Photodynamic therapy

There are many different methods of treatment for cancer, including chemotherapy, radiation therapy, and photodynamic therapy (PDT). Photodynamic therapy will be focused on in this article, highlighting the basics of the treatment, what it is used for, and the benefits, side effects, and drawbacks.

What is Photodynamic Therapy?
PDT is a treatment that uses special drugs, called photosensitizing agents, and a special light to ultimately kill cancer cells. The light is needed because the drugs will not work unless they are activated by the light. The drugs are either injected into the bloodstream or applied to the skin, depending on the part of the body that is receiving the treatment. Soon enough, the drug absorbs into the cancer cells; then the light is applied to the area. The period in between when the drug is injected and when it is absorbed into the cells is called the drug-to-light interval, and can take hours to days, depending on the exact drug. The light basically causes a chemical reaction between the drug and oxygen that kills the cancer cells. Other possible avenues are that the PDT works to destroy the blood vessels supplying the cancer cells and to alert the immune system and activate an attack on them.

Types of Cancer it Kills

The most common types of cancer that PDT is used for are Barrett’s esophagus, early esophageal cancer, obstructing esophageal cancer, persistent or recurrent esophageal cancer, gastric cancer, lung cancer, and macular degeneration.

PDT Drugs
As mentioned above, the time for absorption of the drug can take several hours or several days, depending on the type of drug used. There are three different kinds of drugs.

  1. Porfimer Sodium. This is the most commonly chosen drug for PDT. It works on esophageal cancers, non small cell lung cancer, some skin cancers, and possibly tumors in the vaginal region. A red light activates it.
  2. Aminolevulinic Acid (ALA). This photosensitizing agent is put directly on the skin. For this reason, it treats cancers of the skin, or infections of the skin that could possibly become cancerous. A special blue light activates it.
  3. Methyl Ester of ALA. This is one of the many forms of ALA that have been developed and used. This one in particular enters the cancer cells very easily. Activated with a red light, it is used to treat skin conditions that can be become cancer.

Benefits of PDT

The good thing about PDT is that it has shown to successfully treat certain types of cancers and pre-cancers, as listed above. There are no long-term side effects associated with it, and it is less invasive than surgery. It is easy to target the exact area needing treatment, and it takes up a very short amount of time. Unlike radiation, if necessary, PDT can be repeated on the same site, and in any case, there is little or no scarring. Lastly, it is less costly than other cancer treatments.

Side Effects and Drawbacks of PDT
The light can’t penetrate the body too deeply, so PDT can only be used to treat tumors on or just underneath the skin or on the lining of internal organs. For this reason, PDT also can’t be used to treat cancer that is widespread throughout the body. There are also side effects. Porfimer sodium makes the eyes sensitive to light for about 6 weeks after treatment. While damage to healthy tissue is minimal, it is possible to experience swelling, burns, pain, and scarring in nearby tissue. Temporary side effects relate to the area treated, and can include coughing, trouble swallowing, stomach pain, painful breathing, or shortness of breath.

Last updated on Nov 3rd, 2010 and filed under Cancer Research. Both comments and pings are currently closed.

Comments are closed