LAKE TAHOE, Nev. -- High levels of ultraviolet radiation at an individual's birth location, sun-sensitive skin type and a history of skin cancer each decreased risk for pancreatic cancer, according to study results presented at the American Association for Cancer Research's Pancreatic Cancer: Progress and Challenges conference, held here June 18-21.
Rachel Neale, Ph.D., principal investigator at Queensland Institute of Medical Research in Queensland, Australia, presented the results of a population-based, case-control study that adds to the already conflicting data about sun exposure, vitamin D gained from sun exposure and cancer risk.
"Several ecological studies, including one conducted in Australia, have suggested that people living in areas with high sun exposure have lower risk for pancreatic cancer," Neale said. "However, some studies of circulating vitamin D indicate that people with high vitamin D are at increased risk, and one study of vitamin D intake supports this increased risk."
The results of this study support the existing ecological data which indicate that sun exposure has a protective effect against pancreatic cancer.
Neale and colleagues recruited 714 people in Queensland, Australia, between 2007 and 2011. They were matched by age and sex to 709 control participants. All participants were interviewed about socio-demographic information and medical history. In addition, they were asked about the location of their birth, skin cancer history and skin type, defined by skin color, tanning ability and propensity to sunburn.
Using NASA's Total Ozone Mapping Spectrometer, the researchers assigned a level of ultraviolet radiation to each birth location and then split them into thirds based on how much radiation was present.
Participants born in areas with the highest levels of ultraviolet radiation had a 24 percent lower risk for pancreatic cancer compared with those born in areas of low ultraviolet radiation.
In addition, although all skin types had some significant association with pancreatic cancer risk, those classified as having the most sun-sensitive skin had a 49 percent decreased risk for pancreatic cancer compared with those classified as having the least sun-sensitive skin. Finally, participants with a history of skin cancer or other sun-related skin lesions had a 40 percent lower risk for pancreatic cancer than those who had not reported skin lesions.
"There is increasing interest in the role of sun exposure, which has been largely attributed to the effect of vitamin D, on cancer incidence and mortality," Neale explained. "It is important that we understand the risks and benefits of sun exposure because it has implications for public health messages about sun exposure, and possibly about policy related to vitamin D supplementation or food fortification."
Moving forward, Neale recommended that researchers conduct large cohort studies that measure sun exposure comprehensively, and serum vitamin D.
"There are several trials of vitamin D that are either under way or planned, and pooling data from these might give some clue about vitamin D and pancreatic cancer," Neale said.
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Abstract: Association between ambient ultraviolet radiation at birth, skin type, skin cancer history and pancreatic cancer. Rachel E. Neale1, Bich Tran1, David C. Whiteman1, Penelope M. Webb1, Jonathan Fawcett2, Lin Fritschi3, Harvey Risch4. 1Queensland Institute of Medical Research, Brisbane, Qld, Australia, 2The University of Queensland, Brisbane, Australia, 3Western Australian Institute for Medical Research, Perth, Australia, 4Yale School of Public Health, New Haven.
Background: Ecological studies suggest that people living in areas with lower ambient sunlight are at higher risk of pancreatic cancer. However these studies have major limitations and there have been few attempts in observational studies to assess the association between measures of sun exposure and pancreatic cancer. Moreover, the results from the ecological studies have been attributed to differences in circulating vitamin D, but several cohort studies have suggested that people with higher serum 25 hydroxy vitamin D are at higher rather than lower risk of pancreatic cancer. This is clearly an area which requires further exploration.
Methods: We undertook a population-based case-control study in Queensland, Australia between 2007 and 2011. We recruited 704 cases and 709 age- and sex-matched controls. Participants were asked to undergo an interview in which we captured sociodemographic, medical history and lifestyle information, as well as information about location of birth, skin cancer history and skin type (measured as skin colour, tanning ability and propensity to burn). We used NASA's Total Ozone Mapping Spectrometer (TOMS) to assign an ambient ultraviolet radiation (UVR) value to each location of birth, and divided this into tertiles. Multivariable logistic regression analyses were used to identify associations between UVR at birth, skin type and self-reported skin cancer history.
Results: Approximately 60% of both cases and controls were men and the mean age of all participants was 67. People born in areas with high UVR were at lower risk of pancreatic cancer than those born in an environment with low UVR (OR highest versus lowest UVR tertile 0.76, 95% CI 0.56-1.01 (adjusted for age, sex, smoking, diabetes, BMI and alcohol use)). All measures of skin type were significantly associated with pancreatic cancer risk, with those with the most sun sensitive skin being at approximately half the risk of those with the least sun-sensitive skin (for example, comparing those who burn badly with those who don't burn at all: adjusted OR 0.51, 95% CI 0.36-0.73). People who had been diagnosed with skin cancer or other sun-related skin lesions had a 40% lower risk of pancreatic cancer than those who had not had skin lesions treated (OR 0.60, 95% CI 0.48-0.75).
Conclusions: These findings support several ecological studies showing that exposure to high UVR confers a lower risk of pancreatic cancer. Given the findings of the studies examining circulating vitamin D, it is possible that if exposure to UVR does decrease risk of pancreatic cancer it is acting independently of vitamin D. Understanding the potentially complex role of UVR in pancreatic cancer needs further study, as this may provide an avenue for preventive strategies.