Lasers In Cancer Treatment

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Lasers In Cancer Treatment
Revised: 04/29/08
American Cancer Society

The term LASER stands for Light Amplification by Stimulated Emission of Radiation. Laser light is different from regular light. The light from the sun or from a light bulb has many wavelengths and spreads out in all directions. Laser light, on the other hand, has 1 wavelength and can be focused in a very narrow beam. This makes it both powerful and precise. Lasers can be used instead of scalpels for very careful surgical work, such as repairing a damaged retina in the eye or cutting through tissue.

Soon after the first working laser was developed in 1960, researchers began studying its possible uses in medicine. In 1961, lasers were first used to treat a type of skin discoloration and to repair detached retinas.

Types of lasers

Lasers are named for the liquid, gas, solid, or electronic substance that is used to create the light. Many types of lasers are used to treat medical problems, and new ones are being tested all the time. So far, 3 kinds have gained wide use in medicine:

Carbon dioxide (CO2)

The CO2 laser is mainly a surgical tool. It can cut or vaporize tissue with fairly little bleeding as the light energy changes to heat. This type of laser is used to remove thin layers from the skin's surface without going into the deeper layers.

Argon

The argon laser only goes a short distance into tissue. It is useful in dermatology and in eye surgery. It is sometimes used during colonoscopies to remove polyps. It can be used with light-sensitive drugs to treat tumors in a procedure known as photodynamic therapy (PDT).

Neodymium:Yttrium-aluminum-garnet (Nd:YAG)

Light from this laser can go deeper into tissue than light from other types of lasers, and it can cause blood to clot quickly. Nd:YAG light can be used through endoscopes to get to hard-to-reach parts of the body, such as the esophagus or colon. It can also travel through optical fibers, which can be bent and placed directly into a tumor to heat it up.

The Nd:YAG is sometimes used with KTP (potassium titanyl phosphate) crystals for some kinds of surgery. Other types of lasers that may be used in cancer care include the holmium:YAG, copper vapor, and diode lasers. Many of these lasers are being tested to treat different types of cancer.

Pros and cons of laser use in medicine

Lasers have some advantages over standard surgical tools:

* Lasers are more precise (cut more finely) than scalpels. Tissue near an incision is not affected since there is little contact with skin or other tissue.

* The heat produced by lasers helps sterilize the surgery site, reducing the risk of infection.

* Since laser heat seals blood vessels, there is less bleeding, swelling, pain, or scarring.

* Less operating time may be needed because the precision of the laser allows for a smaller incision.

* Laser surgery may be less invasive. For example, with fiber optics, laser light can be directed to parts of the body without having to make a large incision.

* More procedures may be done on an outpatient basis.

* Healing time is often shorter.

There are disadvantages with laser surgery:

* Fewer doctors and nurses are trained to use lasers

* Laser equipment is expensive and bulky compared with the usual surgical tools right now, but advances in technology are slowly helping reduce their cost and size.

* Strict safety precautions must be followed in the operating room when lasers are used. For example, the entire surgical team and the patient must wear eye protection.

* The effects of some laser treatments may not last long, so they may need to be repeated. And sometimes the laser cannot remove an entire tumor in one treatment, and more treatments may be needed.

Treating cancer with lasers

Lasers were first used on skin tumors in 1961. Today one of the most common medical uses of lasers is in cancer treatment. They can be used in 2 ways to treat cancer:

* to shrink or destroy a tumor with heat

* to activate a chemical -- known as a photosensitizing agent -- that destroys only the cancer cells (this is called photodynamic therapy or PDT)

Though lasers can be used alone, they are most often combined with other cancer treatments, such as chemotherapy or radiation.

Shrinking or destroying tumors directly

The CO2 and Nd:YAG lasers are used to shrink or destroy tumors. They can be used with endoscopes (narrow tubes that allow doctors to see into certain areas of the body, such as the bladder or stomach). The light from some lasers can be sent through a flexible endoscope fitted with fiber optics. This lets doctors see and work in parts of the body that could not otherwise be reached by surgery. It also allows for very precise aiming of the laser beam. Lasers also can be used with low-power microscopes. This gives the doctor a larger view of the area being treated. When used with a micromanipulator (an instrument used for very fine movement), laser systems can produce a cutting area as small as 200 microns in diameter -- less than the width of a very fine thread.

Lasers are used to treat several kinds of cancer. In the digestive system, lasers are used to remove colon polyps, which may become cancerous. The CO2 laser can be used to treat pre-cancerous tissue and very early cancers of the cervix, vagina, and vulva.

Lasers are also used to remove tumors blocking the esophagus and colon. Although this procedure does not cure the cancer, it relieves some symptoms, such as trouble swallowing.

The Nd:YAG laser has also been used to remove cancer that has spread to the lungs from other areas. This helps patients avoid surgery that would have required removing large sections of lung. While this type of laser cannot cure cancer, it can improve breathing and other symptoms in many patients.

Cancers of the head, neck, airways, and lungs can be treated (but usually cannot be cured) with lasers. Small tumors on the vocal cords may be treated with lasers instead of radiation in certain patients. As with tumors blocking the esophagus, tumors blocking the upper airway can be partly removed to make breathing easier. Blockages deeper in the airway, such as in the bronchi, can be treated with a flexible bronchoscope and an Nd:YAG laser.

Laser-induced interstitial thermotherapy (LITT) is based on the same idea as a cancer treatment called hyperthermia. It uses heat to help shrink tumors by damaging cells or depriving them of substances they need to live. The laser light is passed through a fiber optic and directly into a tumor, where it raises the temperature, damaging or destroying cancer cells. It is sometimes used to treat tumors in the liver.

Photodynamic therapy

In photodynamic therapy (PDT), a special drug called a photosensitizing agent is injected into the bloodstream. Over time it is absorbed by body tissues. The agent remains in or around tumor cells for a longer time than it does in normal tissue. Exposing the agent in the tumor cells to laser light causes a chemical reaction that kills the cancer cells.

Photosensitizing agents are activated by a certain wavelength of light. For example, an argon laser can be used in PDT. When treated cancer cells that contain the photosensitizing agent are exposed to red light from this laser, it causes a chemical reaction that destroys the cancer cells. Light exposure must be carefully timed so that it is used during the short period when most of the agent has left healthy cells, but remains in cancer cells.

PDT can have some advantages over other treatments. Cancer cells can be singled out and destroyed while most normal cells are spared. The damaging effect of the photosensitizing agent happens only when the substance is exposed to light, and the side effects are fairly mild.

But PDT as it is currently used is not without its problems. Argon laser light cannot pass through more than about 1 centimeter of tissue (a little more than one-third of an inch), which means it is not as useful against deeper tumors. And the photosensitizing agents now in use can leave people very sensitive to light for a time, causing sunburn-like reactions after only very brief sun exposure. This can severely limit the patient's activities until the body gets rid of the drug, which often takes weeks.

PDT is sometimes used to treat cancers and pre-cancers of the esophagus, and certain kinds of lung cancer that can be reached with endoscopes. Studies are underway to find out if PDT is useful in other cancers, such as those of the brain and prostate. Researchers also are looking at different kinds of lasers and at new photosensitizer drugs that will make it more effective.

For more information see the American Cancer Society document, Photodynamic Therapy.

The outlook for lasers in cancer treatment

Because of their power and precision, lasers are well-suited for certain cancer surgeries, and doctors are trying to find new and better ways to use them. As more cancer surgeons become trained in laser use, the lasers themselves become smaller and cheaper, and the technology improves to allow tumors deep within the body to be treated. In the future lasers will probably be used more often as part of cancer treatment.

References

Brown S, Brown EA, Walker I. The present and future role of photodynamic therapy in cancer treatment. Lancet Oncol. 2004;5:497-508.

Encyclopedia of Nursing and Allied Health. Medical Lasers. Available at: http://health.enotes.com/nursing-encyclopedia/medical-lasers. Accessed April 3, 2008.

Fried NM. Therapeutic applications of lasers in urology: an update. Expert Rev Med Devices. 2006;3:81-94.

National Cancer Institute. Lasers in Cancer Treatment: Questions and Answers. Available at: http://www.cancer.gov/cancertopics/factsheet/Therapy/lasers. Accessed April 3, 2008.

Rolle A, Pereszlenyi A, Koch R, et al. Is surgery for multiple lung metastases reasonable? A total of 328 consecutive patients with multiple-laser metastasectomies with a new 1318-nm Nd:YAG laser. J Thorac Cardiovasc Surg. 2006;131:1236-1242.

Vlastos G, Verkooijenb HM. Minimally invasive approaches for diagnosis and treatment of early-stage breast cancer. Oncologist. 2007;12:1-10.

Copyright 2009 © American Cancer Society, Inc.