Lesions to be treated with PDT must be pretreated by scraping with a knife or curette to remove dead cells and fibrotic tissue as much as possible. Possible bleeding must be stopped before the cream is applied. The creams should be applied over the lesion with an occluding bandage approximately 3 hours before light therapy.
- The lesion(s) are examined by a doctor and suitable lesions are marked and drawn on a bodymap.
- Measure lesion(s)
- In certain cases, a histology or cytology specimen is taken before the treatment is initiated. The cells are scraped from the surface of the tumor with a curette or knife and the material is placed onto a slide.
- For thick tumors, some of the tumor tissue is scraped away before the cream is applied. For thinner lesions, the dead cells are scraped away from the surface.
- In some cases, the skin is punctured with a needle along the periphery of the lesion in order for the cream to be absorbed deeper into the tumor.
- The cream (Metvix®) containing light sensitive material is applied and the lesion is covered.
The patient waits for 3 hours.
- The bandage is removed and the surface cream is wiped away.
- A pad of gauze is applied over the lesion with a hole, which is slightly larger than the lesion.
- The lesion is treated for approximately 8 minutes with a lamp calibrated to deliver a dose of about 37 Joule/cm2, depending on the diameter and depth of the lesion.
- If the lesion is located in the face, the eyes are covered with small shields which are fastened with aluminum tape to exclude light. If the lesion is on the eyelid, a shield is placed underneath the eyelid after local anesthesia is applied to the eye.
This procedure may cause pain. The need for pain medication varies and depends on what area of the body is treated.
- Treatment in the face, fingers, and legs may cause greater pain than treatment on other parts of the body.
- Large lesions are often more painful to treat than smaller ones. For large lesions, local anesthesia is often administered in combination with systemic pain medication. This type of pain is difficult to treat.
- Mild pain can be alleviated by rinsing the lesion with water while irradiating, or by raising the lamp slightly away from the lesion.