Another study has come out suggesting that certain cancer drugs may cause more trouble than they are worth - much more trouble.

The study, published in the Journal of the American Medical Association this month, found patients using drugs that are considered erythropoiesis-stimulating agents, or ESAs, increase their risk of death by 10%. They also increase by 57% the risk of developing deep vein thrombosis, or blood clots in the leg and lungs, the study said.

Wall Street took the news as seriously as the issue sounds. Shares of Amgen and Johnson & Johnson, who are the largest suppliers of the drugs in question, were slammed in mid-week trading after the study held the companies out as poster children for anti-anemia drugs that increase the risk of blood clots and death in cancer patients.

Amgen's Aranesp and Epogen and Johnson & Johnson's Procrit are ESAs. They're typically used with chemotherapy to ward off blood-cell reduction associated with chemo.

Amgen's stock price dropped 2% in afternoon trading, while Johnson & Johnson dipped about 1%.

Dr. Charles Bennett of the Northwestern University Feinberg School of Medicine in Chicago led the study, which compiled and examined data from 51 prior studies in more than 13,000 patients.

According to a report on CNN Money this week, this is not the first time problems have arisen for the ESA class. Bret Holley, a drug analyst for Oppenheimer & Co., dismissed the JAMA report as "old news," despite its apparent impact on company stocks.

"In 2007, the increasingly-cautious Food and Drug Administration toughened warning labels for ESAs to reflect the potentially fatal side effects of taking them in high doses," reports CNN. "These drugs are a major part of Amgen's franchise, and the ongoing safety concerns are largely responsible for the biotech's stock losing one-third of its value in 2007."

In a statement emailed to CNNMoney.com, Amgen said the study "does not define any new risks associated with ESAs, and the risk of [deep vein thrombosis] is included in current labeling and has been for some time. It's important that physicians and patients fully understand the benefit (transfusion avoidance) and risks and that these drugs be used appropriately according to the FDA approved labeling."

Johnson & Johnson also said that its drug is safe. Its subsidiary, Ortho Biotech, which makes Procrit, accused the study of being inaccurate.

"The company reaffirms that, when used according to product labeling, ESAs remain safe and effective and are the only proven treatment alternative to blood transfusions for patients with [chemotherapy-induced anemia,]" Ortho told CNNMoney.com.

All well and good, but when you're on the defensive and the issue is deaths related to drugs you produce, image really is everything.