Incidence of Skin Cancer Reaching Epidemic Proportions
Michelle Durkin, BSc
The most common form of cancer today is skin cancer. Approximately half of all new cancers diagnosed are one of three defined types: basal cell carcinoma (BCC) , squamous cell carcinoma (SCC), or malignant melanoma (MM). Although the age of diagnosis is decreasing, most skin cancers do not appear until after the age of fifty, making this disease a serious threat to the elderly population. Fortunately it is also a disease which is successfully treated if detected early.
Epidemiology
The incidence of nonmelanoma (BCC and SCC) and MM skin cancers has increased so significantly over the past few decades it may have reached epidemic proportions, particularly in the United States and Canada. It has been projected by the National Cancer Institute along with the Center for Disease Control that in 1999 alone, skin cancer (all types combined) will claim the lives of nearly 9,200 people in the United States. Besides increasing annual incidence, more women are getting skin cancer and people are getting skin cancer at younger ages.
Individual types of skin cancer follow different morbidity and mortality distributions. About 80% of skin cancers are BCC, 16% SCC, and 4% MM. The mortality rate for nonmelanoma skin cancer is decreasing and that of melanoma is increasing.3 The incidence of melanoma has doubled in Canada in the past twenty years. Although melanoma is still the least common type, it accounts for the greatest percentage of skin cancer deaths making it the most serious type.
There are several risk factors for developing skin cancer. Each factor directly or indirectly influences the frequency of skin cancer occurrence. These factors are listed in Table 1.
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| Age: Increased risk with increased age due to longer total exposure to sunlight as well as an age-related decrease in cellular DNA repair capacity |
Genetics
A definite relationship has been established between the development of skin cancer and sun exposure. Not only do UV rays cause tissue damage by disrupting the genetic material of the cell, they can also damage the skin's normal repair mechanism. In one particular study in New England, over 90% of SCC and more than 50% of BCC contained UV-like mutations in the p53 tumour suppressor gene.1 It was also concluded that sunlight appeared to act as a tumour initiator and promoter, as mutations were not only found in non-melanoma skin cancer, but also their pre-invasive lesions such as actinic keratosis.4
Unfortunately the important role of familial and genetic factors, especially with the most lethal