If the annual American Society of Clinical Oncology medical conference is any indication, the battle over the competing drugs to treat numerous types of cancer is just heating up. On Monday, ImClone Systems (NASDAQ:IMCL) took another step to help solidify lead drug Erbitux as one of the top colorectal cancer therapies.

Erbitux has been approved to treat metastatic colorectal cancer after other treatments like chemotherapy have failed. It is also approved to treat head and neck cancer. ImClone is running multiple clinical trials to try to broaden the drug's use to earlier-stage colorectal cancer patients and other cancers.

Monday, ImClone announced that the Food and Drug Administration had accepted a supplemental Biologics License Application to try to improve the Erbitux marketing label so the company may market the drug as the "only biologic therapy to demonstrate overall survival" when used as a single agent in late-stage colorectal cancer.

The FDA granted ImClone a priority review on this labeling issue, and the FDA's decision on whether or not to approve Erbitux for this indication is expected in October.

Investors shouldn't discount the importance of an approved drug's product label. The sales of many a compound have been inhibited because of a restrictive label or onerous "black box" safety warnings on the label.  Getting the added monotherapy survival data on the Erbitux label isn't nearly the coup that is getting the drug approved to treat an earlier stage of the disease. At the very least, though, it should help Erbitux's sales versus its closest competitor, Amgen's (NASDAQ:AMGN) Vectibix. 

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Fool contributor Brian Lawler does not own shares of any company mentioned in this article. The Fool has a disclosure policy.