Effect of five antineoplastic agents on tumor xenografts with different growth rates.

The effects of cyclophosphamide (Cy), doxorubicin (Dx), cisplatin (DDP), melphalan (L-PAM), and vincristine (VCR) on various human and animal tumor lines with different growth rates, growing as xenografts in NMRI (nu/nu) mice, were studied. Two types of response were observed: For Cy and Dx, the response of the xenografts was negatively correlated with tumor volume doubling time (TD), indicating that rapidly growing tumors were more sensitive to these drugs than were slowly growing tumors. For DDP, L-PAM, and VCR, the effects were positively correlated with the TD, indicating that slowly growing tumors were more sensitive to these drugs than rapidly growing tumors. The data are discussed in relation to the effects of the drugs on proliferating and nonproliferating cells obtained with other cell lines.