man's risk of developing testicular cancer," Schwartz said in a telephone interview.
CNN has the most balanced lede, and actually interviews scientists other than the study authors:
Do men who frequently smoke pot have a higher risk of testicular cancer than those who do not? It's possible, according to a new study. However, the researchers say the link is currently a "hypothesis" that needs further testing.
UPI (touting their "100 years of journalistic excellence") has a much briefer and less detailed story that starts with this:
Being a marijuana smoker at the time of diagnosis was associated with a 70 percent increased risk of testicular cancer, U.S. researchers said.
Perhaps more disturbing is the article title on that one: "Pot increases testicular cancer risk".

A blog at Scientific American starts with this:
Fellas, you might want to think, well, twice about following Olympic swimmer Michael Phelps' lead. A study published today in the journal Cancer linked frequent marijuana use to the possibility of a slim increased risk of testicular cancer.
The rest of the post is less folksy and more balanced and analytical, including these disclaimers:
The prevailing belief has been that a man's chances of developing testicular cancer is largely determined in the womb, as cells in the fetus are developing and those known as germ cells (which later develop into sperm cells) fail to mature properly. This work shows the possibility that marijuana use–an environmental factor–might also play a role. But researchers acknowledge that it does not prove a definitive link–and that there were weaknesses to the study, including that it was based on a relatively small group of men and relied on self-reported drug use, which can be iffy.
"We're not exactly sure what role the marijuana is playing," Daling says, but it has come out as a possible factor that warrants further investigation.

Len Lichtenfeld, deputy chief medical officer for the American Cancer Society, says that the study is a potentially promising clue, but that is by no means a firm conclusion.
Long story short: it makes a big difference where you get your health and science information. My take is that journalists are rarely trained in science at all, and tend to jump to whatever conclusion a study suggests, without necessarily reporting the scientific nuances and disclaimers (which I'm guessing they don't understand, or at least don't understand the importance of).

Probably most annoying to me is that none of the stories contained any links to the study itself or any way to get more information about it, other than either other new reports of the same study (which is how I started down this path today) or to past reports on related topics. A few mentioned that the study was published (some said "online") in the journal Cancer, but none indicated how to find that.

And for comparison purposes, here's the original press release from the Fred Hutchinson Cancer Research Center. It, too, says the study is published online, but doesn't say how to get there.

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