Tumor necrosis and oxygen status were investigated as a function of tu
mor size in three syngeneic murine carcinomas, MCa-4, OCa-I, and SCC-V
II, in C3Hf/Kam mice. Tumor necrosis was estimated histologically, and
tumor oxygenation determined by direct polarographic histography. As
tumor volume increased necrosis increased significantly in all three t
umor types (p < 0.001). Similarly, as tumor volume increased from 200
to 1 400 mm(3), hypoxia, defined as the percentage of measured pO(2) v
alues less than or equal to 5.0 mm Hg, increased from 55.1% to 95.9%,
70.3% to 81.4%, and 56.8% to 98.5% in MCa-4, OCa-I, and SCC-VII tumors
respectively (p < 0.001). Correcting pO, for necrosis reduced the tum
or size dependence of measured tumor hypoxia in all three tumor types
but in no case was the reduction significant. The main effect of corre
ction was to shift the fitted curves of percent pO(2) values less than
or equal to 5.0 mm Hg down toward lower percentages for all tumors. T
his change was significant for MCa-4 and OCa-I tumors (p < 0.001), but
not for SCC-VII (p = 0.054). Defining the influence of variables such
as necrosis that affect polarographic assessment of tumor oxygenation
is important to enhance the technique's reliability and prospect as a
n investigative and predictive tool.