Low-oxygen regions in prostate tumours can be used to predict the recurrence of cancer in a patient, say scientists.
Researchers at the Fox Chase Cancer Center came to this conclusion after analysing the observations made during a long-term study, whose results will be presented at the 2009 American Society of Clinical Oncology annual meeting in Orlando, Florida.
Dr. Aruna Turaka, a radiation oncology fellow and the lead author of the study, says that low oxygen is a well-known risk factor for radiation resistance in solid tumours.
She says that the current study reinforces the preliminary findings of the six research papers published between 2000 and 2002, which detailed the link between low oxygen in tumours and the risk of increased prostate-specific antigen (PSA) levels.
During the study, her team used a custom-built probe to monitor the amount of oxygen that prostate tumours and non-cancerous muscle tissue were receiving.
The researchers used this probe on 57 patients with low or intermediate risk of cancer just before the patients received a form of localized radiation therapy.
They then tracked the patients over time, looking for a correlation between the amount of oxygen levels in the prostate tumour relative to the muscle tissue at the time of therapy and later looked at the increase in PSA levels.
The study showed that eight of the 57 patients experienced an increase in PSA levels following prostate cancer treatment, defined as an increase of 2 ng/mL above the lowest PSA reading following brachytherapy. Overall, average muscle oxygenation was 12.5-times higher than that of the tumour.
The researchers used a statistical model that accounted for such risk factors as tumour grade, PSA level and tumour size and determined that low oxygen was a significant independent predictor of an increase in PSA levels.
Even after accounting for PSA value, Gleason score, tumour size, age, and other prostate cancer risk factors, the researchers said that low oxygen in tumour alone could predict the likelihood of increased PSA levels, and potentially cancer recurrence.
"Now, the goal is to apply the results to the clinic," Turaka said.
"We already knew that there are hypoxic (low oxygen) regions within cancers. 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 tumours with dose escalation radiation oncology strategies and targeted agents," she said.