Cutaneous malignant melanoma (CM) is much more life threatening than BCC or SCC. The CM rate increased in the U.S. from 6.8/100,000 in 1973 to 17.4/100,000
in 1999 (Saraiya et al., 2004), and to an average of 19.4/100,000 from 2001 to 2005 (National Cancer Institute, http://seer.cancer.gov/statfacts/html/melan.html). It has been noted for many years that melanoma rates tend to be higher at lower latitudes, following the trend toward a higher incidence of solar radiation with decreasing latitude (Whiteman and Green, 1999).
It has been estimated that 65% to 90% of melanoma cases have been caused by exposure to the sun (Saraiya et al., 2004) with a higher estimated percentage of 95% occurring in Australia (Australian and New Zealand Bone and Mineral Society et al., 2005). One of the remarkable recent findings is that solar elastosis, a histologic indicator of cutaneous sun damage, has been positively associated with melanoma survival (Berwick et al., 2005), suggesting that people with melanoma who have had the most sun exposure have higher survival rates than those with less sun exposure. These observations raise the possibility that high amounts of vitamin D that result from high sun exposure may also increase melanoma survival. However, Berwick et al. (2005) state that other factors could be attributed to the increased survival rate among people with the highest sun exposure; for example, the association between sun exposure and early detection of melanoma.
Some reports suggest that CM is related to intermittent extreme sun exposure (Melville et al., 1991; Weinstock, 1993) rather than to cumulative exposure over long time periods. This is consistent with the fact that melanoma incidence tends to be higher of indoor workers than of outdoor workers (Koh and Lew, 1994), though it could also be consistent with indoor workers having low amounts of vitamin D. People diagnosed with melanoma often do have low vitamin D levels (Egan et al., 2005). Additionally, high exposure to the sun during childhood and early youth seems to positively correlate with CM incidence (Weinstock, 1993), particularly for those who suffered blistering sunburns. If sunburn is the primary cause of melanoma, then higher rates would be expected in mid-latitude U.S. regions where sunburn rates are highest among Caucasians (Saraiya et al., 2002).
An early study suggested that UV-A may be important in CM (Setlow, 1974). If so, there are a number of consequences. Some investigators hypothesize that the risk of melanoma may have increased because until recently, sunscreens blocked only UV-B and not UV-A. The suggestion is that blocking only UV-B is detrimental in part because UV-B causes the body to produce vitamin D, which may protect against melanoma (Garland et al., 1992). If the majority of solar-induced melanomas are caused by UV-A, then malignant melanoma will not be affected to any major extent by stratospheric ozone loss. Additionally, shade would be more important for melanoma prevention, because UV-A penetration is less than UV-B penetration into shaded areas (Grant and Heisler, 2001).
Higher incidence of CM has been assumed to be a result of increased UV due to ozone depletion (Madronich and De Gruiji, 1993). A 1996 examination of the effect of the Montreal Protocol and its amendments (Slaper et al., 1996) concluded that although UV-B would peak near the year 2000, skin cancer rates will continue to increase into the middle of the present century; approximately 10% higher than in 1976. By 2100, the Slaper study concluded that CM incidence rates would return to the 1976 levels.
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Complete Guide to Preventing Skin Cancer. We all know enough to fear the name, just as we do the words tumor and malignant. But apart from that, most of us know very little at all about cancer, especially skin cancer in itself. If I were to ask you to tell me about skin cancer right now, what would you say? Apart from the fact that its a cancer on the skin, that is.