Dynamic breast tumor oximetry: The development of prognostic radiology

A novel pre clinical approach to evaluating tumor oxygen dynamics was recently introduced (Am. J. Clin. Oncol. 24, 462-466 (2001)). FREDOM (Fluorocarbon Relaxometry using Echo planar imaging for Dynamic Oxygen Mapping) allows maps of tumor pO₂ including 50-150 individual locations simultaneously to be produced with typical in plane resolution of 1.25 mm in 6.5 mins. The technique has been applied extensively in rat prostate tumors and is now demonstrated in the rat breast 13762NF adenocarcinoma. When anesthetized rats breathed 33% oxygen, mean baseline pO₂ was in the range 17 ± 2 (se) torr to 74 ± 4 torr with mean value for nine tumors 46 ± 8 torr. However, small tumors (< 2.2 cm³) were significantly better oxygenated with mean pO₂ = 63 ± 7 torr than large tumors (> 2.4 cm³) with mean pO₂ 24 ± 5 torr (p< 0.002). Switching the inhaled gas to oxygen or carbogen produced a significant and rapid increase in mean pO₂ for both small and larger tumors (p< 0.05). Given the increasing evidence that tumor oxygenation is related to therapeutic outcome, we believe this approach to measuring tumor oxygen dynamics can be of value in predicting response to therapy, evaluating adjuvant interventions designed to modulate response to therapy, and in providing "Prognostic Radiology".