The topical application of demecolcine (Colcemid, N-desacetyl methyl colchicine), N-desacetyl thiocolchicine (Thio-Colciran), and methotrexate preferably in combination, exerts a selectively destructive action on rodent (basal cell) carcinomas, solar keratoses, Bowen's disease, and keratoacanthomas, while sparing surrounding normal tissues.
The former two exert their action by inhibiting mitosis in the metaphase, and the latter inhibits the commencement of mitosis by interference with the synthesis of desoxyribonucleic acid.
The cosmetic results are particularly good when the ears or nose are affected, and the cure rate compares favorably with that resulting from other treatments.
Although ineffective against squamous carcinomas, the fact that this form of therapy is effective for keratoacanthomas could prove a valuable additional diagnostic point between the two in doubtful cases.
BELISARIO JC. Topical Cytotoxic Therapy for Cutaneous Cancer and Precancer. Arch Dermatol. 1965;92(3):293–303. doi:10.1001/archderm.1965.01600150083016