To confirm reports that
skin cancer can be prevented with
retinoids, we conducted a three-year controlled prospective study of oral
isotretinoin (also called
13-cis retinoic acid) in five patients with
xeroderma pigmentosum who had a history of multiple cutaneous basal-cell or
squamous-cell carcinomas. Patients were treated with
isotretinoin at a dosage of 2 mg per kilogram of
body weight per day for two years and then followed for an additional year, without the
drug. Before, during, and
after treatment, biopsies of all suspicious lesions were performed, and
skin cancers were surgically removed. The patients had a total of 121
tumors (mean, 24; range, 8 to 43) in the two-year interval before treatment. During two years of treatment with
isotretinoin, there were 25
tumors (mean, 5; range, 3 to 9), with an average reduction in
skin cancers of 63 percent (P = 0.019). After the
drug was discontinued, the
tumor frequency increased a mean of 8.5-fold (range, 2- to 19-fold) over the frequency during treatment (P = 0.007). Although all patients experienced mucocutaneous toxic effects, and
triglyceride, liver-function, or skeletal abnormalities developed in some, high-dose oral
isotretinoin was effective in the
chemoprophylaxis of
skin cancers in patients with
xeroderma pigmentosum.