Please note: In 2003, the CTF updated its Grades of Recommendations to include an "I Recommendation" for situations where insufficient evidence exists to allow a recommendation to be made.  (Formerly, these situations were captured under a "C Recommendation".)  This change is not retroactive, and all "C Recommendations" made prior to 2003 have not been reevaluated in light of the new "I" recommendation grade.  For a discussion of these recommendation grades, please link to the 2003 article in the Canadian Medical Association Journal here.

Prevention of Skin Cancer

Objective
To make recommendations about primary and secondary prevention of skin cancer (basal cell carcinoma [BCC], nonmelanomatous skin cancer [NMSC], and malignant melanoma [MM]) among general and high risk populations in Canada.

Burden of Suffering
In Canada in 1992, there were approximately 51,000 new cases of skin cancer. Of these, 47,000 were either basal cell carcinoma (BCC) and squamous cell carcinomas (SCC), commonly referred to as nonmelanomatous skin cancer (NMSC). These skin cancers rarely metastasize and are generally easily treated, but may result in disfigurement and functional impairment if not detected early. An increased risk for NMSC is associated with: a personal history of NMSC, older age, light eyes, skin or hair, poor ability to tan, a high density of freckles, and a marked cumulative lifetime exposure to sun.

Malignant melanoma (MM) differs considerably from these other two skin cancers. While less common, it is far more lethal (MM ranks 14th amongst all cancers in potential years of life lost). In 1993, there were an estimated 2,950 new cases of MM in Canada and in that same year, there were 560 deaths from MM. Risk factors for MM include melanocytic, precursor or marker lesions (e.g. atypical moles, certain congenital moles), increased numbers of common moles, immunosuppression, and a family or personal history of skin cancer, particularly MM. A recent case-control study in Ontario identified four host risk factors associated with MM: red hair, freckled and nevus density and a propensity to sunburn after repeated sun exposure compared to those who tan. Individuals with the rare condition of "familial atypical mole and melanoma" (FAM-M) syndrome, show an increased risk of MM of 100-fold or more. The etiology of both NMSC and MM have been linked to ultraviolet light, particularly UV-B light.

Options
Primary prevention approaches include avoidance of sun during peak periods, use of protective clothing and use of sunscreens. Secondary prevention involves early detection using total body skin examination (TSE) by the physician or patient (p851).

Outcomes
Detection rates, sensitivities, specificities and adverse effects of early detection methods (p852). Measures of the effectiveness of prevention and treatment were tumour thickness, solar keratoses (p854), tanning behaviour and adverse effects (p855).

Evidence
These recommendations were adapted from materials prepared for the 1989 U.S. Preventive Services Task Force (USPSTF). MEDLINE was searched from 1988 to March 1993 using the keywords cancer, skin neoplasm, melanoma, dysplastic nevus, sunscreening agents, isotretinoin and sunlight. Additional articles were identified from the bibliographies of retrieved papers.

Values
The 13-member Task Force of experts in family medicine, geriatric medicine, pediatrics, psychiatry and epidemiology used an evidence-based method for evaluating the effectiveness of preventive health care interventions. Recommendations were not based on cost-effectiveness of options. Patient preferences were not discussed.

Background papers providing critical appraisal of the evidence and tentative recommendations prepared by the chapter author were pre-circulated to the members. Evidence for this topic was presented and deliberated upon in 1- to 2-day meetings, 2 to 3 times per year from January 1993 to June 1993. Consensus was reached on final recommendations.

Benefits, Harms, and Costs
No RCTs exist on the effectiveness of early detection and treatment of MM (p853).

No evidence exists on the sensitivity and specificity of TSE because only persons testing positive are subsequently biopsied. A descriptive study on patient use of a 7-point checklist to evaluate skin lesions reported a sensitivity of 71% and specificity of 99% for MM diagnosis. No data exist on the accuracy of patient detection of lesions, the accuracy of periodic TSE or the efficacy of instructions in reducing TSE errors (p852-3).

Epidemiologic and case-control studies have noted an association between ultraviolet light and MM and NMSC. No RCTs evaluate the effectiveness of sun avoidance and protective clothing in preventing MM and NMSC (p854).

Case-control and cohort studies report no effect, or a significant increased risk of BCC and MM with sunscreen use. Mild to moderate adverse effects of sunscreen occur in 1% to 2% of users, and include contact and photocontact dermatitis, contact urticaria and comedogenicity (p855). There is evidence that solar keratoses may be precursors to NMSC, but the clinical significance of keratoses is unclear. An RCT examining regular use of UV-A- and UV-B-blocking suncreens in persons >40 years who had previous solar keratoses reported that the mean rate of solar keratoses in the control group increased by 1 per subject, and decreased by 0.6 per subject in the sunscreen group at 6 month follow-up (p854).

Recommendations
Recommendation grade [A, B, C, D, E]  and level of evidence [I, II-1, II-2, II-3, III] are indicated after each recommendation. Citations in support of individual recommendations are identified in the guideline text.

• Poor evidence exists to include or exclude (from the PHE) TSE by physicians [C, II-3] or patient self-examination [C, II-3] for early detection of skin cancer in the general population.
• Fair evidence exists to include TSE for individuals at high risk (i.e., first degree relative with MM) [B, II-3].
• Fair evidence (epidemiologic and case-control data, prudence) exists to include counselling to avoid sun exposure at mid-day and to use protective clothing [B, II-2].
• Poor evidence exists to include or exclude advising patients to use sunscreens to prevent NMSC, BCC and MM [C, II-2]. However, fair evidence exists to include recommending sunscreen use for reduction of solar keratoses in persons with a history of solar keratosis who cannot avoid sun exposure [B, I].