Results from these studies led to the initiation of the current trial in humans. The authors stress that identifying COX-2 inhibitors and other therapies that may prevent the incidence of skin cancer does not mean that sunscreen and other protective measures should not be used to reduce the likelihood of skin cancer. It is possible that future preventive measures will include a combination of sunscreens as well as COX inhibitors or other protective therapies.
Overall, cancer caused by sunlight accounts for about half the cancer cases diagnosed in the United States. Between 1977-1978 and 1998-1999 in the Southwestern United States, the incidence of basal cell and squamous cell carcinoma increased by 50 percent and 90 percent respectively in men, and by 22 percent and 110 percent re
The study was a double-blind, multicenter, placebo-controlled trial that included 240 patients between 37 and 87 years of age. Participants in the study were at high risk for the development of non-melanoma skin cancers and exhibited pre-cancerous actinic keratoses, or scaly patches on the skin that can result from excess time in the sun.
Half of the participants were given 200 mg of celecoxib twice a day and the other half were given a placebo for nine months. They were evaluated at three, six and nine months, and again at 11 months, for the existence of new actinic keratoses, basal cell carcinomas and squamous cell carcinomas.
The participants that received the celecoxib saw significant reductions in both cancers – 68% in basal cell carcinomas and 58% in squamous cell carcinomas. These decreases are even higher than provided by the use of sunscreen, which provides only moderate protection against squamous cell and basal cell carcinomas.
“For individuals who are at very high risk of skin cancer, this may be a method to reduce the number of new tumors they develop, despite the drug’s known side effects,” said Alice Pentland, M.D., study author and chair of the Department of Dermatology at the University of Rochester Medical Center.
COX-2 inhibitors have been linked to increased risk for cardiovascular and gastrointestinal side effects. In this study, however, the researchers did not observe a significant difference between the 2 groups in cardiovascular events, such as heart attack or chest pain, or in gastrointestinal disease.
The most common side effects in this study were gastrointestinal disorders and infections. Also, previous studies have shown that serious cardiovascular events typically do not occur with COX-2 inhibitors until they have been taken for more than a year.
The researchers believe there are several possible mechanisms by which COX-2 inhibitors might slow or stop the progression of pre-cancerous cells to full-fledged tumors. COX-2 inhibitors may have an effect on the ability of non-melanoma skin cancers to grow and thrive. They may also suppress or weaken the cancer’s ability to invade surrounding tissue and spread from the initial site to other parts of the body. Finally, this class of drugs may have an anti-inflammatory effect on skin cancer development.
The results of the study were published in the Journal of the National Cancer Institute. In addition to the University of Rochester Medical Center, the University of Alabama at Birmingham, the Veteran Affairs Medical Center, Birmingham, the University of Wisconsin, Madison, the University of Michigan, the University of California, Irvine, the Washington University School of Medicine, and the University of Texas M.D. Anderson Cancer Center participated in the study.