Effect of microenvironmental factors on the response of cells to single and fractionated heat treatments.

The thermal sensitivity of cells is substantially influenced by variations in the concentration of hydrogen ions, glucose, and oxygen under certain conditions. The clinical significance of these observations is based on the reported differences in concentration of these metabolites in normal and tumor interstitial fluid. In general, tumor-like nutritional conditions sensitize cells to hyperthermia. However, these sensitizing effects may be cell line and temperature dependent and may be modified by fractionated heat treatments. Data relevant to these considerations are reviewed and their clinical relevancy is discussed.