Ovarian cancerExposure to sunlight

Most of the studies relating to sunlight exposure and risk of ovarian cancer are ecological studies conducted in the U.S1 2 3 4.  The two studies by Grant were based on the Atlas of Cancer Mortality Rates in the United States5.  

The geographical variation of ovarian cancer mortality rates in the U.S. is very similar to that for breast cancer, which has strong support as a vitamin D sensitive cancer.  

The geographical variation of July solar UVB dose was used in the U.S as an index of exposure to sunlight.  This index is highly asymmetrical6, being high in the southwest and low in the northeast due to variations in surface elevation and stratospheric ozone layer. 

There are also two multi-country ecological studies7 8.  In Europe, latitude was used as the index of vitamin D7.  In the global multi-country study, calculated solar UVB doses and cloud cover were used for the vitamin D index.

Lower rates of ovarian cancer are seen in areas that have more sunlight.

Indices for other risk modifying factors, such as smoking, alcohol consumption were also used in the United States in studies conducted after 2002 and dietary factors were added to the multi-country studies in order to rule out well-known cancer risk factors that might affect the geographical variation and interpretation of the results.  

In all of these studies, significant inverse correlations between the vitamin D indices and ovarian cancer incidence and/or mortality rate were found.  While a review regarding ovarian cancer concluded that the evidence for UVB and vitamin D was not strong9, it was pointed out in a letter to the editor that most of the observational studies did not consider high enough oral intake or serum 25(OH)D levels and that the ecological studies were in essential agreement about an inverse correlation between solar UVB and ovarian cancer incidence and/or mortality rate10.

A composite death certificate based case-control study found that living in a high UVB dose region of the U.S. was associated with statistically significant reduced risk of ovarian cancer mortality rate, but no statistically significant finding was made with respect to UV dose from occupation or other factor11.

Non-melanoma skin cancer (NMSC) is often an index of high personal solar UVB irradiance.  Thus, it can be used as a long-term vitamin D index in sunnier countries where it is warm enough to expose sufficient skin area while in the sun to produce a reasonable amount of vitamin D. 

A highly significant inverse correlation of ovarian cancer mortality rates with respect to NMSC mortality rates was also found in an ecological study of cancer mortality rates in Spain12. 

A study in Australia, Singapore and Spain found statistically significant reduced incidence of ovarian cancer after incidence of basal cell or squamous cell carcinoma13. 

Page last edited: 18 July 2011

References

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  2. Grant WB An estimate of premature cancer mortality in the U.S. due to inadequate doses of solar ultraviolet-B radiation. Cancer. 2002; 94 (6): 1867-75.
  3. Grant WB An ecological study of cancer mortality rates including indices for dietary iron and zinc. Anticancer Research. 2008; 28 (3B): 1955-63.
  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 Research. 2006; 26 (4A): 2687-99.
  5. Devesa SS, Grauman DJ, Blot WJ, Pennello GA, Hoover RN, Fraumeni JF Jr Atlas of Cancer Mortality in the United States, 1950-1994. 1999;
  6. Leffell DJ, Brash DE. Sunlight and skin cancer. Sci Am. 1996; 275 (1): 52-3.
  7. Grant WB The likely role of vitamin D from solar ultraviolet-B irradiance in increasing cancer survival. Anticancer Res. 2006; 262605-14.
  8. Garland CF, Mohr SB, Gorham ED, Grant WB, Garland FC Role of ultraviolet-B irradiance and vitamin D in the prevention of ovarian cancer. Am J Prev Med. December 2006; 31 (6): 512-514.
  9. Cook LS, Neilson HK, Lorenzetti DL, Lee RC. A systematic literature review of vitamin D and ovarian cancer. Am J Obstet Gynecol. 2010 March 11 [Epub ahead of print]; 203 (1): 70 e1-8.
  10. Grant WB Good evidence exists that solar ultraviolet-B and vitamin D reduce the risk of ovarian cancer. Am J Obstetrics Gynecol. 2010 Jun 2. [Epub ahead of print].;
  11. Freedman DM, Dosemeci M, McGlynn K Sunlight and mortality from breast, ovarian, colon, prostate, and non-melanoma skin cancer: a composite death certificate based case-control study. Occup Environ Med. 2002; 59 (4): 257-62.
  12. Grant WB An ecologic study of cancer mortality rates in Spain with respect to indices of solar UV irradiance and smoking. Int J Cancer. 2007; 1201123-7.
  13. Tuohimaa P, Pukkala E, Scelo G, Olsen JH, Brewster DH, Hemminki K, et al Does solar exposure, as indicated by the non-melanoma skin cancers, protect from solid cancers: Vitamin D as a possible explanation. Eur J Cancer. 2007 May; 29 (43): 1701-1712.