Photodynamic Therapy

 

Photodynamic therapy (PDT) is a treatment which has been approved to treat Actinic keratosis in addition to some forms of skin cancer. There are other indications for PDT which can be discussed further with your dermatologist.

PDT is one option what enables what is called a treatment to areas of the face and scalp with substantial lesions. It acts selectively on pre-cancer cells and can even act on subclinical lesions or lesions that may not have surfaced yet. In this way, PDT is considered as a treatment for existing Actinic Keratosis and it also plays a proactive and preventative role in addressing pre-cancer lesions.

PDT uses a medication called Metvix which uses the power of light to destroy cancer cells. Light may be in one of two forms – either using daylight or the power of the sun or an in-office red-light. Talk to your dermatologist for more information regarding these two treatments.

PDT is non-invasive with very minimal downtime. Depending on the source of light you use, the treatment duration will range from 2.5-3.5 hours. You will be sun-sensitive for two days after the treatment and it would be best to remain indoors during this time.

PDT although used mainly for actinic keratosis and skin cancer, also has the benefit of reducing sun damage like sun freckles and skin redness from damaged superficial vessels. It has also been shown to help in stimulating collagen formation and help with the smoothing of fine lines and wrinkles. This leads to an overall improvement in both tone and texture of the skin.

Frequently Asked Questions

Can you tell me more about PDT?

PDT uses compounds called photosensitizing agents to selectively destroy pre-cancerous and cancerous cells of the skin. These compounds are most commonly applied topically (directly on the skin) in the Dermatology setting and once absorbed, they concentrate in pre-cancerous and cancerous cells. Metvix® (methyl aminolevulate) is one such photosensitizing agent used.

Metvix® destroys cancer cells after being activated by light, either in the form of sunlight or from a red-light used in the office. It is the combination of Metvix® and light energy that targets pre-cancerous and cancerous skin cells. Specific conditions PDT can be used to treat include actinic keratoses (pre-cancerous spots) and various skin cancers (basal cell carcinoma, squamous cell carcinoma in situ, etc), but it can also be used in the treatment other skin conditions such as psoriasis and even for cosmetic purposes.

Metvix® is not suitable for the treatment of all types of skin cancers. A detailed discussion with your dermatologist will help in deciding if this is the right treatment for you. 

It is also formulated using nut oils, so if you are allergic to peanuts or almonds you cannot be treated using Metvix®.

Should I use sunlight or red-light source in the office?

Both will work equally well to treat your skin condition. Choosing between the two will depend on the time of year, area being treated, and pain tolerance. Using sunlight to activate the Metvix® cream can only be done on non-rainy days with a temperature greater than 10°C (cloudy days are fine), which limits treatment in the winter months to in office red-light only. Using sunlight is also only approved for the treatment of lesions of the face and scalp. The downside of the red-light is many patients report it to be much more painful compared to activation with sunlight.  

How will the PDT Process Work?
  • You will receive a prescription for Metvix® (which comes as a cream you need to refrigerate) and will need to bring the medication to your appointment. The cream (which treats an area equivalent to approximately half your face) and its application cost ~$600.00, but coverage is available with many drug plans.
  • If using sunlight: A sunscreen (provided by your Dermatologist) will be applied to the areas of your skin requiring treatment. The Metvix® cream requires visible portions of the suns rays to become activated, but not the sun’s dangerous ultraviolet rays (which are blocked with the sunscreen). Prior to applying the Metvix®, your Dermatologist will gently scrape your skin to allow the medication to properly absorb. You will then sit in sunlight within 30 minutes of the cream being applied for 2-2.5 hours. Make sure to wear protective clothing and apply sunscreen to other areas of your body exposed to the sun during this time! After the treatment is complete, the cream can be washed off with water.
  • If using in office red-light: Unlike the UV rays from the sun, the red-light is not damaging to your skin. Therefore, after gently scraping the areas requiring treatment, the cream can be applied. An occlusive dressing is then applied over the cream for 3 hours and then removed. During this time, you can leave the clinic, but will need to return so the in office red-light can be used to activate the compound in your skin for 6 minutes.
What to Expect Following PDT?

The most frequent symptoms during and following treatment are painful and burning skin sensations typically beginning during treatment with light (with red-light being more severe) and lasting for a few hours with resolution on the same day. In the weeks following treatment as your skin heals, redness, swelling, blisters and ulceration will develop before completely resolving. More rarely, rashes to the cream have been described (allergic/irritant contact dermatitis).

As a general rule, Metvix® will effectively treat 80% of pre-cancerous and cancerous lesions in 80% of patients after one treatment. Depending on your specific situation, more than one treatment may be required. Your response to treatment will usually be assessed during a follow-up appointment 3-4 months after treatment.

Ngan, Vanessa. Photodynamic Therapy. DermNet New Zealand. https://www.dermnetnz.org/topics/photodynamic-therapy/. 2003. Sept 2, 2017.
Galderma. Product Information Metvix®. https://www.galderma.com.au/Portals/4/PIs%20and%20CMIs/Metvix%20cream_PI%20_140826.pdf. 2014. Sept 3, 2017.

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