Two new reasons to get serious about sunscreen

Answered by Brendan Curti, M.D., medical oncologist, director of the Providence Biotherapy Program at Providence Cancer Center and director of genitourinary oncology research at the Robert W. Franz Cancer Research Center in the Earle A. Chiles Research Institute.

It's a fact: Sunscreen protects you from cancer-causing UV radiation. UV is by far the leading cause of skin cancer, which is – by far – the most common type of cancer in the United States. And contrary to what you may think, all kinds of skin cancer - even the non-melanoma kinds – have the potential to kill you if they progress too far.

But if that's not enough to persuade you to put on some sunscreen, here are two new reasons to get serious about it.

1. Skin cancer increases your risk of other kinds of cancer.

The increasing rates of skin cancer in the United States suggest that even though we know how to prevent it, many of us just don't find the threat of skin cancer as scary as other cancers – at least, not scary enough to bother with sunscreen. But consider this recent finding: Once you develop skin cancer, your risk of a host of those other cancers goes up.

A study published in PLOS Medicine in 2013 found that having a non-melanoma skin cancer was "significantly associated with an 11 percent higher risk of other primary cancers (excluding melanoma) in men and a 20 percent higher risk of other primary cancers (excluding melanoma) in women."

Survivors of melanoma – the most lethal form of skin cancer – also have a heightened risk of other cancers, according to an earlier study in the Archives of Dermatology. That study found that having melanoma increased the risk of developing a second cancer by 28 percent. About 12 percent of the patients studied developed at least one additional cancer after their melanoma. One quarter of these were new melanomas. Among the rest, the most common were breast and prostate cancers and non-Hodgkin lymphoma, although the risks for multiple other types of cancer went up as well.

That bottle of sunscreen looks a lot more potent when you consider that it can protect you not just from skin cancer, but also from the increased risks of all the other cancers that could follow.

2. Sunscreen protects the genes that protect you from all kinds of cancer.

A recent Australian study found that wearing sunscreen goes beyond protecting you from skin cancer – it also shields a very important gene called "p53," which protects you from all kinds of cancer.

Found throughout your body, p53 acts like a spellchecker for your DNA. When it finds a cell with DNA damage, it calls on other genes to repair the damage. If p53 determines that the cell is too damaged to repair, it blocks the cell from dividing and forces it to self-destruct. This prevents mutated cells from growing and becoming potentially cancerous.

The p53 gene performs its tumor-suppressing repair work for all kinds of potential cancers, including skin cancer. When UV damages the DNA in your skin, p53 gets to work. But even this superhero gene has limits to how much UV it can take. Over time, repeated UV exposure can damage p53 genes, leaving them too weak and crippled to perform their vital repair work – and leaving you more susceptible to skin cancer and other cancers.

Given all that this gene does to protect you from cancer, it seems a small thing to ask to protect it with a little sunscreen.

Thanks to these studies, we now know that wearing sunscreen helps protect us not only from skin cancer, but from all kinds of cancer. So act as if your life depended on it: Grab that bottle of SPF-30 and put it to good use.

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Dr. Curti and Walter Urba, M.D., Ph.D., coauthored the chapter on Cancers of the Skin in the 2014 edition of the medical textbook Harrison's Principles of Internal Medicine, to be published soon. Dr. Urba is the director of cancer research at Providence Cancer Center.

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