麻豆传媒

CHICAGO -- A year of treatment with nicotinamide, a form of vitamin B3, significantly lowered the risk for skin cancer in high-risk patients, an Australian study showed.

People who used nicotinamide had 23% fewer new nonmelanoma lesions as compared with people who did not use the agent. All 386 participants in the study had a history of skin cancer, increasing their risk for additional lesions.

The results provide the "first clear evidence that we can reduce skin cancers using a simple vitamin, together with sensible sun protection," said , of the University of Sydney.

During follow-up after the randomized phase of the trial, patients who discontinued nicotinamide lost protection soon afterward and developed new skin cancers, suggesting the need for ongoing treatment.

"Nicotinamide significantly reduced nonmelanoma skin cancer relative to placebo by 23% in just 12 months," Damian said during a press briefing that preceded the American Society of Clinical Oncology (ASCO) meeting, which begins here May 29. "Interestingly this reduction we observed seemed to start as early as the first 3 months of treatment.

"Then, when patients stopped taking the tablets, the benefit was no longer seen. In other words, you need to continue taking the tablets in order for the benefit to be sustained."

Results of the trial should not be extrapolated to other forms of vitamin B3, notably, niacin (nicotinic acid), she emphasized.

Preclinical and clinical studies suggested that nicotinamide provides energy to sun-damaged skin cells, restoring the cells' ability to, as well as innate skin immunity. In phase II studies, Damian and colleagues found that nicotinamide reduced the formation of actinic keratosis (AK) -- a malignant precursor -- and induced .

To examine the effect of nicotinamide on nonmelanoma skin cancer, investigators enrolled 386 patients who had a history of at least two skin cancers within the past 5 years. On average, the study population had eight skin cancers (and as many as 52) within the previous 5 years.

The patients were randomized to twice-daily nicotinamide or placebo and followed for 12 months. Patients had follow-up visits at 3-month intervals, and new skin cancers were excised or biopsied.

The primary endpoint was the incidence of new nonmelanoma skin cancers (basal and squamous-cell) after 12 months of randomized treatment. The key secondary endpoint was the incidence of new AK.

The results showed that the placebo-treated patients had an average skin cancer count of 2.42 versus 1.77 for the nicotinamide group, a difference that represented a 23% reduction in relative risk. Similar effects were observed for basal- and squamous-cell lesions.

Patients in the nicotinamide arm had about 15% fewer AK lesions at 12 months as with the placebo group. The study population constituted a "heavily sun-damaged group," Damian said, averaging about 50 AK lesions at enrollment, in addition to the skin cancers.

Nicotinamide does not cause side effects commonly observed with nicotinic acid, another form of vitamin B3, such has headache, flushing, and hypotension. Damian said the frequency and severity of adverse events were similar between the nicotinamide and placebo groups.

"Nicotinamide represents a new opportunity for skin cancer chemoprevention, which can be instantly translated into clinical practice," she said.

"Nicotinamide is safe, inexpensive, and widely available," she continued, and for those reasons, individuals might be tempted to self-treat or to use nicotinamide for indications other than those represented in the trial. The vitamin B3 product is for patients who have a history of skin cancer, not individuals who have never had skin cancer.

Because various forms of vitamin B3 are widely available without prescription, patients should use only nicotinamide and only after consulting with a healthcare provider. Use of nicotinamide does not obviate the need for other skin cancer prevention measures, such as use of hats, protective clothing, and sunscreens, she added.

ASCO president , of the Palo Alto Medical Foundation in California, characterized the results as "a very exciting prevention trial. We all clamor for preventing rather than treating diseases and this is a major advance for us."

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