Along with its other benefits, an aspirin a day may help keep head and neck cancers away, a new long-term study suggests. It wasn't so much the amount of aspirin that was taken but the length of time that people were on the drug that mattered, said study co-author Mary E. Reid, an assistant professor of oncology at Roswell Park Cancer Institute, in Buffalo, N.Y.
"We found that duration really seemed to make a difference," Reid said. "It was more duration than frequency. Taking aspirin for under 10 years did not have a significant effect, [but] taking it 10 years or more was associated with a 30 percent reduction in cancer."
The protective effect was not seen in heavy smokers and drinkers, however. Her team reported the findings in the November issue of the Archives of Otolaryngology.
According to the U.S. National Cancer Institute, head and neck cancers comprise about 2 percent to 5 percent of all malignancies in the United States, with about 39,000 new cases diagnosed each year. Experts estimate that about 85 percent of these cancers are linked to tobacco use.
Reid and her colleagues' study included patients treated at Roswell Park -- 529 with head and neck cancer, another 529 without the malignancy. Participants were matched for age, sex and smoking status. They were also asked about their use of aspirin over the preceding decades.
"A consistently decreasing trend in risk was noted with increasing duration of aspirin use," the researchers reported. "Risk reduction was observed across all five primary tumor sites, with cancers of the oral cavity and oropharynx [upper throat] exhibiting greater risk reduction."
Earlier studies have linked aspirin use to reduced risk of other forms of cancer, such as prevention studies of colorectal cancer that Reid herself has worked on.
But it's still too early to recommend routine use of aspirin as a cancer-preventive measure, said Dr. Michael Thun, vice president for epidemiology and prevalence research at the American Cancer Society.
The new retrospective study "does not have the strongest kind of design" because participants were asked about aspirin use after they were diagnosed with cancer, Thun noted. Still, he said, "the results were internally quite consistent, with a lower risk the longer they used aspirin."
The idea that aspirin and other non-steroidal anti-inflammatory drugs ( NSAIDs) can help prevent cancer is "quite plausible, but the evidence is limited," Thun added. However, the theory is plausible enough for the U.S. National Cancer Institute to be sponsoring a large-scale study using Celebrex, also a member of the NSAID family. Results are expected in about two years, Thun said.
Aspirin's cancer-fighting effect appears to be linked to the molecular mechanism by which NSAIDs fight pain, both Reid and Thun said. The medications inhibit an enzyme called cox-2, whose activity is known to increase in pre-malignant lesions. Inhibiting the enzyme may also help slow the proliferation of cells, Reid said.
Anyone who wants to take aspirin as a cancer preventive should first consult their physician, Reid cautioned. "You should always talk to a physician before taking anything chronically," she said.
Taking aspirin each day does have its risks, Thun said. "At this point, aspirin is still not recommended for prevention of any cancer because of the risks of bleeding, particularly gastrointestinal," he said. "What is still missing is proof that the benefits of taking aspirin outweigh the risks."