The management of damage to the skin resulting from over exposure to UV-radiation and skin cancer occupies a significant proportion of our time in a Dermatology Practice. An ever increasing incidence of skin cancer and its precursor lesions, such as actinic keratosis combined with an increased awareness of the problem by the public results in a rising demand for more effective therapies. As lesions often affect the face, patients expect a practical treatment which offers good clearance, but wish for the best possible cosmetic outcome. Topical photodynamic therapy (PDT) promises to be an effective alternative to surgery and other destructive therapies in certain non-melanoma skin cancers.
Indications:
- Solar Keratosis
- Basal Cell Carcinoma (epithelioma)
- Squamous Carcinoma–in-situ (Bowens Disease)
How does PDT work?
Photodynamic Therapy is a two-step process involving the application of a topical light sensitive substance followed by activation of this substance through illumination with a proprietary light source. Commercial agents used at present are 5-Aminolevulanic Acid (ACA) and Methyl-Aminolevulinate. ALA and its esters accumulate photo active porphyrins (PAP) in neoplastic tissue. Exposure to red light in the presence of oxygen generates reactive oxygen, which damages cellular membrane, particularly in the mitochondria leading to selective cell death. Healthy surrounding tissue, which has not accumulated porphyrins, is left undamaged. After 2 to 3 weeks the lesions are replaced by new and healthy tissue. Repeat treatments are possible if required to optimize the success.
The Procedure:
Firstly scales and crusts are removed and the ALA or ALA ester is applied to all lesions plus a small surrounding area and then covered by an occlusive dressing for 3 to 4 hours. The dressing is removed, excess cream is wiped off and the area is immediately exposed to red light of 635nm with a total light dose of 80J/cm. Multiple lesions can be treated during the same treatment session.
PDT is quite a novel treatment for non-melanoma skin cancer. It is effective and has several benefits over conventional treatment approaches.
- It is as effective as surgery but superior to cryotherapy
- It is selective for cancerous tissue
- It is non-invasive and non-scarring
- It can be used repeatedly if necessary
- Cosmetic results are superior to all comparable treatments
PDT – Patient Information:
You have been prescribed PDT or Photo Dynamic Therapy – so how exactly will you be treated? PDT is a non-surgical treatment of skin cancer or pre-cancerous lesions. So you could either have Solar Keratosis or a Basal Cell Carcinoma (BCC) or Bowens Disease: it is usually red and scaly and occurs most commonly on the face, the head (in balding men) and the forearms and hands. Initially they come and go but finally they are there all the time. If left untreated, approximately 1 to 10% of those lesions turn into skin cancer per year – which is why we treat them.
A BCC or Bowen is already skin cancer and BCC’s occur most commonly on the face and back while Bowen’s is usually found on the arms and legs. Skin cancer is the most common form of cancer worldwide and in particular in our country. Almost everybody has had enough sun damage in his or her lives to develop skin cancer when we get older.
The most common treatment for solar keratosis is liquid nitrogen (freezing), while skin cancers are usually removed surgically. This obviously leads to scarring, which can be subtle if well done, but never the less as skin cancers are almost always multiple, this can be a major cosmetic problem. That is why PDT was developed in Europe. To find a treatment which is equally effective but doesn’t leave you with scars.
So how does it work?
Firstly we apply cream which is called “ALA” or Levulanic Acid, a compound related to Bilirublin and Porphyrins (substances produced in your liver). All cells in the body need this compound, but abnormal cells absorb if faster than normal cells. After we apply the cream we cover it with a Tegaderm dressing to allow it to be absorbed. After a period of 3 to 4 hours we take off the dressing and apply a light which is a visible red light. This light is not infrared or laser, just a very strong visible red light (635nm). The energy from this light activates the cream and this produces oxygen radicals. These radicals destroy all cells that have absorbed the cream, so it destroys abnormal cells but not your normal cells.
Now while those cells get destroyed and die (which is worst during the 8 to 16 minutes of treatment depending on which lamp we use) it is painful, so we give Stopayne •hour before the treatment. In the following 24 hours it will feel like very severe sunburn: the skin will turn red, sometimes swollen, some crusting and oozing can occur if the lesions were deep. In those first 24 hours it may be necessary to take more Stopayne. After that the area usually heals within 1 to 2 weeks. It is important that you keep the area well moisturized all the time (i.e. apply aqueous cream 3 to 4 times per day) and if there is oozing/ crusting apply Bactroban twice a day for 3 to 4 days. The skin will peel off (just as sun burnt skin) and heal completely. Although it will be very unsightly for those 1 to 2 weeks, the end results are always very good.
One more word regarding the pain: the pain depends on the amount of sun damage. Sometimes it is difficult to know beforehand exactly how bad it is going to be. However, it is always manageable with the Stopayne. The reddening which is seen after healing, can also take up to 6 weeks sometimes, even months to disappear. Again, this is an individual reaction but it is never permanent. The clearance or cure rate with this treatment is comparable to that of surgery but the cosmetic outcome is always better.
If you would like to know more, please do not hesitate to ask.