Researchers say an over-expression of COX-2 in men with prostate cancer is associated with an increase in PSA after radiation treatment and the spread of the cancer outside of the prostate. That is the result of the first study linking COX-2 (cyclooxygenase-2) with prostate cancer radiation treatment outcomes. The study, sponsored by the Radiation Therapy Oncology Group (RTOG 92-02), was presented today at the 48th Annual Meeting of the American Society for Therapeutic Radiology and Oncology in Philadelphia by Li-Yan Khor, M.D., a fellow in the Radiation Oncology Department at Fox Chase Cancer Center in Philadelphia.
"We found that an increased level of COX-2 prior to treatment was linked with biochemical failure and distant metastasis but was not predictive of overall survival," explained Khor.
For the study, Khor and colleagues analyzed 586 cases from RTOG 92-02 which had available tissue and suitable staining by immunohistochemistry. Median follow-up was 106.9 months. The intensity of COX-2 staining was quantified by automated image analysis provided by a commercial company.
The 5 year distant metastasis rate was 10.6 percent for a COX-2 intensity score less than 134, versus 14.1 percent for an intensity score greater than 134. A high intensity of COX-2 also predicted biochemical failure, the immediate PSA rise after treatment.
Khor added that data from animals have shown that inhibition of COX-2 suppresses angiogenesis (development of blood vessels) and the growth of prostate cancer, and is believed to make the cancer cells more sensitive to radiation therapy.
"This research suggest the need to know more about the levels of COX-2 in our patients," says Khor. "If men show increased levels of COX-2 perhaps radiation treatment will follow an attempt to inhibit COX-2 expression thereby making their cancer more responsive to radiation therapy."
Khor adds "Future studies in this area should include additional biopsy information to determine if COX-2 over-expression is associated with the inability to completely eliminate the cancer within the prostate."
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