Solar ultraviolet-B doses/vitamin D and ethnic heritage play important roles in breast and prostate cancer incidence rate variations, respectively William B. Grant, Sunlight, Nutrition and Health Research Center (SUNARC) 21 April 2010 Sir: The paper on spatial trends of breast and prostate cancer incidence rates in the United States  presents interesting data but overlooks a significant portion of the literature on ecological studies of cancer mortality rates in the United States related to solar ultraviolet-B (UVB) doses and other risk modifying factors. A set of such papers is provided here published prior to submission of this paper [2-5]. In addition, there have been more since that paper was submitted [6,7]. These and other ecological studies have been reviewed recently [8,9]. The role of vitamin D in reducing risk of cancer has also been reviewed recently [10,11]. Other factors included in the ecological studies of white Americans [3-7] were air pollution, alcohol consumption, dietary iron and zinc, Hispanic heritage, smoking, urban/rural residence, and viral infections. As noted in , the patterns for breast and prostate cancer have similarities and differences. One of the similarities is related to increased risk for those eating the Western diet [12,13]. However, one of the differences is that vitamin D is not associated with reduced risk of prostate cancer incidence  although it is associated with reduced case-fatality rate . Having studied the geographical variation of prostate cancer mortality rates in the United States for a decade, my research turned in a new direction after finding the map of country of greatest ancestry by county in the United States for the year 2000 . Many of the features correlated very closely with features in the prostate cancer mortality map . This finding led to the hypothesis that ethnic background played a very important role in the etiology of prostate cancer and to a paper in which it was proposed that prevalence of Apolipoprotein E 4 was an important risk factor and supported by a multi-country ecological study . Prostate cancer is the only cancer for which cholesterol is a risk factor . This hypothesis will be investigated by researchers who have ongoing cohort studies with tissue samples that can be used for DNA analysis. References 1. Mandal R, St-Hilaire S, Kie JG, Derryberry D. Spatial trends of breast and prostate cancers in the United States between 2000 and 2005. Int J Health Geogr. 2009, 8:53. 2. Garland FC, Garland CF, Gorham ED, Young JF. Geographic variation in breast cancer mortality in the United States: a hypothesis involving exposure to solar radiation. Prev Med. 1990, 19(6):614-622. 3. Grant WB. An ecologic study of dietary and solar ultraviolet-B links to breast carcinoma mortality rates. Cancer. 2002, 94(1):272-281. 4. Grant WB, Garland CF. The association of solar ultraviolet B (UVB) with reducing risk of cancer: multifactorial ecologic analysis of geographic variation in age-adjusted cancer mortality rates. Anticancer Res. 2006, 26(4A):2687-2699. 5. Grant WB. Hypothesis-Ultraviolet-B irradiance and vitamin D reduce the risk of viral infections and thus their sequelae, including autoimmune diseases and some cancers. Photochem Photobiol. 2008, 84(2):356-365. 6. Grant WB. An ecological study of cancer mortality rates including indices for dietary iron and zinc. Anticancer Res. 2008, 28(3B):1955-1963. 7. Grant WB. Air pollution in relation to U.S. cancer mortality rates: An ecological study; likely role of carbonaceous aerosols and polycyclic aromatic hydrocarbons. Anticancer Res, 2009, 29(9):3537-3545. 8. Mohr SB. A brief history of vitamin D and cancer prevention. Ann Epidemiol. 2009, 19(2):79-83. 9. Grant WB, Mohr SB. Ecological studies of ultraviolet B, vitamin D and cancer since 2000. Ann Epidemiol. 2009, 19(7):446-454. 10. Grant WB. How strong is the evidence that solar ultraviolet B and vitamin D reduce the risk of cancer? An examination using Hill’s criteria for causality. Dermato-Endocrinology. 2009, 1(1):17-24. 11. Grant WB. A critical review of Vitamin D and Cancer: A report of the IARC Working Group on vitamin D. Dermato-Endocrinology. 2009, 1(1):25-33. 12. Grant WB. An ecologic study of dietary and solar ultraviolet-B links to breast carcinoma mortality rates. Cancer. 2002, 94(1):272-281. 13. Grant WB. A multicountry ecologic study of risk and risk reduction factors for prostate cancer mortality. Eur Urol. 2004, 45(3):271-279. 14. Gupta D, Lammersfeld CA, Trukova K, Lis CG. Vitamin D and prostate cancer risk: a review of the epidemiological literature. Prostate Cancer Prostatic Dis. 2009, 12(3):215-226. 15. Tretli S, Hernes E, Berg JP, Hestvik UE, Robsahm TE. Association between serum 25(OH)D and death from prostate cancer. Br J Cancer. 2009, 100(3):450-454. 16. Brittingham A, de la Cruz GP. Ancestry 2000. Census 2000 Brief CK2BR-35. U. S. Dept. of Commerce, Census Bureau. Washington, DC. 2004, p. 9. http://www.census.gov/prod/2004pubs/c2kbr-35.pdf (accessed December 16, 2009) 17. Devesa SS, Grauman DJ, Blot WJ, Pennello GA, Hoover RN and Fraumeni JFJ. Atlas of Cancer Mortality in the United States, 1950-1994. NIH Publication No. 99-4564. National Institute of Health, 1999. http://www3.cancer.gov/atlasplus/type.html (accessed April 21, 2010) 18. Grant WB. A multicountry ecological study of risk-modifying factors for prostate cancer: Apolipoprotein E 4 as a risk factor and cereals as a risk reduction factor. Anticancer Res. 2010, 30:189-199. 19. Iso H, Ikeda A, Inoue M, Sato S, Tsugane S. Serum cholesterol levels in relation to the incidence of cancer: The JPHC Study Cohorts. Int J Cancer. 2009, 125(11):2679-2686. Competing interests Disclosure I receive funding from the UV Foundation (McLean, VA), the Sunlight Research Forum (Veldhoven), Bio-Tech-Pharmacal (Fayetteville, AR), and the Vitamin D Council (San Luis Obispo, CA), and have received funding from the Vitamin D Society (Canada).