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| Lasers In Cancer Treatment |
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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 ordinary 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 one wavelength and
can be focused in a 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. Lasers were first used
medically in 1961 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 generate the light. There are many types of lasers that
are used in medical settings, 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 relatively 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 penetrating the deeper layers.
Argon: The
argon laser penetrates only 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 along with
light-sensitive dyes to treat tumors in a procedure known as
photodynamic therapy (PDT).
Neodymium:Yttrium-Aluminum-Garnet
(Nd:YAG): Light from this laser can
penetrate deeper into tissue than light from other types of lasers, and
it can cause blood to clot quickly. Nd:YAG light can be carried 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. The erbium:yttrium aluminum garnet (Er:YAG), is being tested
for use with bladder tumors, and a diode laser called 805nID is being
tested on early stage breast cancers.
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, 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, without requiring recovery time in a
hospital.
- Healing time is often
shortened.
There are disadvantages
with laser surgery:
- Fewer surgeons are trained in
laser use.
- Laser equipment is expensive
and bulky compared to the usual surgical tools, although advances in
technology are slowly helping reduce cost and size.
- Strict safety precautions must
be observed 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.
Sometimes the laser cannot remove an entire tumor in one treatment, and
further treatments may be needed.
Treating Cancer With Lasers
Lasers were first used on skin tumors in 1961, and today one of the
most common medical uses of lasers is in cancer treatment. They can be
used in 2 ways to treat cancer:
- shrinking or destroying a
tumor with heat
- activating a chemical -- known
as a photosensitizing agent -- that destroys only the cancer cells
(photodynamic therapy)
Though lasers can be used alone, they are most often combined with
other cancer treatment methods such as chemotherapy or radiation
treatment.
Shrinking/Destroying Tumors Directly
The CO2 and Nd:YAG lasers are used to shrink or destroy tumors. They
may be used with endoscopes (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 allows doctors to 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 may be used with
low-power microscopes, giving the doctor a larger view of the site
being treated. When used with a micromanipulator (an instrument 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 and neck and the respiratory system can be treated
(but usually cannot be cured) with lasers. Treatment with lasers for
small tumors on the vocal cords may be used instead of radiation for
selected 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) uses 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 against tumors in the liver.
Photodynamic Therapy
In photodynamic therapy (PDT), a special chemical called a
photosensitizing agent
is injected into the bloodstream. It is then
allowed time to be absorbed by body tissues. The agent remains in or
around tumor cells for a longer time than it does in normal tissue. It
can then be activated by laser light to cause a reaction that kills the
cancer cells.
Photosensitizing agents are activated by a particular 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 the 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
selectively destroyed while most normal cells are spared. The damaging
effect of the photosensitizing agent occurs 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 may limit its
usefulness against deeper tumors. The photosensitizing agents now in
use can leave people very sensitive to light for a time, causing
sunburn-like reactions after very short exposures. This can severely
limit their 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 under way to find out if PDT is useful in other
cancers, such as those of the brain and prostate. Researchers also are
looking at different laser types 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 treatment of tumors deep within the body, lasers will
likely be used more often as part of cancer treatment in the future.
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.
Photodynamic Therapy
Hyperthermia
Surgery (also available in Spanish)
Understanding Chemotherapy: A Guide for Patients and Families (also
available in Spanish)
Understanding Radiation Therapy: A Guide for Patients and Families
(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
Telephone Number: 1-800-4-CANCER (1-800-422-6237)
Internet Address: www.cancer.gov
*Inclusion on this list
does not imply endorsement by the American
Cancer Society.
The American Cancer Society is happy to address almost any
cancer-related topic. If you have any more questions, please call us at
1-800-ACS-2345 at any time, 24 hours a day.
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
March 5, 2007.
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
March 2, 2007.
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;131:1236-42.
Vlastos G, Verkooijenb HM. Minimally invasive approaches for diagnosis
and treatment of early-stage breast cancer. Oncologist.
2007;12:1-10.
Revised: 4/5/07
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