HOUSTON-- Many cancer patients who have heart attacks often are not treated with life-saving aspirin given the belief in the medical community that they could experience lethal bleeding.

Researchers at The University of Texas M. D. Anderson Cancer Center, however, say that notion is now proven wrong and that without aspirin, the majority of these patients will die.

Researchers say that their study, to be published in the Feb. 1, 2007, issue of the journal Cancer and now available online, turns common medical assumptions upside down.

Because aspirin can thin blood and cancer patients experience low platelet counts and abnormal clotting, physicians view aspirin as a relative contraindication. Given that blood platelets are responsible for the clotting process, physicians do not eagerly prescribe aspirin as a standard treatment.

In this study, however, the investigators found that nine of 10 cancer patients with thrombocytopenia (low platelet count) who were experiencing a heart attack and who did not receive aspirin died, whereas only one patient died in a group of 17 similar cancer patients who received aspirin. They also found aspirin helps cancer patients with normal platelet count survive heart attacks, just as it does for people without cancer.

According to the World Health Organization there are approximately 10 million cancer patients worldwide, of which 1.5 million may develop blood clots during their cancer treatment and, as such, are at a much higher risk of dying from heart disease if not treated properly.

No guidelines currently exist for treatment of heart attacks in patients with cancer. Physicians are especially perplexed about what to do for cancer patients with thrombosis (blood clots), a condition that affects about 15 percent of all cancer patients and can be due to the use of chemotherapy or the presence of cancer.

The study found that heart attack patients with low platelets who did not receive aspirin had a seven-day survival rate of 6 percent, compared with 90 percent survival in those who received aspirin. There were no severe bleeding complications in patients who used aspirin. Conversely, patients with low platelet counts who formed a blood clot and were not exposed to aspirin died.

The beneficial effect of aspirin also was seen in patients with normal platelet counts. Seven-day survival was 88 percent in aspirin-treated patients as compared to 45 percent in patients who did not receive aspirin, the researchers found.

There were parallel findings for those patients in either group who were treated with beta-blockers, which block the heart's use of adrenalin. The protective effect was not as strong as seen with aspirin, but was still life-saving.

In those patients with a normal platelet count, 91 percent survived seven days when treated with beta-blockers, whereas 36 percent survived if they were not treated with the agent. In the thrombocytopenic group, 73 percent survived seven days when treated with beta-blockers, whereas only 13 percent survived if they were not treated.