March 20, 2012— -- A daily aspirin may cut your risk of cancer, new research suggests. But doctors advise that there's no reason for everyone to start taking it -- at least not yet.
In three studies published in the Lancet and the Lancet Oncology on Tuesday, British researchers analyzed data from more than 50 studies and found that those who took daily aspirin for at least three years were less likely to develop cancer -- and if they did, it tended to be less advanced. Patients who took daily aspirin were 36 percent less likely to be diagnosed with metastatic cancer, or cancer that had already spread throughout their body.
Additionally, individuals taking aspirin for five years or more were 15 percent less likely to die from cancer. Previous research had only shown such benefits for patients taking aspirin for longer periods of time.
Nowhere was the evidence stronger than it was for colon cancer. Researchers found that patients who were diagnosed with localized colon cancer while taking daily aspirin halved the chance that their disease would spread.
Aspirin is a relatively inexpensive and easy-to-take medication that millions of Americans already use. The U.S. Preventative Services Task Force recommends men between the ages of 45 and 79 take aspirin daily to prevent heart disease, and they also recommend that women aged 55 to 79 take a daily aspirin to ward off stroke. The notion that this same medication may be able to prevent cancer is significant.
Dana Garmany of Scottsdale, Ariz., was not part of this study -- but he did have cancer. At the time of his diagnosis with advanced colon cancer, he said, his doctors advised him to keep taking the aspirin that he had been taking for about a year due to his family's history of heart disease. Today, 40 months after having the tumor removed and receiving chemotherapy, he remains disease-free.
Garmany said he did not know for sure whether it was the aspirin that prevented his cancer from spreading earlier. But he said taking the aspirin has been easy, and since it may have helped him in his cancer battle as well as his heart health, he added, "I feel like I'm getting two-for-one."
Cancer experts contacted by ABC News said they are excited about what these findings might mean for future research and treatment.
"This is very encouraging information," says Dr. Roy Herbst, Chief of Medical Oncology for the Yale Cancer Center in New Haven, Conn. "It suggests that aspirin could play a very important role in cancer prevention."
"I am intrigued by the consistency of the findings and this is something that can be implemented quickly that people are not opposed to," said Dr. Kristen Moysich, professor of oncology at the Roswell Park Cancer Institute in Buffalo, N.Y. "It is an easy thing to do."
But precisely how patients like Garmany and others might benefit from aspirin has yet to be fully understood, doctors say.
"No one knows exactly what the mechanism is of how aspirin helps prevent cancer," said Asad Umar, chief of the Gastrointestinal and Other Cancers Research Group of the National Cancer Institute.
Umar said aspirin's anti-inflammatory action might have something to do with the benefits that researchers have seen. Others, like Jay Whelan, suggest aspirin may interfere with the processes in the body that cause tumors to grow.
"Aspirin also probably works in ways that we don't quite understand," said Whelan, who heads the Department of Cellular and Molecular Nutrition at the University of Tennessee, Knoxville. "We don't know the mechanism, and it is very difficult to make a blanket public health statement without knowing the mechanism.
"While this backs everything up, I think people should consult their physicians."
The research may not be the last word on aspirin and cancer. Previous studies -- including the large Women's Health Study and the Physicians' Health Study -- have suggested no link between aspirin consumption and reductions in cancer occurrence or cancer-related death. The researchers behind the current study wrote that they excluded these major pieces of research because patients in these studies did not take aspirin on a daily basis.
Even then, the conclusions of the new research do not support a specific dose of aspirin -- so even if there is an effect, those who hope to benefit from it may find themselves at a loss over how much to take.
And although aspirin is a commonly used medicine available over the counter, it is not necessarily safe. People taking aspirin have an increased risk of bleeding, including bleeding in the gastrointestinal tract. This can be very dangerous, and the risk of it happening increases with higher doses.
Most agreed that before medical experts can make any concrete recommendations, further study is needed.
"Because these results are new, it will take time for the broader scientific community to evaluate the data in the context of existing knowledge and to consider whether the clinical guidelines should be changed." said Eric Jacobs, strategic director of Pharmaco-Epidemiology at the American Cancer Society, Inc.
"It is important for patients to follow colon cancer guidelines already in place and get their recommended colon cancer screening tests."
ABC News' Lisa Stark contributed to this report.