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What is a laser?
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 a single wavelength and can be
focused in a very narrow beam. This makes it both powerful and precise.
Lasers can be used instead of blades (scalpels) for very careful
surgical work, such as repairing a damaged retina in the eye or cutting
through tissue.
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. Today, 3 kinds of lasers are commonly used in medicine; they are
the carbon dioxide, argon, and the Neodymium:Yttrium-Aluminum-Garnet
(Nd:YAG) lasers. They are discussed below. Some of the newer lasers
that are now being tested for use in cancer care include the
holmium:YAG, copper vapor, and diode lasers.
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
surface of the skin without going into the deeper layers.
Argon
The argon laser only goes a short distance into tissue. It is
useful in treating skin problems and in eye surgery. It is sometimes
used during tests used to look for colon cancer (colonoscopies) to
remove growths called polyps before they become cancer. It can be used
with light-sensitive drugs to treat tumors in a procedure known as
photodynamic therapy (PDT). (You can learn more about this in our
information titled Photodynamic Therapy.)
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 lasers can be used through thin flexible tubes called endoscopes
to get to hard-to-reach parts inside the body, such as the swallowing
tube (esophagus) or large intestine (colon). This light can also travel
through optical fibers, which can be bent and placed right into a tumor
to heat it up and destroy it.
The Nd:YAG is sometimes used with KTP (potassium titanyl
phosphate) crystals for some kinds of surgery.
Pros and cons of laser use in medicine
Lasers have some advantages over standard surgical tools:
- Lasers are more precise and exact than blades (scalpels).
Tissue near a cut (incision) is not affected since there is little
contact with skin or other tissue.
- The heat produced by lasers helps clean (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 mean less cutting and damage to healthy
tissues (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 costs a lot of money and is bulky compared
with the usual surgical tools used today. 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 all
of the 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 used
along 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 thin, flexible tubes called endoscopes
that allow doctors to see into certain parts of the body, such as the
bladder or stomach. The light from some lasers can be sent through an
endoscope fitted with fiber optics. This lets doctors see and work in
parts of the body that could not otherwise be reached by surgery and
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 an instrument that allows very
fine movement (a micromanipulator), 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 many kinds of cancer. In the
intestines or large bowel, lasers are used to remove colon polyps,
small growths that may become cancer. 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 swallowing
tube (esophagus) and large intestine (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 require 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 not cured) with lasers. Small tumors on the vocal cords
may be treated with lasers instead of radiation in some 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 branches of the breathing tubes (bronchi), can
be treated with a flexible, lighted tube called a 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 the things
they need to live (like oxygen and food). The laser light is passed
through a fiber optic wire and right into a tumor, where it heats up,
damaging or destroying cancer cells. LITT is sometimes used to treat
tumors in the liver.
Photodynamic therapy
In photodynamic therapy (PDT), a special drug called a
photosensitizing agent is put into the bloodstream. Over time it is
absorbed by body tissues. The drug remains in or around tumor cells for
a longer time than it does in normal tissue. Shining a certain kind of
light on the drug in the cancer cells causes a chemical reaction that
kills the cancer cells.
Photosensitizing agents are turned on or activated by a
certain wavelength of light. For example, an argon laser can be used in
PDT. When 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 when most of the agent has left healthy cells, but
is still in the 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 drug 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 used
today can leave people very sensitive to light, causing sunburn-like
reactions after only very brief sun exposure. This can greatly 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
swallowing tube (esophagus), and certain kinds of lung cancer that can
be reached with thin, flexible tubes called endoscopes. Studies are
being done 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 may work even
better.
For more information see our 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 learn to use lasers,
as the lasers themselves become smaller and cheaper, and as the
technology improves to allow tumors deep within the body to be treated,
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, 1-800-227-2345.
- 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
Provides accurate, up-to-date information on many cancer-related topics
to patients, their families, and the general public
*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 1-800-227-2345 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.
Accessed at:
http://health.enotes.com/nursing-encyclopedia/medical-lasers on June 3,
2009.
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. Accessed at:
www.cancer.gov/cancertopics/factsheet/Therapy/lasers on June 3, 2009.
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.
Last Medical Review: 06/16/2009
Last Revised: 06/16/2009
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