phototherapy

Phototherapy

Phototherapy


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  • - KARINE RIAD
  • - M.D. CANDIDATE
  • - UNIVERSITY OF OTTAWA

DOES PHOTOTHERAPY CAUSE CANCER?

The effects of phototherapy on the risk of skin cancer have long been controversial.
But what are the different types of phototherapy?
What is it even used for?
What exactly is phototherapy?

WHAT IS PHOTOTHERAPY?

Phototherapy, also known as light therapy, is a treatment which involves exposing the skin to ultraviolet A (UVA) or ultraviolet B (UVB) rays under medical supervision. This is different than heliotherapy, where skin is exposed directly to the sun.

WHAT IS PHOTOTHERAPY USED FOR?

When using phototherapy, the UV light enters the upper layer of the skin affecting skin and nearby immune cells in ways that we don’t fully understand,” explains Dr. Litvinov, Director of Dermatology Research at McGill University. “Ultimately, and fortunately this leads to an improvement in various skin conditions such as psoriasis, eczema or vitiligo, to name a few.” Phototherapy can be done in a

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MAIN TYPES OF PHOTOTHERAPY

Psoralen-UVA (PUVA) and Narrowband UVB (NB-UVB)

NB-UVB uses a small targeted range wavelength which consists of 311nm of UVB radiation. This type of wavelength is the most effective in treating diseases, as compared to broadband UVB, and reduces exposure to the more dangerous wavelengths responsible for skin cancer and sunburns. “It is well accepted in medicine that NB-UVB is not going to cause skin cancers after long use. This is not true for Broad Band UVB machines or PUVA treatments”, explains Dr. Litvinov. “In fact, treatment with broad band UVB is in many ways similar to being exposed to the actual sun in a controlled fashion.

”PUVA on the other hand, involves treatment with a photosensitizer (psoralen) pill by mouth followed by UVA treatment or, applying topical psoralen to the skin before being exposed to the UVA radiation (320 to 400nm).

“Psoralens are compounds that make us burn in the sun much more easily. Psoralens are found in common plants such as celery and lime. For instance, we commonly see patients in our clinics who get lime on their skin while drinking a margarita on a beach leading to severe sunburn and blistering. (Please don’t try this during your next vacation.) Psoralens combined with deep penetrating UVA light can be very effective and also very dangerous. We use these medicinal properties to treat several skin diseases”, explains Dr. Litvinov.

There are many dangers of taking psoralens and exposure to sun after their ingestion can cause damage to the eyes, blistering rashes, accelerated skin aging and lead to deadly cancers such as melanoma. Therefore, PUVA treatments are always carefully supervised by a dermatologist.
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SO, DO ANY OF THEM CAUSE CANCER?

There are a few studies that have looked into this matter. As mentioned before, evidence suggests that there are no significant associations between patients who undergo NB-UVB treatment and the risk of melanoma or nonmelanoma skin cancers. However, the same can’t be said for patients who are treated with Broad Band UVB or PUVA radiation. These patients were found to have a higher incidence of nonmelanoma skin cancer and melanoma. Therefore, continuous monitoring is advised in patients who have underwent lengthy courses of PUVA radiation. “These patients have to come at least once a year for a skin check to make sure that there is no melanoma or other skin cancers,” highlights Dr. Litvinov

Ultimately, research suggests that NB-UVB phototherapy prevails as a safer treatment modality and that phototherapy in general should not be indicated in patients with a history of melanoma or nonmelanoma skin cancer.

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IMPORTANT CONSIDERATIONS – TANNING BEDS

Tanning beds and sunlight are also considered to be types of phototherapy. We’ve all heard of people turning to tanning beds to “catch some rays” during the winter to feel better. Besides, tanning beds are safer than tanning outdoors, right? Wrong. Since tanning beds mostly emit UVA light, some used to believe that it mainly caused skin aging. However, we now know that the longer wavelengths seen in UVA rays penetrate deeper into the skin and are highly associated to skin cancer, including melanoma. Just ONE tanning session significantly increases your chances by 20% of developing a cancer! So it’s not safe or recommended by a doctor as an alternative to phototherapy.

In conclusion, phototherapy is a powerful medicine that can treat many skin conditions. It is important to discuss risks and benefits with a certified dermatologist to determine the treatment that is best for you. Often the doctor will start with the safest treatment such as NB-UVB and if it does not work well in your case he or she may add a cream or a pill to help phototherapy work better. In some cases, a dermatologist may switch you to Broad Band-UVB or PUVA depending on your specific disease.