Cyclooxygenase 2 (COX-2) has been associated with non-melanoma skin cancers. These malignancies include basal cell carcinoma and squamous cell carcinoma, and together they make up the most common cancer type in the United States. The annual cost of treatment is an estimated $1.4 billion. Sunscreens, shade, and protective clothing offer some reduction in risk, but more preventive efforts are needed. Since COX-2 inhibitor drugs are readily available, researchers at the University of Alabama tested this option for cancer prevention.
There are two forms of the cyclooxygenase molecule, called COX-1 and COX-2. Most non-steroidal anti-inflammatory drugs such as aspirin, ibuprofen, and naproxen inhibit both COX-1 and COX-2. There is a class of drugs called coxibs that selectively inhibit only COX-2. The brand names are Celebrex, Bextra, and Vioxx. The latter two have been removed from the market because of their association with heart attacks and strokes. Celebrex (generic name celecoxib) is still on the market and used to treat arthritis. The authors of Reference 1 chose this one at a dose of 200 mg twice daily, which is the usual dose for arthritis.
The participants in the study were chosen to have 10 to 40 actinic keratoses at the time of enrollment. These are pre-cancerous skin lesions that put the subjects at high risk for nonmelanoma skin cancer. The trial was a randomized, placebo-controlled, double-blind study of 240 subjects aged 37 to 87 years. All took either celecoxib or a placebo for nine months.
Participants taking celecoxib had fewer skin cancers than those on placebo, with the difference observed as early as three months into the program. The last observation was conducted 11 months after randomization, and by this time the average number of tumors per patient was three times as high in the placebo group as in the celecoxib group (0.35 tumors per subject versus 0.14 tumors per subject).
Long-term use of celecoxib is a risk factor for cardiovascular illness. The authors suggested more research into safer ways to inhibit the COX-2 enzyme in pre-cancerous skin conditions.