Lasers in Cancer Treatment

[RandyW]

Lasers in Cancer Treatment

Posted on September 25, 2006

by Richard Johnson

The term "laser" stands for light amplification by stimulated emission ofradiation. Ordinary light, such as that from a light bulb, has manywavelengths and spreads in all directions. Laser light, on the other hand,has a specific wavelength. It is focused in a narrow beam and creates avery high-intensity light. This powerful beam of light may be used to cutthrough steel or to shape diamonds. Because lasers can focus veryaccurately on tiny areas, they can also be used for very precise surgicalwork or for cutting through tissue (in place of a scalpel).

Laser therapy uses high-intensity light to treat cancer and otherillnesses. Lasers can be used to shrink or destroy tumors. Lasers are mostcommonly used to treat superficial cancers (cancers on the surface of thebody or the lining of internal organs) such as basal cell skin cancer andthe very early stages of some cancers, such as cervical, penile, vaginal,vulvar, and non-small cell lung cancer.

Lasers also may be used to relieve certain symptoms of cancer, such asbleeding or obstruction. For example, lasers can be used to shrink ordestroy a tumor that is blocking a patient's trachea (windpipe) oresophagus. Lasers also can be used to remove colon polyps or tumors thatare blocking the colon or stomach.

Laser therapy can be used alone, but most often it is combined with othertreatments, such as surgery, chemotherapy, or radiation therapy. Inaddition, lasers can seal nerve endings to reduce pain after surgery andseal lymph vessels to reduce swelling and limit the spread of tumor cells.

Laser therapy is often given through a flexible endoscope (a thin, lightedtube used to look at tissues inside the body). The endoscope is fitted withoptical fibers (thin fibers that transmit light). It is inserted through anopening in the body, such as the mouth, nose, anus, or vagina. Laser lightis then precisely aimed to cut or destroy a tumor.

Laser-induced interstitial thermotherapy (LITT) (or interstitial laserphotocoagulation) also uses lasers to treat some cancers. LITT is similarto a cancer treatment called hyperthermia, which uses heat to shrink tumorsby damaging or killing cancer cells. (More information about hyperthermiais available in the National Cancer Institute (NCI) fact sheet Hyperthermiain Cancer Treatment: Questions and Answers, which can be found athttp://www.cancer.gov/cancertopics/fa ... perthermia on theInternet.) During LITT, an optical fiber is inserted into a tumor. Laserlight at the tip of the fiber raises the temperature of the tumor cells anddamages or destroys them. LITT is sometimes used to shrink tumors in the liver.

Photodynamic therapy (PDT) is another type of cancer treatment that useslasers. In PDT, a certain drug, called a photosensitizer orphotosensitizing agent, is injected into a patient and absorbed by cellsall over the patient's body. After a couple of days, the agent is foundmostly in cancer cells. Laser light is then used to activate the agent anddestroy cancer cells. Because the photosensitizer makes the skin and eyessensitive to light for approximately 6 weeks, patients are advised to avoiddirect sunlight and bright indoor light during that time. (More informationabout PDT is available in the NCI fact sheet Photodynamic Therapy forCancer: Questions and Answers, which can be found athttp://www.cancer.gov/cancertopics/fa ... otodynamic on theInternet.)

Three types of lasers are used to treat cancer: carbon dioxide (CO2)lasers, argon lasers, and neodymium:yttrium-aluminum-garnet (Nd:YAG)lasers. Each of these can shrink or destroy tumors and can be used withendoscopes. CO2 and argon lasers can cut the skin's surface without goinginto deeper layers. Thus, they can be used to remove superficial cancers,such as skin cancer. In contrast, the Nd:YAG laser is more commonly appliedthrough an endoscope to treat internal organs, such as the uterus,esophagus, and colon. Nd:YAG laser light can also travel through opticalfibers into specific areas of the body during LITT. Argon lasers are oftenused to activate the drugs used in PDT.

Lasers are more precise than standard surgical tools (scalpels), so they doless damage to normal tissues. As a result, patients usually have lesspain, bleeding, swelling, and scarring. With laser therapy, operations areusually shorter. In fact, laser therapy can often be done on an outpatientbasis. It takes less time for patients to heal after laser surgery, andthey are less likely to get infections. Patients should consult with theirhealth care provider about whether laser therapy is appropriate for them.

Laser therapy also has several limitations. Surgeons must have specializedtraining before they can do laser therapy, and strict safety precautionsmust be followed. Also, laser therapy is expensive and requires bulkyequipment. In addition, the effects of laser therapy may not last long, sodoctors may have to repeat the treatment for a patient to get the full benefit.

In clinical trials (research studies), doctors are using lasers to treatcancers of the brain and prostate, among others.