CORRESPONDENCE

Re: Sun Exposure and Mortality From Melanoma

Thomas R. Fears, Margaret A. Tucker

Affiliation of authors: Division of Cancer Epidemiology and Genetics, National Cancer Institute, National Institutes of Health, Bethesda, MD

Correspondence to: Thomas R. Fears, PhD, National Cancer Institute, Executive Plaza South, Rm. 8040, Bethesda, MD 20892 (e-mail: fearst{at}epndce.nci.nih.gov).

Berwick et al. (1) observed that increased sun exposure is associated with increased survival from melanoma, based on 528 case subjects. The estimated association is certainly strong (patients with solar elastosis, multivariable hazard ratio = 0.4, 95% confidence interval [CI] = 0.2 to 0.8), and it creates a serious dilemma because increased sun exposure is also associated with increased risk for melanoma incidence.

We recently showed, in patients with invasive cutaneous melanoma from clinics in Philadelphia and San Francisco, that individual risk was associated with the individual's history of exposure to levels of midrange UV radiation (UVB flux). A 10% increase in average annual UVB flux was associated with an increased odds ratio (OR) for melanoma (for males, OR = 19%, 95% CI = 5% to 35%; for females, OR = 16%, 95% CI = 2% to 32%) (2).

The association for individuals is reflected in population data by the relationship of melanoma incidence with latitude and, implicitly, UVB flux (3,4). This relationship has long been recognized and can be seen using incidence data from the National Cancer Institute's Surveillance, Epidemiology and End Results (SEER) program. We plotted the age-adjusted incidence of melanoma (1992–2001) for male and female non-Hispanics for the 11 SEER locations (Fig. 1). The estimated age-adjusted melanoma rates for males and females varied from 17.4 to 44.6 cases per 100 000 between the locations of lowest and highest UVB flux.



View larger version (13K):
[in this window]
[in a new window]
 
Fig. 1. Age-adjusted rates (1992–2001) of melanoma versus UVB flux among non-Hispanic males and females in the 11 Surveillance, Epidemiology and End Results (SEER) locations. UVB flux is a measure of the biologic activity of radiant energy received per unit area, and one count corresponds to approximately 0.068 mJ/cm2. Analysis of variance from linear regression, R2 = 0.82; two-sided P<.001.

 
We considered whether the individual association of sun exposure and survival from melanoma observed by Berwick et al. is reflected in the SEER population survival data. The SEER program normally uses relative survival (the ratio of the observed overall survival to the expected survival) to deal with errors in cause of death classification (57). Based on 32 911 patients from the 11 SEER locations, for females (n = 14 838), the relative 3- and 5-year survival rates were 91%–97% and 88%–95%, respectively; for males (n = 18 073), the relative 3- and 5-year survival rates were 87%–93% and 82%–91%, respectively (Fig. 2). Regression estimates for the change in expected relative survival between the location of highest flux and the location with lowest flux were 1.7 percentage points or less. We found no evidence for an association between relative survival and UVB flux.



View larger version (17K):
[in this window]
[in a new window]
 
Fig. 2. Relative survival rates versus UVB flux among non-Hispanic females and males in the 11 Surveillance, Epidemiology and End Results (SEER) locations (1992–1999). Three-year (dots with solid lines) and 5-year (circles with hatched lines) survival rates are shown for A) female and B) male melanoma case patients. Analysis of variance from linear regression: for females, R2 = .06, P = .47 and R2 = .01, P = .84 for 3- and 5-year survival, respectively; and for males, R2 = .02, P = .67 and R2 = .01, P = .82 for 3- and 5-year survival, respectively.

 
Following Berwick et al., we considered only the 24 888 patients with localized tumors and excluded lentigo malignant melanoma for our analysis. Overall, the 3- and 5-year relative survival rates were 96%–100% and 91%–99%, respectively. We found no evidence for an association between relative survival and UVB flux. The estimated change in relative survival between the location with the highest UVB flux and that with the lowest was 1.4 percentage points or less. We also considered the 4386 patients with distant or regional stage of disease at diagnosis. Overall, the 3- and 5-year relative survival rates were 88%–93% and 81%–88%, respectively. Again, we found no evidence for an association between relative survival and UVB flux. The estimated changes in relative survival between the location with the highest UVB flux and that with the lowest were 2.3% at 3 years and 3.3% at 5 years.

It appears that, unlike the association between sun exposure and melanoma risk, the association between sun exposure and survival for melanoma patients is not reflected in the SEER populations. There are, of course, possible explanations, e.g., UVB flux may not be the appropriate measure of population sun exposure for survival of melanoma patients. However, our findings do introduce a note of caution in the interpretation of the findings of Berwick et al. Specifically, it is important to discourage those who would seek sun exposure in the hope of improving survival after melanoma occurrence. Rather, it is most important to continue to strongly encourage people to avoid the sun to reduce the risk of melanoma occurrence.

REFERENCES

(1) Berwick M, Armstrong BK, Ben-Porat L, Fine J, Kricker A, Eberle C, et al. Sun exposure and mortality from melanoma. J Natl Cancer Inst 2005;97:195–9.[Abstract/Free Full Text]

(2) Fears TR, Bird CC, Gail MH, Guerry D, Sagebiel RW, Elder DE, et al. Average UVB intensity and time outdoors predict melanoma risk. Cancer Res 2002;62:3992–6.[Abstract/Free Full Text]

(3) Lancaster H. Some geographical aspects of the mortality from melanoma in Europeans. Med J Aust 1956;1:1082–7.

(4) Armstrong BK. Melanoma of the skin. Br Med Bull 1984;40:346–50.[ISI][Medline]

(5) Boer R, Ries L, van Ballegooijen M, Feuer EJ, Legler J, Habbema D. Ambiguities in calculating cancer patient survival: the SEER experience for colorectal and prostate cancer. Bethesda (MD): Statistical Research and Applications Branch, National Cancer Institute, 2002 Report No: Technical Report 2002–05.

(6) Brown BW, Brauner C, Minnotte, MC. Noncancer deaths in white adult cancer patients. J Natl Cancer Inst 1993;85:979–87.[Abstract]

(7) Percy CL, Miller BA, Gloeckler Ries LA, Effects of changes in cancer classification and the accuracy of cancer death certificates on trends in cancer mortality. Ann N Y Acad Sci 1990;609:87–97; discussion 97–9.[ISI][Medline]


This article has been cited by other articles in HighWire Press-hosted journals:


Response to this Correspondence

             
Copyright © 2005 Oxford University Press (unless otherwise stated)
Oxford University Press Privacy Policy and Legal Statement