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FDA Approves New Treatment for Parkinson's Disease
What is Parkinson's Disease?
Parkinson's disease (PD) belongs to a group of conditions called motor system
disorders, which are the result of the loss of dopamine-producing brain cells. The four primary symptoms of PD are tremor,
or trembling in hands, arms, legs, jaw, and face; rigidity, or stiffness of the limbs and trunk; bradykinesia, or slowness
of movement; and postural instability, or impaired balance and coordination. As these symptoms become more pronounced, patients
may have difficulty walking, talking, or completing other simple tasks. PD usually affects people over the age of 50.
Early symptoms of PD are subtle and occur gradually. In some people the disease progresses more quickly than in others.
As the disease progresses, the shaking, or tremor, which affects the majority of PD patients may begin to interfere with daily
activities. Other symptoms may include depression and other emotional changes; difficulty in swallowing, chewing, and
speaking; urinary problems or constipation; skin problems; and sleep disruptions. There are currently no blood or laboratory
tests that have been proven to help in diagnosing sporadic PD. Therefore the diagnosis is based on medical history and
a neurological examination. The disease can be difficult to diagnose accurately. Doctors may sometimes request
brain scans or laboratory tests in order to rule out other diseases.
Is there any treatment?
At present, there is no cure for PD, but a variety of medications provide
dramatic relief from the symptoms. Usually, patients are given levodopa combined with carbidopa. Carbidopa delays
the conversion of levodopa into dopamine until it reaches the brain. Nerve cells can use levodopa to make dopamine and
replenish the brain's dwindling supply. Although levodopa helps at least three-quarters of parkinsonian cases, not all
symptoms respond equally to the drug. Bradykinesia and rigidity respond best, while tremor may be only marginally reduced.
Problems with balance and other symptoms may not be alleviated at all. Anticholinergics may help control tremor and
rigidity. Other drugs, such as bromocriptine, pramipexole, and ropinirole, mimic the role of dopamine in the brain,
causing the neurons to react as they would to dopamine. An antiviral drug, amantadine, also appears to reduce symptoms.
In May 2006, the FDA approved rasagiline to be used along with levodopa for patients with advanced PD or as a single-drug
treatment for early PD.
In some cases,
surgery may be appropriate if the disease doesn't respond to drugs. A therapy called deep brain stimulation (DBS) has now
been approved by the U.S. Food and Drug Administration. In DBS, electrodes are implanted into the brain and connected to a
small electrical device called a pulse generator that can be externally programmed. DBS can reduce the need for levodopa and
related drugs, which in turn decreases the involuntary movements called dyskinesias that are a common side effect of levodopa.
It also helps to alleviate fluctuations of symptoms and to reduce tremors, slowness of movements, and gait problems. DBS requires
careful programming of the stimulator device in order to work correctly.
What is the prognosis?
PD is both chronic, meaning it persists over a long period of time, and progressive,
meaning its symptoms grow worse over time. Although some people become severely disabled, others experience only minor
motor disruptions. Tremor is the major symptom for some patients, while for others tremor is only a minor complaint and other
symptoms are more troublesome. No one can predict which symptoms will affect an individual patient, and the intensity
of the symptoms also varies from person to person.
What research is being done?
The National Institute of Neurological Disorders and Stroke (NINDS) conducts PD research in laboratories at the
National Institutes of Health (NIH) and also supports additional research through grants to major medical institutions across
the country. Current research programs funded by the NINDS are using animal models to study how the disease progresses
and to develop new drug therapies. Scientists looking for the cause of PD continue to search for possible environmental factors,
such as toxins, that may trigger the disorder, and study genetic factors to determine how defective genes play a role.
Other scientists are working to develop new protective drugs that can delay, prevent, or reverse the disease.
Parkinson Society Canada is a not for profit, national charitable organization. The
Society raises money through corporate sponsorships, public donations, and planned gifts. Finding the cause and cure for Parkinson's
disease remains our chief mission. However, while we wait for answers, we must not forget the patients and caregivers. New
publications, increased patient conferences, clinical assistance programs, as well as other projects also require your support
and funding. While we have come a long way towards raising Parkinson's disease in the consciousness of Canadians, we have
more to do.
We must do more and can do more, with your help. Your support is crucial. Canadian research
into the nature and cure for Parkinson's has contributed to astounding discoveries, and for the first time researchers can
see a day when we will find the cause and cure for Parkinson's. Your commitment can make all the difference.
You can help by calling 1 800-565-3000 and asking for the Donations Department.
Parkinson Society Ottawa
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Learn about Colorectal Cancer
Colon and Rectal Cancer
The International Voice of Colon Cancer
New Drugs, Targeted Therapies
Detailed Guide: Colon and Rectum Cancer |
What's New
in Colorectal Cancer Research and Treatment? |
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Research is always under way in the area of colorectal cancer. Scientists
are looking for causes and ways to prevent colorectal cancer as well as ways to improve treatments.
Chemoprevention: Chemoprevention is the use of natural or man-made chemicals to lower a person's risk of developing
cancer. Researchers are testing whether fiber supplements, minerals (such as calcium), and vitamins (such as vitamin D), can
lower colorectal cancer risk. Some studies have found that people who take multivitamins containing folic acid (also known
as folate) have a lower colorectal cancer risk than people who do not. Recent studies have found that people who took vitamin
D supplements had a reduced rate of colorectal cancer. Increasing calcium intake by using calcium supplements or eating extra
amounts of low-fat dairy products may reduce formation of colorectal adenomatous polyps.
Although taking aspirin or some other non-steroidal anti-inflammatory
drugs (NSAIDs) is associated with a lower risk of colorectal cancer, these drugs can cause stomach ulcers and other side effects.
For this reason, taking NSAIDs specifically for this purpose is not recommended for people at average colorectal cancer risk.
You should consult with your doctor before beginning regular use of aspirin or another NSAID.
NSAIDs, such as sulindac and celecoxib (Celebrex), have been
shown to reduce formation of adenomatous polyps in people with familial adenomatous polyposis (FAP). The FDA has recently
approved celecoxib for reducing polyp formation in people with FAP. However, recent celecoxib data are now being evaluated
for a potential increased heart risk.
Studies indicate that a diet high in fruits and vegetables may
lower colorectal cancer risk, as well as the risk of several other diseases. This hasn't been completely proven by all studies.
But it is important that you eat enough servings -- at least 5 a day!
Most experts recommend that people not take large doses of vitamins,
minerals, or other agents unless they are part of a study or are under the advice and care of a doctor.
Genetics: Scientists are learning more about some of the inherited and acquired changes in DNA that cause cells of
the colon and rectum to become cancerous. Recent discoveries of inherited genes that increase a person's risk of developing
colorectal cancer are already being used in genetic tests to inform people most at risk.
Advances in understanding how these genes work are expected to
eventually lead to new drugs and gene therapies to correct these gene problems. Early phases of gene therapy trials are already
in progress. Researchers have developed ways to package DNA of normal p53 genes into a virus designed in the laboratory. Most
colorectal cancer cells have defects of this tumor suppressor gene that contribute to their abnormal growth and spread. Studies
are under way to see whether these designer viruses containing normal p53 genes can infect colorectal cancer cells and either
stop their growth or cause them to "self-destruct."
Earlier detection: Studies continue to evaluate the effectiveness of current colorectal cancer screening methods and
evaluate new approaches to informing the public about the importance of taking advantage of these methods. Less than half
of Americans age 50 or older have any colorectal cancer screening at all. If everyone were tested as recommended, tens of
thousands of lives could be saved each year. The American Cancer Society and other public health organizations are working
to increase awareness of colorectal cancer screening among the general public and health care professionals. Meanwhile, new
imaging and laboratory tests are also being developed and tested.
Virtual colonoscopy (also known as CT colonography) is a special type of CT scan that can find colorectal polyps and
cancers at least as accurately as a barium enema. This test is described in more detail in the section, "Can Colorectal Polyps and Cancer Be Found Early?" Although virtual colonoscopy is currently not included among the tests recommended by American Cancer
Society for early detection of colorectal cancer, the Society is carefully following progress in this area as technology improves
and more results become available about its accuracy.
Immunotherapy: Experimental treatments that boost the patient's immune reaction to fight colorectal cancer more effectively
are being tested in clinical trials. Some treatments use drugs like interferons and interleukins that boost the immune system
in general.
In active immunotherapy, the patient is given a vaccine that might cause the
immune system to recognize some of the abnormal chemicals in colorectal cancer cells and kill these cells. For example, the
K-ras oncogene product is altered in many colorectal cancers and researchers are testing ways to help the patient's immune
system attack cells with an altered ras protein. Researchers are also testing vaccines to direct a patient's immune system
to attack colorectal cancer cells that produce carcinoembryonic antigen (CEA). There are also studies where patients' tumor
cells are used to produce a vaccine. The vaccine is used for adjuvant therapy in the hope of preventing recurrence.
Passive immunotherapy uses antibodies made in the laboratory and then injected
into patients to seek out colorectal cancer cells that contain abnormal ras protein or other abnormal or overproduced proteins
like carcinoembryonic antigen (CEA) or the HER-2 oncogene product. Toxins or radioactive atoms can be attached to these antibodies,
so that the cell-killing chemicals or radiation is targeted specifically to the cancer cells and do not attack the healthy
cells of the body. Two antibodies, cetuximab (Erbitux) and bevacizumab (Avastin), are discussed below.
Tumor
growth factors: Researchers have discovered naturally occurring substances in the body that promote cell growth. These hormone-like
substances are called growth factors. Growth factors activate cells by attaching to growth factor receptors, which are present
on the outer surface of the cells. Some cancer cells grow especially fast because they contain more growth factor receptors
than normal cells do. One of the growth factors that has been linked to colorectal cancers is called epidermal growth factor
(EGF).
New drugs like cetuximab (Erbitux) and panitumumab (Vectibix) that specifically
kill cancer cells by attacking EGF receptors have proven effective and are now being used. More are being developed.
Another growth factor, known as vascular endothelial growth factor (VEGF),
helps tumors develop new blood vessels to get nutrients. Several drugs are now in development to try to block VEGF in order
to cut off the tumor’s blood supply. These drugs are known as antiangiogenesis drugs.
One such drug, bevacizumab (Avastin), is a monoclonal antibody that attacks
VEGF. This has proven effective also and is now being used to treat colorectal cancer. Other drugs that act against blood
vessels are being developed and tested.
Chemotherapy:
Many clinical trials are testing new chemotherapy drugs or drugs that are now used against other cancers (such as cisplatin
or gemcitabine). Other studies are looking at ways to combine drugs already known to be active against colorectal cancer,
such as irinotecan or oxaliplatin, to improve their effectiveness. Newer studies are adding cetuximab or bevacizumab to chemotherapy
as adjuvant therapy. Still other studies are testing the best ways to combine chemotherapy with radiation therapy and/or immunotherapy.
Revised: 02/22/2007
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