According to a recent article published in the International Journal of Radiation Oncology, Biology and Physics, patients with rectal cancer that has low expression of cyclooxygenase-2 (Cox-2) have a lower incidence of cancer recurrence near or at the site of origin (local recurrence) following radiation therapy. Conversely, those with high expression of Cox-2 do not appear to gain benefit in terms of local cancer recurrences with radiation therapy.
The Cox-2 enzyme (protein) is involved in inflammatory pathways in the body. Cox-2 expression has been implicated in the development and/or persistence of various types of cancer, as well as in differences in responses to certain types of therapy. It continues to be evaluated as a “marker” for prognosis in cancer as well as in individualized treatment approaches.
Rectal cancer is a disease in which malignant cells arise from the cells of the rectum. The rectum is part of the digestive system and is made up of the final 6 inches of the large intestine. Current treatments for rectal cancer include surgery, chemotherapy and radiation. Radiation therapy is used to decrease the risk of a local cancer recurrence, or to shrink the cancer prior to surgery. Chemotherapy is used to decrease the risk of a cancer recurrence anywhere in the body.
Researchers from Sweden recently conducted a clinical trial to evaluate a possible association between expression of Cox-2 and response to radiation therapy in patients with rectal cancer. This study included patients with rectal cancer who had undergone radiation therapy prior to surgery. Samples of the patient’s cancer at its original site, as well as sites to which it may have spread, such as lymph nodes, were evaluated for levels of Cox-2 expression.
Cox-2 expression was related to the risk of a local recurrence in these patients:
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• Rates of local recurrences at the site of radiation were reduced in patients with low levels of Cox-2 expression.
• Rates of local recurrences were not affected by radiation therapy in patients with high levels of Cox-2 expression.
The researchers concluded that the level of Cox-2 expression is associated with the risk of a local recurrence following radiation therapy in patients with rectal cancer. These results lend to further evidence that individualized treatment regimens are necessary to provide optimal long-term outcomes for patients with this disease. Future clinical studies are necessary to confirm this association.
Patients with rectal cancer who are to undergo radiation therapy may wish to speak with their physician regarding their individual risks and benefits of participating in a clinical trial further evaluating Cox-2 expression and prognosis, or other novel therapeutic approaches.
Two sources of information regarding ongoing clinical trials include the National Cancer Institute (cancer.gov) and www.cancerconsultants.com.
Reference: Pachkoria K, Zhang H, Adell G, et al. Significance of Cox-2 expression in rectal cancers with or without preoperative radiotherapy. International Journal of Radiation Oncology, Biology, Physics. 2005; 63: 739-744.
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