2. Retinoids (e.g., etretinate, isotretinoin, tazarotene, tretinoin, adapalene) systemically or topically, or > 5% of an alphahydroxy acid (e.g., glycolic acid, lactic acid), photodynamic therapy (PDT), or 5-fluorouracil or imiquimod (except as topical treatment to discrete BCCs) systemically or topically to the skin during the six months prior to entry.