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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.
Additional resources
More information from your American Cancer
Society
We have selected some related information that may also be
helpful to you. These materials may be viewed on our Web site or
ordered from our toll-free number, 1-800-ACS-2345.
- Surgery
(also available in Spanish)
National organizations and Web sites*
In addition to the American Cancer Society, other sources of
patient information and support include:
National Cancer Institute
Toll-free Number: 1-800-4-CANCER (1-800-422-6237)
Web site: www.cancer.gov
*Inclusion on this list does not imply endorsement by the
American Cancer Society.
No matter who you are, we can help. Contact us anytime, day or
night, for cancer-related information and support. Call us at 1-800-ACS-2345 or
visit www.cancer.org.
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.
Revised: 04/29/08
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