The effect of 13-cis-retinoic acid chemoprevention on human serum retinol levels

This study of the effect of 13-cis-retinoic acid on serum levels of retinol was a laboratory correlate of a clinical chemoprevention trial in asymptomatic chronic smokers. All study participants had squamous metaplasia of the bronchial epithelium and received 6 months' treatment of either 13-cis-retinoic acid (1 mg/ kg/day) or placebo. Baseline serum retinol levels were compared with levels taken immediately post-treatment. The placebo group (N = 38) had little change, whereas the 13-cis-retinoic acid group (N = 35) experienced a decline in retinol levels (p = 0.06). Within the 13-cis-retinoic acid group, women's (N = 13) mean serum retinol levels dropped significantly, from 531 +/- 191 ng/ml (baseline) to 436 +/- 115 ng/ml (post-treatment) (p = 0.03); men's (N = 22) levels virtually did not change (p = 0.43). Therefore, the borderline-significant overall decline in the 13-cis-retinoic acid group was due entirely to the decline among women subjects. The etiology of this effect is unknown. Our results suggest that chronic 13-cis-retinoic acid administration may lead to a clinically significant reduction in serum retinol levels in females. This finding may have implications for currently ongoing chemoprevention trials that administer 13-cis-retinoic acid for 3 years.