Low Oxygen Levels in Prostate Tumors Predict Recurrence

Low oxygen regions in prostate tumors can be used to predict a rise in prostate-specific antigen (PSA) levels, a marker of tumor recurrence in prostate cancer.

In a new study, investigators used a custom-built probe to monitor the amount of oxygen that prostate tumors and noncancerous muscle tissue were receiving. They used this probe on 57 patients with low or intermediate risk of cancer just before the patients received a form of localized radiation therapy. The scientists then tracked the patients over time, looking for a correlation between the amounts of oxygen levels in the prostate tumor relative to the muscle tissue at the time of therapy and later the increase in PSA levels.

Eight of the 57 patients experienced an increase in PSA levels following prostate cancer treatment. Overall, average muscle oxygenation was 12.5-times higher than that of the tumor. Using a statistical model that accounted for such risk factors as tumor grade, PSA level, and tumor size, the team determined that hypoxia was a significant independent predictor of an increase in PSA levels.
In other words, even after accounting for PSA value, Gleason score, tumor size, age, and other prostate cancer risk factors, tumor hypoxia alone could predict the likelihood of increased PSA levels, and potential tumor recurrence.

"Now", said Aruna Turaka, M.D., radiation oncology fellow at Fox Chase Cancer Center (Philadelphia, PA, USA) and lead author on the study, "the goal is to apply the results to the clinic". That, she said, requires a two-pronged approach: developing noninvasive screening methods to identify hypoxic tumors, and more potent anticancer weapons to target them.

"We already knew that there are hypoxic regions within cancers," she said. "The future goal is to interpolate that to relate to the expression of molecular markers [such as hypoxia-inducible factor-1-alpha] and attack those tumors with dose escalation radiation oncology strategies and targeted agents."

The findings were described in a poster presentation at American Society of Clinical Oncology (ASCO) 2009.

Related Links:
Fox Chase Cancer Center
American Society of Clinical Oncology