Sister chromatid exchanges in lymphocytes of a patient treated with cyclophosphamide and vincristine for non-Hodgkin's lymphoma.

Sister chromatid exchanges (SCEs) were investigated in lymphocytes from an adult patient treated with cyclophosphamide (CTX) and vincristine (VCR) for non-Hodgkin's lymphoma. The treatment consisted of iv injection of CTX (1 g) followed immediately by injection of VCR (2 mg). The patient was treated six times at weekly intervals, except for two irregular intervals of 35 and 48 days, respectively, as the second and the fourth intervals. Before the initiation of the therapy, the SCE frequency in the patient was 9.9 +/- 3.5 per cell, which is not significantly different from those of healthy controls and other cancer patients not given chemotherapy. After the first injection, the SCE frequency increased rapidly with time, reaching a peak of 33.4 +/- 4.6 per cell in 24 hr, and then gradually decreased, returning to a nearly normal level of 12.5 +/- 4.2 per cell on the 7th day. Similar cycles of rapid increase and slow decrease in the SCE frequency were observed after each of the subsequent five injections, resulting in a gradual rise in the basal and the maximal levels of the SCE values. Oral administration of CTX (150 mg/day) for about a month during the second interval slightly increased the SCE value from 16.1 +/- 3.1 to 22.4 +/- 6.2 but injections of vincristine alone at a dose of 2 mg twice during the fourth 45-day interval did not affect the gradually decreasing trend in the SCE frequency. In the 5th month after the termination of the therapy, the SCE value returned to the untreated level.