Cyclophosphamide-induced sister chromatid exchanges in patients with nephrotic syndrome

Frequency of sister chromatid exchanges (SCE) of peripheral blood lymphocytes was used for assessing chromosome damage induced by cyclophosphamide (CY) in patients with primary nephrotic syndrome. A significant rise in SCE was seen in all patients on a standard 6- to 8-week CY regimen at the beginning of the first week of treatment. When CY was discontinued, a gradual decline in SCE was noted which returned to a normal limit within 4-6 months after discontinuation of the drug. In patients treated previously (mean follow-up 9.6 years, range 1.5-17.5 years) with high doses of CY (mean total dose 380 mg/kg, range 120-1,999) or in patients on steroid therapy, frequency of SCE was not significantly different from control subjects. We concluded that SCE analysis did not reveal any evidence suggesting that the dosage of CY used in this study had induced a permanent genetic damage. However, further follow-up of patients who had received the largest total doses of drug is required.