Photodynamic Therapy

Photodynamic Therapy (PDT) uses a photosensitizing agent and light to destroy cancer cells. A photosensitizing agent is first either injected or applied to the skin. A waiting period will allow it to pass from normal cells. This period of time can be up to 48 hours and is called the drug to light interval.

Then light is sent into the tumor causing a chemical reaction with the photosensitizing agent and tissue oxygen produced by the light. The procedure takes about thirty minutes.

Photodynamic agents:

Porfimer sodium (Photofrin) is injected and utilizes a red argon laser for activation and treats some basal cell carcinomas, tumors of the vulvar, cervix and vagina, and esophageal cancer. It can be used to shrink inoperable tumors in the esophagus, and of the non-small cell lung cancer variety in the endobronchial area. Per the American Cancer Society: “The laser uses is a low-power light so it does not burn, and there is little or no pain during the procedure. The light is applied for 5 to 40 minutes, depending on the size of the tumor being treated. Any dead tissue left in the treated area is removed about 4 or 5 days later during endoscopy or bronchoscopy.”

Aminolevulinic Acid-ALA- (Luvulen) utilizes a blue light instead of the red laser light. ALA is applied to the skin and is used to treat certain pre-cancerous skin conditions. It is approved for the face and scalp. Per the American Cancer Society: “During the light therapy you may feel stinging or burning once the area is exposed to the blue light, but it should go away within a day. The treated areas may get red and scale and crust for up to 4 weeks before healing. If a lesion does not completely go away after treatment, the area can be treated again 8 weeks later. ”

Methyl ester ( Metvixia Cream) a form of Aminolevulinic Acid-ALA- that gets into the cancer cells better, and is used for non-hyperkeratotic actinic keratoses of the face and scalp with a red argon laser light. First the area is scraped and then the cream is applied and covered with a dressing for three hours. Per the American Cancer Society: “You may feel stinging or burning once the area is exposed to the light. Two treatment sessions are usually done 7 days apart. The treated area may turn red, blister, scale, and crust for up to 10 days before healing.”

Advantages of PDT:

Disadvantages of PDT:

• Photosensitivity for four to six weeks
• Argon laser only penetrates 1/3 of an inch into tissue

Resources:

National Cancer Institute: Photodynamic Therapy for Cancer: Q & A

VCU Massey Cancer Center: Photodynamic Therapy