Factors responsible for bone marrow toxicity after treatment of myeloma patients with different alkylating agents

Leukopenia and thrombocytopenia were studied after loading doses of melphalan (5 mg/daily for 18-25 days) in 71 myeloma patients. Seventy per cent of the patients developed pronounced leukopenia (white cells less than 2.0 X 10(9)/l) and/or thrombocytopenia (platelets less than 100 X 10(9)/l). The patients with pronounced and moderate hematological side-effects, respectively, were compared for weight and age. The body weight was the same in the two groups, indicating that the patient's weight is of minor importance for the dosage of melphalan. There was a numerical difference in age, on the borderline for statistical significance, indicating that the age of the myeloma patient may be of minor importance for the dosage of melphalan. It is possible that more pronounced age differences may be of greater importance in this respect. Fifteen patients with myeloma were treated with cyclophosphamide. Compared with melphalan, the effect on white cells was the smae, while the incidence of thrombocytopenia was statistically significantly lower with cyclophosphamide.