Measuring Cancer Therapy Success With Oxygen

The oxygenation of a tumor is critical for the success of cancer treatment. That's because the amount of oxygen in a cell is directly correlated with the ability of that cell to repair radiation damage. When the oxygen level is low, a state called hypoxia, the biological changes in tumor cells produced by radiation -- that will hopefully destroy the cells -- can be repaired, and tumor recurrence is more likely. But when oxygen is present, it reacts with free radical molecules to produce organic peroxide, which causes that damage to be "permanent and irreparable," says study head Jian Z. Wang, Ph.D., an Assistant Professor at OSU and the Director of the Radiation Response Modeling Program at the OSU James Cancer Hospital and Solove Research Institute. Inevitably, those well-oxygenated tumor cells die, tumors are less likely to return, and patient survival rates rise, says Wang.

In their study of 88 women with cervical cancer, Dr. Wang and his colleagues measured the level of hemoglobin, the oxygen-carrying molecule in blood, and measured blood supply to the tumor through magnetic resonance imaging (MRI) scans. Blood tests were conducted weekly beginning prior to treatment, and MRI scans were performed before radiation treatment, during radiation at 2-2.5 and 4-5 weeks, and 1-2 months after treatment. Cancer recurrence rates were tracked for up to 9 years. This study was supported by a NIH R01 grant led by the principal investigator Nina A. Mayr, M.D., Professor of Radiation Medicine at the OSU James Cancer Hospital and Solove Research Institute.

Measurements of tumor oxygenation just 2 weeks into treatment provided the best predictor of tumor control and disease-free survival. That early glimpse into the future can identify individuals at the greatest risk of having their cancer return, Mayr says, giving doctors the opportunity to adopt more aggressive therapies to improve the prognosis. Wang predicts that, with further testing, the technique also will prove useful for other types of cancer.

The research was described in the talk, "When the Oxygen Level Matters Mostly During Radiation Therapy of Cervical Cancer?" presented July 31, 2008 at the 50th annual meeting of the American Association of Physicists in Medicine.