The author does not state how many studies were examined, but from a hand count there were approximately 17 for primary prevention and approximately 30 for secondary prevention interventions.
For primary prevention the following was found:
One RCT (588 adults during one summer) demonstrated the effectiveness of sunscreens in the prevention of solar keratoses (mean difference 1.53 keratoses, 95% confidence interval: 0.81, 2.25).
There is reasonably strong evidence that knowledge about skin cancer can be enhanced by health education or promotion interventions, such as leaflet or poster campaigns targeted at the young female population and educational programmes aimed at schoolchildren. However, evidence that sun exposure behaviour can be altered is very weak, with no UK studies being able to demonstrate such an effect.
In one RCT, 1,800 participants with a history of non-melanoma skin cancer received either 50 mg beta carotene daily or a placebo. The probability of developing a new non-melanoma skin cancer was not significantly different between the groups during 5 years follow-up.
Effectiveness of low-dose isotretinoin (10 mg daily) on the prevention of recurrence of basal cell carcinoma was assessed in a RCT: 981 patients were followed-up for 6 months to 3 years, and there was no significant difference between the isotretinoin and the placebo groups in the cumulative incidence of new lesions.
For secondary prevention, the evidence regarding the effectiveness of screening for skin cancer is incomplete. The available evidence is either descriptive or of a quasi-experimental design.