Primary myelodysplastic syndrome: treatment of 6 patients with 13-cis retinoic acid.

6 patients with primary MDS were treated with 20 mg/m2 13-cis retinoic acid (13-RA) (RoacutaneR, Roche, Basel) daily for 6 weeks and with an additional 100 mg/m2 daily for 4 weeks (3 patients). 4 patients responded either with an increase in peripheral blood neutrophil count (2 patients) or with a decrease in MPO-deficient neutrophils (2 patients). These effects were not seen until 3 weeks after the onset of the treatment and they were accompanied by an increase in the growth of day 11 granulocytemonocyte colonies, and, in the patients showing clonal cytogenetic abnormalities, by a disappearance of minor clonal abnormalities during the treatment. These findings may be the result of a stimulation of the growth of normal or only slightly defective bone marrow progenitor cells in combination with a differentiational effect. The clinical side effects were limited to hyperkeratosis and dryness of mucous membranes in 5 patients. I patient developed a dermatitis. None showed signs of hepatotoxicity. Because of the pronounced subjective discomfort experienced by the patients receiving 100 mg/m2, it seems recommendable to treat patients with MDS with low dosages of 13-RA (10 to 20 mg/m2) for longer periods (3–6 months) in order to evaluate the effect of 13-RA on the long term basis.