Co-investigator Dr. Martin A. Weinstock of Brown University in Providence, Rhode Island, presented the study findings here Sunday at the 65th annual meeting of the American Academy of Dermatology.

Nearly 75,000 deaths between 1969 and 2000 are attributed to non-melanoma skin cancers, according to the US National Center for Health Statistics and the Centers for Disease Control and Prevention databases, Dr. Weinstock announced.

Thirty thousand of those are attributed to genital non-melanoma skin cancers, of which 22,000 occurred in women and 8,000 occurred in men.

The incidence of fatal genital non-melanoma skin cancer increases with age. For women younger than 65 years old, there are 0.8 deaths per 100,000; women between 65 and 74 years of age have a mortality of 1.8 deaths per 100,000; for those between 75 and 84 years, the mortality is 4.1 deaths per 100,000 women; and for those 85 years of age or older, the mortality increases to 8.8 deaths per 100,000 women.

In contrast, in men younger than 65 years of age, there are 0.50 deaths per 100,000 from genital non-melanoma skin cancer. That number jumps to 1.0 deaths per 100,000 during the next decade of life, rising to 1.9 deaths per 100,000 between 75 and 84. For those older than 85, the mortality from genital non-melanoma skin cancer is 4.1 deaths per 100,000.

These are skin cancers that are not caused by sun damage, Dr. Weinstock pointed out. He added that while the incidence is increasing among older individuals, it has been decreasing overall in recent years.

“There has been a 47% decline among blacks and a 30% decline among whites,” he told meeting attendees. “The decline among blacks has been quite precipitous in recent years.”

The number of deaths attributed to genital non-melanoma skin cancer was higher than Dr. Weinstock’s team expected, and he believes HPV was the major cause of those cancers. Other causes he cited included smoking, chronic inflammatory conditions, immunosuppression, lower socioeconomic status, obesity and the lack of an early circumcision for men.

The HPV vaccine “offers the potential for a substantial reduction in the development of these cancers,” the Brown University researcher noted. “Prevention and early detection are the key” for continuing the downward trend.

Non-melanoma skin cancer is the most common form of cancer in the United States, with more than 1 million cases diagnosed each year, according to the American Cancer Society. Most cases are caused by overexposure to the sun’s ultraviolet (UV) radiation. People with lightly pigmented skin and those who have previously developed skin cancer have the greatest risk of developing the condition. Non-melanoma skin cancer is curable if it is identified early, through a biopsy, and then removed through one of several methods.

The OSU researchers noted that previous studies have associated brown algae chemicals called polyphenols with cancer-fighting and antioxidant properties. The scientists used nine groups of mice, each containing 20 hairless mice that were susceptible to skin cancer caused by ultraviolet B (UVB) radiation.

Two groups received topical applications of brown algae containing either 3 milligrams (mg) or 6 mg in a mild solvent. Two other groups were fed a diet containing the algae compound in 0.1 percent or 0.5 percent concentrations. One group of control mice received no treatment but was exposed to UVB radiation.

Two groups of mice were given a standard diet with some getting UVB exposure and some without exposure. Another set of two groups received the topical brown algae applied to their skin with and without UVB exposure.

All of the treatments were administered over a two-week period followed by 24 weeks of UVB exposure. Researchers then assessed skin tumor growth and size in all mice.

They found that those exposed to UVB had an average of 8.5 tumors. Those who ingested the lower and higher doses of algae averaged only 4.7 and 3.7 tumors, respectively. The mice given the lower and higher doses of topical solvents developed 3.4 and 4.6 tumors, respectively.

Tumors were also smaller (by some 27 to 43 percent) on both sets of mice receiving brown algae compared to those that did not receive treatment.

“These compounds seemed to be dramatically effective at fairly low doses both orally and topically,” OSU principal investigator Gary D. Stoner said in a press release. “These findings suggest that, even when eaten, these compounds get to skin cells and neutralize the cancer-causing oxygen radicals that are produced by UV exposure.”

Funding for the OSU study was provided by the U.S. Department of Agriculture and the Korean Research Foundation.