Vascular occlusion and tumour cell death.

Vascular occlusion has been tested as a means of inducing regrowth delay, local control, reduced cell viability and prolonged alteration of blood flow in mouse tumours. The occlusion has been achieved by applying D-shaped metal clamps across the base of subcutaneously implanted tumours. The period of clamping has been varied from 30 min to 24 hr. Marked tumour regression, delayed growth and long-term tumour control were seen, with the magnitude of the response being proportional to the duration of clamping. Vessel occlusion for at least 15 hr is necessary to achieve local cure of the tumour. The overall effect results partly from an immediate loss of cell viability and partly from a failure of the capillary network to recover its normal perfusion pattern after the clamp has been removed. The implications of this for anti-proliferative endothelial therapy is discussed.