WEDNESDAY, Feb. 15 (HealthDay News) -- A new blood-thinning medication called semuloparin reduces the risk of blood clots in people undergoing certain cancer treatments, new research shows.

When people with cancer are treated with chemotherapy, they have an increased risk of developing blood clots (venous thromboembolism). These clots can be dangerous, and have the potential to cause heart attacks or strokes.

This new drug reduced the risk of blood clots by 64 percent, according to the study, which was funded by Sanofi, the drug's manufacturer. Sanofi was also responsible for the analysis of the study's results.

Semuloparin, which is not currently approved by the U.S. Food and Drug Administration, didn't appear to increase the risk of excessive bleeding, which can be a side effect of blood thinners.

"Thromboembolism and the effects are very significant," said Dr. Stephanie Bernik, chief of surgical oncology at Lenox Hill Hospital in New York City. Even if blood clots don't cause life-threatening complications, they can cause lifelong problems, such as pain and a decreased ability to exercise, she explained.

"What's interesting about this paper is that they're decreasing the rate of thromboembolism without increasing bleeding. This needs to be confirmed in other studies, but this drug may play an important role for cancer patients in the future," said Bernik, who was not involved with the research.

The current study included more than 3,000 people from 47 countries. All had been diagnosed with cancer, including cancers of the lung, pancreas, stomach, colon, rectum, bladder or ovary.

The study volunteers were randomly assigned to one of two groups. One group received treatment with semuloparin, which is a type of heparin, while they were undergoing chemotherapy. The other group received a placebo.

The medication or the placebos were given as an injection once a day. Treatment lasted an average of 3.5 months.

Blood clots occurred in just 1.2 percent of those taking semuloparin compared to 3.4 percent of those on the placebo, according to the study.

The incidence of any type of excessive bleeding was 2.8 percent for the semuloparin group and 2.0 percent in those on placebo. Major bleeding occurred in 1.2 percent of those on semuloparin and 1.1 percent of those on placebo.

Results of the study are published in the Feb. 16 issue of the New England Journal of Medicine.

In addition to preventing clots, heparin medications may also help fight cancer tumors, according to the authors of an accompanying editorial in the same issue of the journal.

"This study by itself did not show any effect on mortality, but when we included it in a meta-analysis, we found that there is a likely survival benefit," said one of the editorial's authors, Dr. Elie Akl, an associate professor of medicine at the State University of New York at Buffalo.

The meta-analysis done by Akl and his co-author reviewed 11 studies including more than 6,000 people taking heparin medications during chemotherapy. They concluded that for every 1,000 people being treated with chemotherapy for cancer, there would be 30 fewer deaths if people were also treated with heparin during their chemotherapy. They also estimated that there would be 20 fewer blood clots. And, they estimated that there would be one more major bleeding episode and five more minor bleeding episodes if everyone on chemotherapy were to receive heparin treatment.

"Patients with cancer, who have a low risk of bleeding and who have no problem with injecting themselves with heparin, are likely to benefit in terms of survival from heparin treatment," he said.

What isn't yet clear, Akl said, is if heparin would provide more or less benefit depending on the type of cancer someone has, and how far advanced the cancer is. He said that there are currently six different studies under way to help answer those questions. The cost of the medication is also unclear, since it has not been approved for use in the United States yet.

More information

To learn more about blood clots and cancer, read this information from the American Society of Clinical Oncology.