Abstract
Phosphorus metabolite ratios were measured using ^31^P magnetic resonance spectroscopy shortly before measurement of cell survival and radiobologic hypoxic fraction (HF) in EMT6/SF tumors, transplanted into a hindlimb of Balb/c mice. A total of 58 tumors with a volume range of 180 to 1250 mm^3^ were examined in experiments entailing no anesthesia. Postirradiation tumor cell viability was measured using an in vitro clonogenic assay. Correlations between tumor volume, surviving fraction (SF), HF, phosphorus metabolite ratios, and intracellular pH were computed. Both SF and HF increased significantly with tumor volume as did the metabolite ratios of inorganic phosphorus and phosphomonoesters to nucleoside triphosphates (P~i~/NTP and PME/NTP, respectively), as well as P~i~ to phosphocreatine (Pi/PCr). In comparison to HF, the ratios of P~i~NTP, P~i~,/PCr, and PME/NTP each yielded significant positive correlations (Kendall correlation coefficients (ฯ) = 0.25 to 0.33). However, these were not significantly stronger than the correlation between HF and volume (ฯ = 0.21). Apparent values of tumor pH did not correlate with any other measured parameter. While these results indicate a statistical relationship between HF and the measured metabolite ratios, the widely scattered data, as reflected by |ฯ| < 0.35, made metabolite ratios poor predictors of HF in individual tumors. ยฉ 1992 Academic Press, Inc.