According to research being conducted at UC Irvine in California, two kinds of light may hold the key to a new skin cancer treatment. Currently, a specific type of photodynamic therapy (PDT) is approved by the FDA for use in lung and esophageal cancer reduction. Now, researchers are exploring ways to use a similar technique for basal cell carcinoma treatment. First, chemicals are injected into the tumor to make it highly sensitive to light. Then, the energy of the light used in the phototherapy session excites the photosensitizing agents so they create oxygen radicals. These molecules are highly reactive and can kill tissue – in this case cancer cells.

LED Imaging Used in Conjunction with Phototherapy

Besides the light used to destroy the cancer cells, doctors also need light to see what’s going on with the treatment. Light Emitting Diodes (LEDs) can be constructed to generate light in many different colors. Each color reflects differently from the skin depending on the varying characteristics of the tissue (pigmentation, structure, etc). These results can be interpreted to determine the underlying biochemistry of the tissue. The University is exploring the use of an array of 5 LED colors for advanced imaging to measure several things:

• The size, shape, and location of the tumor within the skin
• The oxygen levels in the tumorous lesion
• How the photosensitizing chemicals are distributed in the tumor
• How the light used in PDT will travel through the tissue

The goal is to use LED imaging to track the changes in the cancer cells during and after treatment. This will help researchers determine the effectiveness of phototherapy in eliminating cancer cells. The UC team has created an original device to perform the LED illumination. The process of producing the image is very quick (10 seconds or less) and the resolution is very detailed. The next step in this trial is to actually treat patients who have skin cancer. If this works, it may represent an option besides surgery for treating small cancerous lesions on the skin.

More about PDT

Besides killing cancer cells directly, photodynamic therapy is believed to damage blood vessels in the tumor and activate the immune system to attack cancer cells. There are many different wavelengths of light that can be used in PDT. Each one activates a different type of photosensitizing chemical. The decision regarding what light/chemical combination should be used is generally based on the location of the tumor. The deeper the cancer is in the tissue, the longer the wavelength of light needed to penetrate under the surface. There is a limit to how far the light beam can travel in dense tissue. Currently, only tumors close to the surface of the skin (or on the lining of various organs that can be reached using an endoscope) are treatable with PDT.

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