Therapeutic response of human lung tumour xenografts to cyclophosphamide

The effect of cyclophosphamide, given as a single i.p. injection (240 mg/kg) on 13 various fast growing human lung tumours, transplanted and passed serially in athymic nude mice, were studied. Cyclophosphamide showed activity against all tumours studied. The sensitivity of the different tumour lines tested varied considerably. The faster a tumor was growing, the more pronounced was the inhibitory effect of cyclophosphamide on growth, independent of the histological type. If different lung tumours were treated at the same size and site (8-10 mm, s.c. right anterior flank), growth rate was a factor of decisive importance for the sensitivity of a tumour to cyclophosphamide.