Delaying the recurrence of cancer is good. Leading to other types of cancer is bad. What if a drug does both? News of that possibility gave Celgene's (Nasdaq: CELG) shares a 9% haircut earlier today.

A pair of trials showed that multiple myeloma patients treated with Revlimid lived longer than those taking placebo, but also had a higher incidence of secondary cancers.

Not exactly a good thing for a company whose strategy for increasing sales of Revlimid includes using the drug early in disease progression, and for a longer period of time.

But before we throw the drug out, let's put things in perspective. The increase could owe solely to chance. Remember, Merck's (NYSE: MRK) Vytorin looked like it was increasing the risk of getting cancer, but that seems to have been shrugged off. Revlimid is also keeping patients alive longer, which gives them more of a chance to get another type of cancer. The secondary tumors might have nothing to do with taking the drug.

We also have to keep the side effect in perspective. Yes, getting cancer is bad, but the alternative -- having the multiple myeloma come back -- is just as bad. Unlike GlaxoSmithKline's (NYSE: GSK) Avandia or Abbott Labs' (NYSE: ABT) Meridia, where side effects outweighed benefits of the drugs, the extended survival on Revlimid could more than offset a small increase in the incidence of secondary cancers, even if it turns out that increase is real.

Celgene could be a nice bad-news buy, just like it was in 2009. Sure, there's some reason to be worried, since most of Celgene's growth story is tied up in Revlimid; the drug made up 70% of revenue last quarter. But I wouldn't write off Revlimid just yet, either.

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Fool contributor Brian Orelli, Ph.D., doesn't own shares of any company mentioned in this article. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. GlaxoSmithKline is a Motley Fool Global Gains choice. The Fool owns shares of and has written covered calls on GlaxoSmithKline and has a disclosure policy.