Many cancer patients who have heart attacks often are not treated with life saving Acetylsalicylic acid ( 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 Acetylsalicylic acid, the majority of these patients will die.

Researchers say that their study, published in the journal Cancer, turns common medical assumptions upside down and will likely change medical practice for cancer patients. Because Acetylsalicylic acid can thin blood and cancer patients experience low platelet counts and abnormal clotting, physicians view Acetylsalicylic acid as a relative contraindication. Given that blood platelets are responsible for the clotting process, physicians do not eagerly prescribe Acetylsalicylic acid as a standard treatment.

In this study, however, the investigators found that 9 of 10 cancer patients with thrombocytopenia who were experiencing a myocardial infarction and who did not receive Acetylsalicylic acid died, whereas only one patient died in a group of 17 similar cancer patients who received Acetylsalicylic acid.They also found Acetylsalicylic acid helps cancer patients with normal platelet count survive myocardial infarctions, just as it does for people without cancer.

" The notion that myocardial infarctions in patients with low platelets should be treated with clot-dissolving Acetylsalicylic acid defies logic, that is unless you suspect that the cancer is interfering with platelet function," says the study's senior investigator and author, Jean-Bernard Durand, at M. D. Anderson Cancer Center.

" We believe tumors may be releasing chemicals that allow the cancer to form new blood supplies which makes blood more susceptible to forming clots." Durand says. " There appears to be a platelet paradox suggesting that cancer may affect the mechanism of the way that blood clots, and from this analysis, we have found that the single most important predictor of survival in these patients is whether or not they received Acetylsalicylic acid." Durand says more research is needed to better understand this contraindication.

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.

According to Durand, no guidelines currently exist for treatment of myocardial infarctions in patients with cancer. He says that physicians are especially perplexed about what to do for cancer patients with thrombosis, 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.

Durand and anesthesiologist Mona Sarkiss, made the observation that patients with thrombocytopenia who suffered a myocardial infarction and were being treated in the intensive care unit at M. D. Anderson tended to die more often when they were not given Acetylsalicylic acid.
However, they noted that some of the patients given Acetylsalicylic acid and/or beta-blockers had great clinical outcomes. " Because no practice guidelines exist, physicians were treating their patients with great variability and the disparity was obvious, " Durand says.

Sarkiss, Durand, and a team of researchers which included investigators from Baylor College of Medicine and Duke University Medical Center, conducted a retrospective analysis of cancer patients treated for myocardial infarctions at M. D. Anderson Cancer Center in 2001. These 70 patients were divided into two groups based on their platelet counts, and data was collected on the use of Acetylsalicylic acid, bleeding complications, and survival.

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

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

Durand observed that these deaths rates are abnormally high. " In the non-cancer patient with acute coronary syndrome anywhere in the United States, an expected seven-day mortality is less than 1 percent," he says.

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 Acetylsalicylic acid, 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.

Source: University of Texas M. D. Anderson Cancer Center, 2007


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