Psoriasis and the Risk of Skin Cancer
Last updated: June 2018
Having moved to a new city, I recently had to start the hunt for a new Family Doctor. Anyone living in Canada knows that this can be a long and unnecessarily arduous process, but one of my best friends worked at a clinic accepting new patients, and that’s how I met Dr. A. During my initial assessment I talked about my history with psoriasis, explaining my diagnosis, all the treatments I had cycled through, and how I was managing today. Dr. A asked “do you find that the sun helps your psoriasis? Do you wear sunscreen?” I gushed about my recent trip to the Caribbean where my skin cleared up considerably but admitted that no, I had not worn sunscreen every day because the sun is so helpful for my psoriasis. Dr. A remarked that she would put a note in my file to discuss the early warning signs of skin cancer and make this a focus at my yearly check-ups.
I had a moment of shock. Skin cancer? Was she serious? But I’m so young! I reflected after that appointment and realized that I may have an increased risk. After all, I sometimes forgo sunscreen in the summer when out for brief periods to maximize the benefit for my psoriasis, and I have been for UVB phototherapy. I also realized that I didn’t know a whole lot about the subject (I mean, does sunscreen even block the rays that help psoriasis?! Does UVB phototherapy increase my risk?). So I did some research, and here’s what I learned.
Why does the sun help?
Sunlight increases the local production of vitamin D in your skin, and vitamin D has long been known to improve psoriatic lesions. Scientists believe the mechanism of action is twofold: vitamin D slows skin cell turnover, and local vitamin D has anti-inflammatory properties. Indeed, vitamin D analogues are commonly prescribed as topicals (think Dovonex and Vectical), and can also enhance the effect of topical steroids (but oral vitamin D is not nearly as effective at reducing lesions, in case you were wondering!). In addition to vitamin D production, sunlight can actually be immunosuppressive to the skin, which may halt the autoimmune cascades that cause plaques in the first place. Lastly, being outside in the sun is relaxing for most people, and any way that we can reduce our stress is good for our skin! I’m still trying to figure out a way to get Caribbean prescriptions for “heliotherapy” from my Dermatologist (yes, that’s a real term!).
Other ways to catch some rays
The benefits of sunlight are harnessed by three additional treatments for psoriasis: UVB therapy, PUVA therapy, and excimer laser therapy. You can read more about these therapies here, but suffice it to say that they all use directed, ultraviolet rays to aid in plaque-clearing. Many psoriasis sufferers find tanning beds help their psoriasis as well. Tanning beds/booths primarily emit UVA rays, the most prevalent ray in sunlight (albeit they do so in a more concentrated way).
So, do all of these treatments increase your risk of skin cancer?
Light therapy and skin cancer
It has generally been found that UVB phototherapy does not increase your risk of skin cancer (although there may not be enough formal studies to know for sure)1 Conversely, some studies have found a very slight increase in the incidence of skin cancer for psoriasis patients treated with PUVA phototherapy2. The risk may increase if you are fair-skinned or have had multiple high dose treatments. There are no formal studies regarding excimer laser therapy, but given that it too uses UVB and only targets non-normal skin, the hypothetical incidence may be lower, as with regular UVB phototherapy. The research is far more definitive on tanning booths, which demonstrably increase your risk of skin cancer. The CDC reports that in one study, the risk of melanoma was increased by 75% for those who started tanning before the age of 35. Based on the evidence available, tanning may be the most dangerous way to catch artificial rays, and is not recommended by the NPF3.
Outside of these, is there anything else psoriasis sufferers should note? Yes! If you are receiving any type of phototherapy you should limit your natural sun exposure, as your skin will more easily be damaged (sunburns, in addition to increasing your risk of skin cancer, can also trigger the Koebner phenomenon and may lead to more active lesions). To follow that up, many medications we take as psoriasis sufferers (like methotrexate, topical steroids, psoralens, NSAIDS, etc.) can cause photosensitivity and further increase your chances of sunburn (ouch!). Be sure to check with your doctor if any of your medications may cause photosensitivity (sidebar, many other medications like certain antibiotics and blood pressure drugs can have the same effect!).
Natural sunlight and skin cancer
So most phototherapy treatments for psoriasis (except for tanning) do not appear to significantly increase your risk of skin cancer4, but we know that natural sunlight does. How can we get the benefits of the sun and reduce our risk then? From my research, most experts and professional organizations agree that while a broad spectrum sunscreen does reduce the percentage of helpful UVB rays reaching your skin, it still allows enough UVB through to have a beneficial effect, while also reducing your risk of skin cancer. You can further protect yourself by reducing your time in the sun; 30 minutes seems an adequate amount of time to realize the benefits! And of course, following both of these guidelines will reduce your risk of sunburn, which is bad for your psoriasis and increases your risk of skin cancer.
It’s important to note that not all psoriasis responds well to the sun! There are people who notice a worsening of lesions with any light exposure. If this is you, talk to your doctor, especially before starting any formal light therapy.
As a note for everyone (not just psoriasis sufferers), it’s important to regularly check your skin for any changes. For more information about the warning signs of skin cancer, check out The American Cancer Society’s fact sheet 5.
And if any of you out there find a way to convince your Dermatologist to write you a prescription for the Caribbean, make sure to share that strategy with me!
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