PDT – Treating Cancer with Light One of the most common treatments for cancer is chemotherapy. During chemotherapy, strong drugs are used to kill cancer cells. Each drug used for chemotherapy has a potential list of side effects including pain, nausea and vomiting, blood disorders, fatigue, hair loss, and memory issues to list a few. Doctors also use radiation for cancer treatment. It is called ionizing radiation. because it forms ions (electrically charged particles) in the cells of the tissues it passes through. It creates ions by removing electrons from atoms and molecules. This can kill cells or change genes so the cells stop growing. Other forms of radiation such as radio waves, microwaves, and visible light waves are called non-ionizing. They don’t have as much energy and are not able to form ions. Like chemotherapy, radiation has debilitating side effects. One type of cancer treatment that has been developed to avoid the side effects mentioned above. It is Photodynamic therapy (PDT). Pro PDT – PDT is a treatment that uses a drug, called a photosensitizer and a particular type of light wave. When photosensitizers are exposed to a specific wavelength of light, they produce a form of oxygen that kills nearby cells. Each photosensitizer is activated by light of a specific wavelength. This wavelength determines how far the light can travel into the body. Doctors can use specific photosensitizers and wavelengths of light to treat different areas of the body with PDT. In the first step of PDT for cancer treatment, a photosensitizing drug is injected into the bloodstream. The drug is absorbed by cells all over the body but stays in cancer cells longer than it does in normal cells. Approximately 24 to 72 hours after injection, when most of the agent has left normal cells but remains in cancer cells, the tumor is exposed to light. The photosensitizer in the tumor absorbs the light and produces an active form of oxygen that destroys nearby cancer. In addition to directly killing cancer cells, PDT appears to shrink or destroy tumors in two other ways. The photosensitizer can damage blood vessels in the tumor, thereby preventing the cancer from receiving necessary nutrients. PDT also may activate the immune system to attack the tumor cells. PDT is usually used to treat tumors on or just under the skin or on the lining of internal organs or cavities such as the esophagus or lungs. PDT can be performed as an outpatient treatment. It can be repeated several times and can also be used in combination with other treatments. Con PDT – The drug commonly used in PDT, porfimer sodium, makes the skin and eyes sensitive to light for approximately 6 weeks after treatment. Patients are advised to avoid direct sunlight and bright indoor light for at least 6 weeks. Photosensitizer drugs tend to build up in tumors and the activating light is focused on the tumor. As a result, damage to healthy tissue is minimal. However, PDT can cause burns, swelling, pain, and scarring in nearby healthy tissue. Other side effects of PDT are related to the area that is treated. They can include coughing, trouble swallowing, stomach pain, painful breathing, or shortness of breath, although these side effects are usually temporary. The light needed to activate most photosensitizers cannot pass through more than about one-third of an inch of tissue (1 centimeter). For this reason, PDT is usually used to treat tumors on or just under the skin or on the lining of internal organs or cavities. PDT is also less effective in treating large tumors, because the light cannot pass far into these tumors PDT is a local treatment and generally cannot be used to treat cancer that has spread. Finally, PDT can’t be used in people who have certain blood diseases, such as any of the porphyrias (a rare group of diseases that affect the skin or nervous system) or people who are allergic to porphyrins. This allergy is rare, but it may happen in those who have gotten porphyrins in the past. Mr. Stone has several small skin cancers on his back. Based on the passage, which treatment should Mr. Stone consider and why? A) Traditional radiation because it the ionizing wavelengths will quickly kill the targeted cancer cells. B) PDT because it works well on surface cancers and causes minimal damage to surrounding tissue. C) Chemotherapy because Mr. Stone can avoid further tissue damage to his skin. D) Traditional radiation because Mr. Stone is very sensitive to sunlight.