Photodynamic Therapy

Photodynamic therapy is based on the idea that when both normal cells and cancer cells are treated with photosensitizing drugs, they will respond differently. This type of therapy utilizes the energy of light to kill cancer cells while leaving the healthy cells undamaged.

During a treatment with photodynamic therapy, photosensitizer drugs are given to cancer patients. This makes the cells become light sensitive. The cells that have been treated with the drug are subjected to light with a certain wavelength, which triggers them to create a particular toxic form of oxygen that destroys any cancer cells that are nearby.

About Photodynamic Therapy

In this type of treatment, the photosensitizing drug is given to the patient intravenously. It takes between 24 and 72 hours for the drug to spread throughout the bloodstream and become absorbed by the cells. Cancer cells absorb this drug more quickly than healthy cells and it stays in the cancer cells longer than it does in normal cells. Because of this, the drug is much more predominant in cancer cells when it is time for the next phase of the treatment.

The next phase of treatment is to treat the patient with a light that has a predetermined wavelength. This light reacts to the photosensitizing drug that is now present in the cancer cells. This treatment phase is as simple as shining a beam of light on the affected area for as little as a few minutes or up to an hour. When the cancer cells absorb this light, they produce a form of oxygen that is extremely reactive and gets into the cancer cells that are close by and causes damage to them. This damage eventually ends up killing those cells. This type of therapy also damages blood vessels inside of tumors. This keeps the cancer cells from being able to absorb nutrients.

Side Effects

One side effect of photodynamic therapy is that some of the drugs that are used can cause the eyes and skin to be extremely sensitive to light. This sensitivity can last up to six weeks after the treatment. The skin and eyes must be protected during this time or else they could blister or burn even with a small amount of exposure to bright lights indoors or in sunlight.

In some cases these treatments can cause burns, pain, scarring, or swelling in healthy tissue near the treated area, but this damage is normally minimal since treatment is specific to certain areas on the body. There may be other side effects like shortness of breath, coughing, painful breathing, difficulty swallowing, or stomach pain. Side effects depend on the location of the cancer being treated.

Advancements in Photodynamic Therapy

The light used for photodynamic therapy is unable to penetrate deep into the skin and is its best use is for skin cancers or certain forms of lung cancer that are close to the surface of the skin. This type of treatment may not be right for patients with particularly large tumors since the light likely would not be able to completely penetrate the tumor.

Current research on this type of therapy is attempting to expand the range of cancers that it can treat. Scientists are also hoping to make it more effective for use on large tumors. Other areas of research are looking into administering photodynamic therapy through surgery or by using fiber optics sent into the tumor itself.  While results are mixed in the use of photodynamic therapy to treat mesothelioma, especially in its advanced stages, at least one study with a six-year follow-up has found that it is helpful in treating stage I and stage II pleural mesothelioma when used immediately following surgery.