Bristol-Myers Squibb (NYSE: BMY) is up a lot today on an upgrade and some positive data coming out of the American Society of Clinical Oncology (ASCO) meeting this weekend, but investors need to be careful. Very careful.

Let's ignore the analyst's upgrade for now. It appears to be based somewhat on the data from ASCO anyway, and besides, analysts say the darndest things.

Of Bristol's two major presentations at ASCO, one seems fairly straightforward. Sprycel, which is currently used as a second line treatment for chronic myeloid leukemia (CML), beat the first-line treatment, Novartis' (NYSE: NVS) Gleevec. A first-line indication, if the FDA approves, should increase sales as some patients are cured or die and never make it to a second round of treatment.

But -- I said we needed to be careful -- Novartis' newer CML drug, Tasigna, also beat Gleevec, so it's likely that Sprycel will have competition if it's approved as a first-line therapy. We won't really know which one is better until Tasigna goes head to head with Sprycel.

Bristol's other major announcement from ASCO was for its drug, ipilimumab, for the treatment of metastatic melanoma. The drug extended survival 3.6 months longer than using just a gp100 peptide vaccine. The use of that kind of vaccine is to help stimulate the immune system of the patient against the cancer. What's confusing is that ipilimumab increased survival over just the vaccine by pretty much the same amount both when it was added to the vaccine and when it was used by itself. Does that mean the gp100 therapy isn't needed?

There aren't many treatment options for melanoma patients, which should work in Bristol's favor when the FDA decides ipilimumab's fate. But as InterMune (Nasdaq: ITMN) and Dendreon (Nasdaq: DNDN) -- the first time around -- have shown, a desperate need for treatment isn't sufficient by itself to get past the FDA.

Bristol-Myers Squibb has a lot going for it: a fat dividend of more than 5%, a decent pipeline, and a huge war chest that can be deployed to help it get through its patent cliff. I'm just not sure the drugmaker is worth 7% more today than it was on Friday. Investors need to be careful translating ASCO data into increased revenue and income; there's still plenty of uncertainly around the future of Sprycel and ipilimumab.

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