Photodynamic therapy (PDT) is a relatively new treatment for certain types of non-melanoma skin cancer and sunspots. A photosensitising agent is applied to the treatment site for several hours prior to activation of the cream with a specialised light source. The two main types of PDT available are MetvixTM-PDT and 5-aminolevulinic acid (ALA)-PDT.
Methyl aminolevulinate (MetvixTM) photodynamic therapy (PDT) is used for specific subtypes of non-melanoma skin cancer. PDT is not suitable for treatment of melanomas or thick non-melanoma skin cancers.
MetvixTM is applied to both the skin cancer and a margin of surrounding normal skin. The site is then covered with a dressing and left for 3 hours. During this time, the MetvixTM is preferentially absorbed by the damaged skin and is much less well-absorbed by normal skin. The ointment is then wiped off and visible red light from a lamp is shone onto the area for about 8 minutes. This activates the photosensitiser and destroys the skin cancer. Two treatments one week apart are required.
The treated area and some of the surrounding skin will be red for 1 to 2 weeks. Occasionally some people develop blisters at the treatment site. There could be some increase or decrease in the pigmentation of the skin after PDT and this may or may not be permanent.
Cure rates are as follows:
- Bowen’s disease (non-invasive squamous cell carcinoma or SCC) 90-100%
- Superficial basal cell carcinoma (BCC) 80%
In the longer term, it is necessary to keep the area and the rest of the skin under regular surveillance. This is because some lesions could recur after PDT. In addition, a person who has had skin cancer is at a higher risk of developing new lesions.
5-aminolevulinic acid-PDT (ALA) is also a topical photosensitising agent. It is the first compound in the porphyrin synthesis pathway, the pathway that leads to the production of heme in red blood cells in mammals.
This treatment is used for sun damaged skin that has pre-cancerous lesions called solar keratoses (sunspots). Depending upon the degree of initial sun damage, to achieve maximum improvement, 1 – 2 treatments four weeks apart, are most effective. More treatments can be performed at periodic intervals in the future to maintain the rejuvenated appearance of the skin. Patients with severe sun damaged skin manifested by solar keratoses, texture and tone changes including mottled pigmentation and skin laxity may see good results. There may be reduced scarring and improved cosmetic outcome compared with cautery, surgery or medicated ointments. Up to an 80% initial clearance of sun spots has been demonstrated.
ALA-PDT involves a single morning. The entire area of the face is treated in one go. Only abnormal cells are targeted by the ALA and normal skin should not be affected. Both visible and pre-clinical (invisible) lesions are treated.
After the treatment it is important to stay indoors and avoid sun exposure for 72 hours. A hat, long sleeves and SPF 30+should beworn daily for at least 2 months. The treated areas will peel for about a week, with some redness of the area evident for up to a month. Temporary swelling of the lips and around the eyes can occur for a few days. Darker pigmented patches can become temporarily darker and then peel off, leaving normal skin. This usually occurs over 7-10 days.
If you have skin cancer and would like to explore photodynamic therapy as a possible treatment, be sure to ask a dermatologist about your options. Contact us today.