Professor Diona Damian and Professor Gary Halliday, University of Sydney
More than 60% of Australians develop skin cancer during their lifetimes – it is six times more common than all other forms of cancer combined. The vast majority of skin cancers rarely spread throughout the body, but if left untreated, they can cause extensive tissue destruction. Although they are less deadly than many other cancers, non-melanoma skin cancers are by far Australia’s most expensive cancer, with costs predicted to rise to more than $700 million by 2015.
Sun exposure is the biggest risk factor for skin cancer: 90% of non-melanoma skin cancer and 65% of melanomas can be traced back to exposure to ultraviolet (UV) radiation from the sun. UV radiation causes cancer by damaging the genes of skin cells and by suppressing the immune system, which normally protects against skin cancer.
Professor Diona Damian and Professor Gary Halliday, from the University of Sydney, have made a remarkable discovery that could change skin cancer prevention worldwide. Both UVB (the type of light that is usually associated with sunburn) and UVA suppress the immune system when they hit the skin. This is important because the immune system is a big part of the body’s defence against cancer. Unusual cells, or cells that are growing incorrectly, are often targeted by the immune system and destroyed before they can develop into actual cancers. If the immune system is weakened, it means that the damage caused by sunlight isn’t repaired as quickly and is more likely to cause cancer.
Vitamin B3 is protective because it replenishes cellular energy, helping cells to repair the damage caused to their DNA by sun exposure. This means that vitamin B3 could both protect against new skin cancers and also help heal existing sun damage. For example, actinic keratoses are pre‑cancerous lesions, normally appearing on chronically sun-exposed skin as red, scaling areas. If left untreated, many progress into non-melanoma skin cancer. The researchers found that applying vitamin B3 to the skin of people with these lesions accelerated their regression within a few months. They also found that simply taking a vitamin B3 supplement twice daily reduced the number of keratoses by 35% compared to people taking a placebo.
But perhaps the biggest benefit from this discovery is the fact that vitamin B3 actually seemed to prevent new skin cancers (see Figure p.11). Of the patients taking a placebo, 32% developed a new skin cancer within 4 months. Of those taking the vitamin, only 8% did. Overall, there was an 80% reduction in numbers of new skin cancers in patients taking vitamin B3 in these Phase II studies. This substantial fall in cancers, thanks to a readily available vitamin, could dramatically change the number of people diagnosed with non‑melanoma skin cancer in Australia every year. The researchers are suggesting including it in sunscreen, especially because it helps to fight the adverse effects of UVA, which is less effectively blocked by normal sunscreen.
The researchers have also found a number of other uses for vitamin B3. It helps to prevent the immunosuppressive effects of photodynamic therapy, which is often used for skin cancer treatment. This could boost cure rates after this therapy. It also reduces DNA damage after arsenic exposure, and could work to fight arsenic‑induced skin cancer. This is a major problem, affecting millions of people in areas like Bangladesh and West Bengal, where there are high levels of arsenic in the groundwater.
The most exciting aspects of this research may be yet to come. Comprehensive testing of the effects of vitamin B3 on skin cancers is ongoing. Professor Damian is working to complete a Phase III trial of its effects in preventing non‑melanoma skin cancer in 400 people at high risk of developing it. This trial is currently in the final stages of recruitment, with more than 300 participants enrolled to date. This multicentre study will provide enough evidence to show whether the vitamin should be recommended for all people at high risk of skin cancer. Until the Phase III trial is complete vitamin B3 is not recommended for the prevention of skin cancer.
Preliminary results of this research have also shown that vitamin B3 may help to prevent melanoma, by helping melanocytes in the skin to repair their DNA more efficiently after UV exposure. This could potentially greatly improve the number of lives saved, as melanoma is by far the most deadly of the skin cancer types. If the non-melanoma skin cancer trial is successful, the next step will be the development of a clinical trial to test whether vitamin B3 can also prevent melanoma.