Tumour-cord parameters in two rat hepatomas that differ in their radiobiological oxygenation status

Tumour cords have been examined quantitatively in two rat hepatomas, 3924A and H-4-II-E, that differ in their radiobiological oxygenation status (oxygen enhancement ratio for growth delay [tumour clamped: tumor 'in air'] was 1.35 for 3924A and only 1.08 for H-4-II-E). The average thickness of tumour cords in 3924A was 118 microns and only 69 microns in H-4-II-E. The migration rates across the cords of the two tumours were approximately the same (1.7 and 1.4 micron X h-1) but for any given distance from the subtending blood vessel, the proportion of histologically-dead cells within the cord was always higher for H-4-II-E. Volume for volume, H-4-II-E contained four times as much vascular space as 3924A but it is suggested that the poor quality of this vasculature in H-4-II-E contributed to its relative radioresistance.