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TUESDAY, June 19 (HealthDay News) -- Adding to already-conflicting data about sun exposure, vitamin D levels and cancer risk, new Australian research suggests that experiencing high levels of ultraviolet light and having sun-sensitive skin and a history of skin cancer each measurably lower the risk for developing deadly pancreatic cancer.
But U.S. cancer experts cautioned against making any lifestyle changes -- including tanning or altering vitamin D intake -- in response to the study, which is preliminary and does not prove these factors can prevent pancreatic cancer.
Comparing about 700 patients with pancreatic cancer from Queensland, Australia, to a roughly equal number of people from the general population, scientists led by Rachel Neale from the Queensland Institute of Medical Research found that participants born in areas with the highest levels of ultraviolet radiation had a 24 percent lower risk for pancreatic cancer than those born in areas of low UV radiation.
Those classified as having the most sun-sensitive skin had a 49 percent decreased risk of the malignancy compared to those with the least sun-sensitive skin, while participants with a history of skin cancer or other sun-related skin lesions had a 40 percent lower risk of pancreatic cancer than those with no reported skin lesions.
Dr. James D'Olimpio, director of palliative medicine/cancer pain and supportive oncology at Monter Cancer Center in Lake Success, N.Y., questions the findings. "This study is very innovative and I applaud the design, but translating it to what's really going on in pancreatic cancer is a stretch," he said. "The whole idea of UV exposure conferring protection . . . is counterintuitive. I looked at this study with interest but a high degree of skepticism."
The research is scheduled to be presented Tuesday at an American Association for Cancer Research conference at Lake Tahoe, Nev.
About 44,000 new cases of pancreatic cancer will be diagnosed in the United States this year, according to the U.S. National Cancer Institute, with more than 37,000 deaths expected. Originating in the pancreas, near many other gastrointestinal organs, the malignancy is often discovered after it has spread and is extremely difficult to control or cure.
The Australian researchers matched study participants by age and sex to others in the general population over four years, interviewing them about social, demographic and medical information along with details of their birth location, skin-cancer history and skin type. They categorized skin type by skin color, tanning ability and propensity to sunburn.
Study authors noted that contradictory data exist on so-called circulating vitamin D -- the amount of the vitamin present in the bloodstream as a result of sun exposure, not food or supplementation -- and its association with cancer risk.
D'Olimpio, who specializes in pancreatic cancer, said that vitamin D is thought to cut the body's inflammatory response and stimulate the immune system to work more efficiently, both of which could contribute to a lowered cancer risk. But "we have a big puzzle and this is a tiny piece," he said. "This is a little data point we can plug in . . . but it's still controversial how much vitamin D people should have."
Dr. Michael Choti, a professor of surgery and chief of the division of surgical oncology at the Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins University in Baltimore, also cautioned that more research is needed to identify the risk factors linked with developing pancreatic cancer.
"Certainly this study is hypothesis-generating, but it's not definitive," Choti said. "The concern is that [people] could interpret this as needing to get out in the sun more, when we don't have a good feeling about its negative effects on melanoma or non-melanoma skin cancer. One needs to be careful about making blanket recommendations or even saying that taking vitamin D can reduce the risk of pancreatic cancer."
Studies presented at scientific conferences are not yet peer-reviewed and results are considered preliminary until published in a medical journal.
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