Tumor volumes in athymic nude mice bearing subcutaneously xenografted Caki-I carcinomas during treatment with the GH-RH antagonist MZ-4-71 administered at a dose of 20 μg B.I.D. per animal, s.c. Treatment was started when the tumors measured approximately 24–27 mm3 and lasted for 4 weeks. Vertical bars represent standard error, ∗, P < 0.5 versus control, ∗∗, P < 0.01 versus control.