AN ANALYSIS OF SYSTEMIC TUMOR OXYGENATION USING MULTI-REGION MODELS

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Abstract
Transient solutions are presented for multi-region models that previously have been shown to describe oxygen tension profiles in human tumors under normoxia. Model parameter estimations used in the oxygenation simulation are based on clinically measured steady-state pO2/ profiles. The transient behavior would result from increasing systemic oxygen levels through either respiratory hyperoxia or whole body exposure to pure O2 atmospheres at normobaric or hyberbaric pressures. The time constant for systemic oxygenation of the underlying stroma is rapid compared to that of the tumor. The predictions of the final steady-states that result from systemic oxygenation are dependent on the kinetic rate form used for characterising oxygen consumption via cell respiration. However, the predictions are consistent with literature data that have been reported from animal model studies. Regardless of which rate form is employed, the transient results indicate the time-scale for tumor oxygenation is considerably longer than that typically employed in previous clinical studies investigating the role of oxygen in tumor response to radiotherapy. This suggests that more chronic oxygenation maneuvers may lead to improved therapy.