Rates of reduction in lesion size and grading appear to be significantly better for etretinate than placebo. However, one should be careful of crossover study designs, where a big carry-over effect is likely. If insufficient time is allowed for the etretinate to "wash-out" in those arms where etretinate was given before placebo, then the effects of etretinate were probably confounding the results of the placebo. Long-term efficacy has not been established, but it is unlikely that the long-term efficacy will reflect the efficacy rates reported in the studies, since they reported reduction in AK size. If the AK lesions are not eradicated, they will surely regrow; moreover, even if a particular AK lesion is eradicated, it does not prevent new ones from forming.

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