CTV.ca News Staff–February 16, 2010–Breast cancer survivors who regularly take acetylsalicylic acid may be less likely to see their cancer return, a new study suggests.

The study of more than 4,000 nurses with breast cancer, published Tuesday in the Journal of Clinical Oncology, showed that those who took ASA — most often to prevent heart disease — had a 50 per cent lower risk of dying from breast cancer and a 50 per cent lower risk that the cancer would return or spread.

ASA — more commonly known in Canada by the brand name Aspirin — is a medication used to relieve minor aches and pains and as an anti-inflammatory.

Previous studies have looked at the connection between non-steroidal inflammatory drugs (or NSAIDs), including ASA, and breast cancer. But according to one of the study’s authors, this is the first to look at ASA in particular.

“To my knowledge, it’s the first study to specifically show aspirin intake is associated with a lower risk of dying among women who have had breast cancer,” said Dr. Michelle Holmes.

Because the study was observational, and not a controlled experiment, more research is necessary to prove a direct link between regular ASA intake and increased chances of survival for breast cancer survivors.

“This is an observational study, so we can’t prove Aspirin causes improved survival,” Holmes said.

Holmes and her colleagues studied responses from 4,164 female registered nurses who participated in the U.S. Nurses’ Health Study and were diagnosed with breast cancer between 1976 and 2002. The nurses were observed until June 2006. Over that time, 341 of the nurses died of breast cancer.

The nurses were asked to report their ASA use in questionnaires sent by the researchers every two years from 1976 to 2006.

The study found that those who took two to five ASA tablets a week to prevent heart attack and stroke lowered the risk their cancer would return or spread by 60 per cent. Taking two to five ASA tablets a week was also associated with a 71 per cent reduction in the risk of dying of breast cancer.

Dr. Mark Clemons, a medical oncologist with the Ottawa Hospital, said the study’s findings are “possibly intriguing” but need to be considered with previous evidence.

Some retrospective studies “show Aspirin may reduce breast cancer … many others show that it doesn’t seem to,” Clemons told CTV’s Avis Favaro.

Clemons said there could be other factors at play besides ASA that might have affected survival rates, including the idea that women who regularly take ASA may be more diligent about taking their breast cancer medications than those who don’t.

“We know in the treatment of breast cancer, only 60 per cent will take their medication long-term, as directed by their oncologist,” he said.

“Given that the majority of studies looking at the role of aspirin have not shown a positive breast cancer effect, one must be concerned there is more to the story than meets the eye… and we will only get the answer from large randomized studies.”

Previous studies have explored the link between ASA and the risk of breast cancer, although researchers agree more work is necessary before the links between the common medication and breast cancer prevention can be proven beyond a doubt.

With a report from CTV’s Avis Favaro and producer Elizabeth St. Philip