Prostate Cancer
Prostate
cancer
Prostate
cancer is a disease in which cancer develops in the prostate,
a gland in the male reproductive system. Cancer occurs when
cells of the prostate mutate and begin to multiply out of
control. These cells may spread (metastasize) from the prostate
to other parts of the body, especially the bones and lymph
nodes. Prostate cancer may cause pain, difficulty in urinating,
erectile dysfunction and other symptoms.
Rates
of prostate cancer vary widely across the world. It is least
common in South and East Asia, more common in Europe - though
the rates vary widely between countries - and most common
in the United States [1]. According to the American Cancer
Society, prostate cancer is least common among Asian men
and most common amongst Black men. with figures for European
men in between [2] [3]. However, these high rates may be
affected by increasing rates of detection [4].
Prostate
cancer develops most frequently in men over fifty. This
cancer can only occur in men; the prostate is exclusively
of the male reproductive tract. It is the second most common
type of cancer in men in the United States, where it is
responsible for more male deaths than any other cancer except
lung cancer. However, many men who develop prostate cancer
never have symptoms, undergo no therapy, and eventually
die of other causes. Many factors, including genetics and
diet, have been implicated in the development of prostate
cancer, but as of 2006, it is not a preventable disease.
Prostate
cancer is most often discovered by physical examination
or by screening blood tests, such as the PSA (prostate specific
antigen) test. There is some current concern about the accuracy
of the PSA test and its usefulness. Suspected prostate cancer
is typically confirmed by removing a piece of the prostate
(biopsy) and examining it under a microscope. Further tests,
such as X-rays and bone scans, may be performed to determine
whether prostate cancer has spread.
Prostate
cancer can be treated with surgery, radiation therapy, hormone
therapy, occasionally chemotherapy, or some combination
of these. The age and underlying health of the man as well
as the extent of spread, appearance under the microscope,
and response of the cancer to initial treatment are important
in determining the outcome of the disease. Since prostate
cancer is a disease of older men, many will die of other
causes before the prostate cancer can spread or cause symptoms.
This makes treatment selection difficult.[1] The decision
whether or not to treat localized prostate cancer (a tumor
that is contained within the prostate) with curative intent
is a patient trade-off between the expected beneficial and
harmful effects in terms of patient survival and quality
of life.
The
prostate
Main article: prostate
The
prostate is a male reproductive organ which helps make and
store seminal fluid. In adult men a typical prostate is
about three centimeters long and weighs about twenty grams.[2]
It is located in the pelvis, under the urinary bladder and
in front of the rectum. The prostate surrounds part of the
urethra, the tube that carries urine from the bladder during
urination and semen during ejaculation.[3] Because of its
location, prostate diseases often affect urination, ejaculation,
or defecation. The prostate contains many small glands which
make about twenty percent of the fluid comprising semen.[4]
In prostate cancer the cells of these prostate glands mutate
into cancer cells. The prostate glands require male hormones,
known as androgens, to work properly. Androgens include
testosterone, which is made in the testes; dehydroepiandrosterone,
made in the adrenal glands; and dihydrotestosterone, made
in the prostate itself. Androgens are also responsible for
secondary sex characteristics such as facial hair and increased
muscle mass.
[edit]
Symptoms
Early
prostate cancer usually causes no symptoms. Often it is
diagnosed during the workup for an elevated PSA noticed
during a routine checkup. Sometimes, however, prostate cancer
does cause symptoms, often similar to those of diseases
such as benign prostatic hypertrophy. These include frequent
urination, increased urination at night, difficulty starting
and maintaining a steady stream of urine, blood in the urine,
and painful urination. Prostate cancer may also cause problems
with sexual function, such as difficulty achieving erection
or painful ejaculation.[5]
Advanced
prostate cancer may cause additional symptoms as the disease
spreads to other parts of the body. The most common symptom
is bone pain, often in the vertebrae (bones of the spine),
pelvis or ribs, from cancer which has spread to these bones.
Prostate cancer in the spine can also compress the spinal
cord, causing leg weakness and urinary and fecal incontinence.[6]
[edit]
Pathophysiology
When normal cells are damaged beyond repair, they are eliminated
by apoptosis. Cancer cells avoid apoptosis and continue
to multiply in an unregulated manner.
Enlarge
When normal cells are damaged beyond repair, they are eliminated
by apoptosis. Cancer cells avoid apoptosis and continue
to multiply in an unregulated manner.
Prostate
cancer is classified as an adenocarcinoma, or glandular
cancer, that begins when normal semen-secreting prostate
gland cells mutate into cancer cells. The region of prostate
gland where the adenocarcinoma is most common is the peripheral
zone. Initially, small clumps of cancer cells remain confined
to otherwise normal prostate glands, a condition known as
carcinoma in situ or prostatic intraepithelial neoplasia
(PIN). Although there is no proof that PIN is a cancer precursor,
it is closely associated with cancer. Over time these cancer
cells begin to multiply and spread to the surrounding prostate
tissue (the stroma) forming a tumor. Eventually, the tumor
may grow large enough to invade nearby organs such as the
seminal vesicles or the rectum, or the tumor cells may develop
the ability to travel in the bloodstream and lymphatic system.
Prostate cancer is considered a malignant tumor because
it is a mass of cells which can invade other parts of the
body. This invasion of other organs is called metastasis.
Prostate cancer most commonly metastasizes to the bones,
lymph nodes, rectum, and bladder.
[edit]
Epidemiology
The
specific causes of prostate cancer remain unknown.[7] A
man's risk of developing prostate cancer is related to his
age, genetics, race, diet, lifestyle, medications, and other
factors. The primary risk factor is age. Prostate cancer
is uncommon in men less than 45, but becomes more common
with advancing age. The average age at the time of diagnosis
is 70.[8] However, many men never know they have prostate
cancer. Autopsy studies of Chinese, German, Israeli, Jamaican,
Swedish, and Ugandan men who died of other causes have found
prostate cancer in thirty percent of men in their 50s, and
in eighty percent of men in their 70s.[9] In the year 2005
in the United States, there were an estimated 230,000 new
cases of prostate cancer and 30,000 deaths due to prostate
cancer.[10]
A
man's genetic background contributes to his risk of developing
prostate cancer. This is suggested by an increased incidence
of prostate cancer found in certain racial groups, in identical
twins of men with prostate cancer, and in men with certain
genes. In the United States, prostate cancer more commonly
affects black men than white or Hispanic men, and is also
more deadly in black men.[11] Men who have a brother or
father with prostate cancer have twice the usual risk of
developing prostate cancer.[12] Studies of twins in Scandinavia
suggest that forty percent of prostate cancer risk can be
explained by inherited factors.[13] However, no single gene
is responsible for prostate cancer; many different genes
have been implicated. Two genes (BRCA1 and BRCA2) that are
important risk factors for ovarian cancer and breast cancer
in women have also been implicated in prostate cancer.[14]
Dietary
amounts of certain foods, vitamins, and minerals can contribute
to prostate cancer risk. Men with higher serum levels of
the short-chain ?-3 fatty acid linolenic acid have higher
rates of prostate cancer. However the same series of studies
showed that men with elevated levels of long-chain ?-3 (EPA
and DHA) had lowered incidence.[15] Other dietary factors
that may increase prostate cancer risk include low intake
of vitamin E (Vitamin E is found in green, leafy vegetables),
lycopene (found in tomatoes) omega-3 fatty acids (found
in fatty fishes like salmon), and the mineral selenium.
Lower blood levels of vitamin D also may increase the risk
of developing prostate cancer. This may be linked to lower
exposure to ultraviolet (UV) light, since UV light exposure
can increase vitamin D in the body.[16]
There
are also some links between prostate cancer and medications,
medical procedures, and medical conditions. Daily use of
anti-inflammatory medicines such as aspirin, ibuprofen,
or naproxen may decrease prostate cancer risk.[17] Use of
the cholesterol-lowering drugs known as the statins may
also decrease prostate cancer risk.[18] Sterilization by
vasectomy may increase the risk of prostate cancer, though
there are conflicting data.[19] More frequent ejaculation
also may decrease a man's risk of prostate cancer. One study
showed that men who ejaculated five times a week in their
20s had a decreased rate of prostate cancer.[20] Infection
or inflammation of the prostate (prostatitis) may increase
the chance for prostate cancer. In particular, infection
with the sexually transmitted infections chlamydia, gonorrhea,
and syphilis seem to increase risk.[21] Finally, obesity[22]
and elevated blood levels of testosterone[23] may increase
the risk for prostate cancer.
[edit]
Screening
Main article: Prostate cancer screening
Prostate
cancer screening is an attempt to find unsuspected cancers.
Screening tests may lead to more specific follow-up tests
such as a biopsy, where small pieces of the prostate are
removed for closer study. As of 2006 prostate cancer screening
options include the digital rectal exam and the prostate
specific antigen (PSA) blood test. Screening for prostate
cancer is controversial because it is not clear if the benefits
of screening outweigh the risks of follow-up diagnostic
tests and cancer treatments.
Prostate
cancer is a slow-growing cancer, very common among older
men. In fact, most prostate cancers never grow to the point
where they cause symptoms, and most men with prostate cancer
die of other causes before prostate cancer impacts their
lives. The PSA screening test may detect these small cancers
that would never become life threatening. Doing the PSA
test in these men may lead to overdiagnosis, including additional
testing and treatment. Follow-up tests, such as prostate
biopsy, may cause pain, bleeding and infection. Prostate
cancer treatments may cause urinary incontinence and erectile
dysfunction. Therefore, it is essential that the risks and
benefits of diagnostic procedures and treatment be carefully
considered before PSA screening.
Prostate
cancer screening generally begins after age fifty, but may
be offered earlier in black men or men with a strong family
history of prostate cancer.[24] Although there is no officially
recommended cutoff, many health care providers stop monitoring
PSA in men who are older than 75 years old because of concern
that prostate cancer therapy may do more harm than good
as age progresses and life expectancy decreases.
[edit]
Digital
rectal examination
Digital
rectal examination (DRE) is a procedure where the examiner
inserts a gloved, lubricated finger into the rectum to check
the size, shape, and texture of the prostate. Areas which
are irregular, hard or lumpy need further evaluation, since
they may contain cancer. The DRE only evaluates the back
of the prostate, but fortunately, 85% of prostate cancers
arise in this part of the prostate. Prostate cancer which
can be felt on DRE is generally more advanced.[25] The use
of DRE has never been shown to prevent prostate cancer deaths
when used as the only screening test.[26]
[edit]
Prostate
specific antigen
The
PSA test measures the blood level of prostate-specific antigen,
an enzyme produced by the prostate. Specifically, PSA is
a serine protease similar to kallikrein. Its normal function
is to liquify gelatinous semen after ejaculation, allowing
spermatazoa to more easily "swim" through the
uterine cervix.
PSA
levels under 4 ng/mL (nanograms per milliliter) are generally
considered normal, while levels over 4 ng/mL are considered
abnormal (although in men over 65 levels up to 6.5 ng/mL
may be acceptable, depending upon each laboratory's reference
ranges). PSA levels between 4 and 10 ng/mL indicate a risk
of prostate cancer higher than normal, but the risk does
not seem to rise within this six-point range. When the PSA
level is above 10 ng/mL, the association with cancer becomes
stronger. However, PSA is not a perfect test. Some men with
prostate cancer do not have an elevated PSA, and most men
with an elevated PSA do not have prostate cancer.
PSA
levels can change for many reasons other than cancer. Two
common causes of high PSA levels are enlargement of the
prostate (benign prostatic hypertrophy (BPH)) and infection
in the prostate (prostatitis). PSA levels are lowered in
men who use medications used to treat BPH or baldness. These
medications, finasteride (marketed as Proscar or Propecia)
and dutasteride (marketed as Avodart), may decrease the
PSA levels by 50% or more.
Several
other ways of evaluating the PSA have been developed to
avoid the shortcomings of simple PSA screening. The use
of age-specific reference ranges improves the sensitivity
and specificity of the test. The rate of rise of the PSA
over time, called the PSA velocity, has been used to evaluate
men with PSA levels between 4 and 10 ng/ml, but as of 2006,
it has not proven to be an effective screening test.[27]
Comparing the PSA level with the size of the prostate, as
measured by ultrasound or magnetic resonance imaging, has
also been studied. This comparison, called PSA density,
is both costly and, as of 2006, has not proven to be an
effective screening test.[28] PSA in the blood may either
be free or bound to other proteins. Measuring the amount
of PSA which is free or bound may provide additional screening
information, but as of 2006, questions regarding the usefulness
of these measurements limit their widespread use.[29][30]
[edit]
Confirming
the diagnosis
Normal prostate (A) and prostate cancer (B). In prostate
cancer, the regular glands of the normal prostate are replaced
by irregular glands and clumps of cells, as seen in these
pictures taken through a microscope.
Enlarge
Normal prostate (A) and prostate cancer (B). In prostate
cancer, the regular glands of the normal prostate are replaced
by irregular glands and clumps of cells, as seen in these
pictures taken through a microscope.
When
a man has symptoms of prostate cancer, or a screening test
indicates an increased risk for cancer, more invasive evaluation
is offered. The only test which can fully confirm the diagnosis
of prostate cancer is a biopsy, the removal of small pieces
of the prostate for microscopic examination. However, prior
to a biopsy, several other tools may be used to gather more
information about the prostate and the urinary tract. Cystoscopy
shows the urinary tract from inside the bladder, using a
thin, flexible camera tube inserted down the urethra. Transrectal
ultrasonography creates a picture of the prostate using
sound waves from a probe in the rectum.
If
cancer is suspected, a biopsy is offered. During a biopsy
a urologist obtains tissue samples from the prostate via
the rectum. A biopsy gun inserts and removes special hollow-core
needles (usually three to six on each side of the prostate)
in less than a second. The tissue samples are then examined
under a microscope to determine whether cancer cells are
present, and to evaluate the microscopic features (or Gleason
score) of any cancer found. Prostate biopsies are routinely
done on an outpatient basis and rarely require hospitalization.
Fifty-five percent of men report discomfort during prostate
biopsy.[31]
[edit]
Staging
Main article: Prostate cancer staging
An
important part of evaluating prostate cancer is determining
the stage, or how far the cancer has spread. Knowing the
stage helps define prognosis and is useful when selecting
therapies. The most common system is the four-stage TNM
system (abbreviated from Tumor/Nodes/Metastases). Its components
include the size of the tumor, the number of involved lymph
nodes, and the presence of any other metastases.
The
most important distinction made by any staging system is
whether or not the cancer is still confined to the prostate.
In the TNM system, clinical T1 and T2 cancers are found
only in the prostate, while T3 and T4 cancers have spread
elsewhere. Several tests can be used to look for evidence
of spread. These include computed tomography to evaluate
spread within the pelvis, bone scans to look for spread
to the bones, and endorectal coil magnetic resonance imaging
to closely evaluate the prostatic capsule and the seminal
vesicles.
After
a prostate biopsy, a pathologist looks at the samples under
a microscope. If cancer is present, the pathologist reports
the grade of the tumor. The grade tells how much the tumor
tissue differs from normal prostate tissue and suggests
how fast the tumor is likely to grow. The Gleason system
is used to grade prostate tumors from 2 to 10, where a Gleason
score of 10 indicates the most abnormalities. The pathologist
assigns a number from 1 to 5 for the most common pattern
observed under the microscope, then does the same for the
second most common pattern. The sum of these two numbers
is the Gleason score. The Whitmore-Jewett stage is another
method sometimes used. Proper grading of the tumor is critical,
since the grade of the tumor is one of the major factors
used to determine the treatment recommendation.
[edit]
Treatment
Treatment
for prostate cancer may involve watchful waiting, surgery,
radiation therapy, High Intensity Focused Ultrasound (HIFU),
chemotherapy, cryosurgery, hormonal therapy, or some combination.
Which option is best depends on the stage of the disease,
the Gleason score, and the PSA level. Other important factors
are the man's age, his general health, and his feelings
about potential treatments and their possible side effects.
Because all treatments can have significant side effects,
such as erectile dysfunction and urinary incontinence, treatment
discussions often focus on balancing the goals of therapy
with the risks of lifestyle alterations.
If
the cancer has spread beyond the prostate, treatment options
significantly change, so most doctors who treat prostate
cancer use a variety of nomograms to predict the probability
of spread. Treatment by watchful waiting, HIFU, radiation
therapy, cryosurgery, and surgery are generally offered
to men whose cancer remains within the prostate. Hormonal
therapy and chemotherapy are often reserved for disease
which has spread beyond the prostate. However, there are
exceptions: radiation therapy may be used for some advanced
tumors, and hormonal therapy is used for some early stage
tumors. Cryotherapy, hormonal therapy, and chemotherapy
may also be offered if initial treatment fails and the cancer
progresses.
[edit]
Watchful
waiting
Watchful
waiting, also called "active surveillance," refers
to observation and regular monitoring without invasive treatment.
Watchful waiting is often used when an early stage, slow-growing
prostate cancer is found in an older man. Watchful waiting
may also be suggested when the risks of surgery, radiation
therapy, or hormonal therapy outweigh the possible benefits.
Other treatments can be started if symptoms develop, or
if there are signs that the cancer growth is accelerating.
Most men who choose watchful waiting for early stage tumors
eventually have signs of tumor progression, and they may
need to begin treatment within three years.[32] Although
men who choose watchful waiting avoid the risks of surgery
and radiation, the risk of metastasis (spread of the cancer)
may be increased. Additional health problems that develop
with advancing age during the observation period can also
make it harder to undergo surgery and radiation therapy.
[edit]
Surgery
Surgical
removal of the prostate, or prostatectomy, is a common treatment
either for early stage prostate cancer, or for cancer which
has failed to respond to radiation therapy. The most common
type is radical retropubic prostatectomy, when the surgeon
removes the prostate through an abdominal incision. Another
type is radical perineal prostatectomy, when the surgeon
removes the prostate through an incision in the perineum,
the skin between the scrotum and anus. Prostatectomy can
cure about seventy percent of cases of prostate cancer.
Radical
prostatectomy is highly effective for tumors which have
not spread beyond the prostate. However, it may cause nerve
damage that significantly alters the quality of life of
the prostate cancer survivor. The most common serious complications
are loss of urinary control and impotence. As many as forty
percent of men will be left with some urinary incontinence,
usually in the form of leakage when they sneeze, cough or
laugh. Impotence is also a common problem. Although penile
sensation and the ability to achieve orgasm usually remain
intact, erection and ejaculation are often impaired. Medications
such as sildenafil (Viagra), tadalafil (Cialis), or vardenafil
(Levitra) may restore some degree of potency. In some men
with smaller cancers, a more limited "nerve-sparing"
technique may help avoid urinary incontinence and impotence.[33]
Radical
prostatectomy has traditionally been used alone when the
cancer is small. However, courses of hormone therapy prior
to surgery may increase cure rates and are currently being
studied.[34] Surgery may also be offered when a cancer is
not responding to radiation therapy. However, because radiation
therapy causes tissue changes, prostatectomy after radiation
has a higher risk of complications.
Transurethral
resection of the prostate, commonly called a "TURP,"
is a surgical procedure performed when the tube from the
bladder to the penis (urethra) is blocked by prostate enlargement.
TURP is generally for benign disease and is not meant as
definitive treatment for prostate cancer. During a TURP,
a small tube (cystoscope) is placed into the penis and the
blocking prostate is cut away.
In
metastatic disease, where cancer has spread beyond the prostate,
removal of the testicles (called orchiectomy) may be done
to decrease testosterone levels and control cancer growth.
(See hormonal therapy, below).
[edit]
Radiation
therapy
Brachytherapy for prostate cancer is administered using
"seeds," small radioactive rods implanted directly
into the tumor.
Enlarge
Brachytherapy for prostate cancer is administered using
"seeds," small radioactive rods implanted directly
into the tumor.
Radiation
therapy, also known as radiotherapy, uses X-rays to kill
prostate cancer cells. X-rays are a type of ionizing radiation
that can damage or destroy the DNA crucial to cancer cell
growth. Two different kinds of radiation therapy are used
in prostate cancer treatment: external beam radiation therapy
and brachytherapy.
External
beam radiation therapy uses a linear accelerator to produce
high-energy X-rays which are directed in a beam towards
the prostate. A technique called Intensity Modulated Radiation
Therapy (IMRT) may be used to adjust the radiation beam
to conform with the shape of the tumor, allowing higher
doses to be given to the prostate and seminal vesicles with
less damage to the bladder and rectum. External beam radiation
therapy is generally given over several weeks, with daily
visits to a radiation therapy center.
External beam radiation therapy for prostate cancer is delivered
by a linear accelerator, such as this one.
Enlarge
External beam radiation therapy for prostate cancer is delivered
by a linear accelerator, such as this one.
Brachytherapy
involves the placement of about 100 small "seeds"
containing radioactive material (such as iodine-125 or palladium-103)
with a needle through the skin of the perineum directly
into the tumor. These seeds emit lower-energy X-rays which
are only able to travel a short distance. Brachytherapy
seeds will stay in the prostate permanently, but men with
implanted seeds are not at risk of exposing others to radiation.[35]
Radiation
therapy is commonly used in prostate cancer treatment. It
may be used instead of surgery for early cancers, and it
may also be used in advanced stages of prostate cancer to
treat painful bone metastases. Radiation treatments also
can be combined with hormonal therapy for intermediate risk
disease, when radiation therapy alone is less likely to
cure the cancer. Some radiation oncologists combine external
beam radiation and brachytherapy for intermediate to high
risk situations. One study found that the combination of
six months of androgen suppresive therapy combined with
external beam radiation had improved survival compared to
radiation alone in patients with localized prostate cancer.[36]
Others use a "triple modality" combination of
external beam radiation therapy, brachytherapy, and hormonal
therapy.
Less
common applications for radiotherapy are when cancer is
compressing the spinal cord, or sometimes after surgery,
such as when cancer is found in the seminal vesicles, in
the lymph nodes, outside the prostate capsule, or at the
margins of the biopsy.
Radiation
therapy is often offered to men whose medical problems make
surgery more risky. Radiation therapy appears to cure small
tumors that are confined to the prostate just about as well
as surgery. However, as of 2006 some issues remain unresolved,
such as whether radiation should be given to the rest of
the pelvis, how much the absorbed dose should be, and whether
hormonal therapy should be given at the same time.
Side
effects of radiation therapy might occur after a few weeks
into treatment. Both types of radiation therapy may cause
diarrhea and rectal bleeding due to radiation proctitis,
as well as urinary incontinence and impotence. Symptoms
tend to improve over time.[37] Men who have undergone external
beam radiation therapy will have a higher risk of later
developing colon cancer and bladder cancer.[38]
[edit]
Cryosurgery
Cryosurgery
is another method of treating prostate cancer. It is less
invasive than radical prostatectomy, and general anesthesia
is less commonly used. Under ultrasound guidance, metal
rods are inserted through the skin of the perineum into
the prostate. Liquid nitrogen is used to cool the rods,
freezing the surrounding tissue at -196 °C (-320 °F).
As the water within the prostate cells freezes, the cells
die. The urethra is protected from freezing by a catheter
filled with warm liquid. Cryosurgery generally causes fewer
problems with urinary control than other treatments, but
impotence occurs up to ninety percent of the time. When
used as the initial treatment for prostate cancer, cryosurgery
is not as effective as surgery or radiation.[39] However,
cryosurgery is potentially better than radical prostatectomy
for recurrent cancer following radiation therapy.
[edit]
Hormonal
therapy
Hormonal therapy in prostate cancer. Diagram shows the different
organs (purple text), hormones (black text and arrows),
and treatments (red text and arrows) important in hormonal
therapy.
Enlarge
Hormonal therapy in prostate cancer. Diagram shows the different
organs (purple text), hormones (black text and arrows),
and treatments (red text and arrows) important in hormonal
therapy.
Hormonal
therapy uses medications or surgery to block prostate cancer
cells from getting dihydrotestosterone (DHT), a hormone
produced in the prostate and required for the growth and
spread of most prostate cancer cells. Blocking DHT often
causes prostate cancer to stop growing and even shrink.
However, hormonal therapy rarely cures prostate cancer because
cancers which initially respond to hormonal therapy typically
become resistant after one to two years. Hormonal therapy
is therefore usually used when cancer has spread from the
prostate. It may also be given to certain men undergoing
radiation therapy or surgery to help prevent return of their
cancer.[40]
Hormonal
therapy for prostate cancer targets the pathways the body
uses to produce DHT. A feedback loop involving the testicles,
the hypothalamus, and the pituitary, adrenal, and prostate
glands controls the blood levels of DHT. First, low blood
levels of DHT stimulate the hypothalamus to produce gonadotropin
releasing hormone (GnRH). GnRH then stimulates the pituitary
gland to produce luteinizing hormone (LH), and LH stimulates
the testicles to produce testosterone. Finally, testosterone
from the testicles and dehydroepiandrosterone from the adrenal
glands stimulate the prostate to produce more DHT. Hormonal
therapy can decrease levels of DHT by interrupting this
pathway at any point.
There
are several forms of hormonal therapy:
* Orchiectomy is surgery to remove the testicles. Because
the testicles make most of the body's testosterone, after
orchiectomy testosterone levels drop. Now the prostate not
only lacks the testosterone stimulus to produce DHT, but
also it does not have enough testosterone to transform into
DHT.
* Antiandrogens are medications such as flutamide, bicalutamide,
nilutamide, and cyproterone acetate which directly block
the actions of testosterone and DHT within prostate cancer
cells.
* Medications which block the production of adrenal androgens
such as DHEA include ketoconazole and aminoglutethimide.
Because the adrenal glands only make about 5% of the body's
androgens, these medications are generally used only in
combination with other methods that can block the 95% of
androgens made by the testicles. These combined methods
are called total androgen blockade (TAB). TAB can also be
achieved using antiandrogens.
* GnRH action can be interrupted in one of two ways. GnRH
antagonists suppress the production of GnRH directly, while
GnRH agonists suppress GnRH through the process of downregulation
after an initial stimulation effect. Abarelix is an example
of a GnRH antagonist, while the GnRH agonists include leuprolide,
goserelin, triptorelin, and buserelin. Initially, these
medications increase the production of LH. However, because
the constant supply of the medication does not match the
body's natural production rhythm, production of both LH
and GnRH decreases after a few weeks.[41]
As
of 2006 the most successful hormonal treatments are orchiectomy
and GnRH agonists. Despite their higher cost, GnRH agonists
are often chosen over orchiectomy for cosmetic and emotional
reasons. Eventually, total androgen blockade may prove to
be better than orchiectomy or GnRH agonists used alone.
Each
treatment has disadvantages which limit its use in certain
circumstances. Although orchiectomy is a low-risk surgery,
the psychological impact of removing the testicles can be
significant. The loss of testosterone also causes hot flashes,
weight gain, loss of libido, enlargement of the breasts
(gynecomastia), impotence and osteoporosis. GnRH agonists
eventually cause the same side effects as orchiectomy but
may cause worse symptoms at the beginning of treatment.
When GnRH agonists are first used, testosterone surges can
lead to increased bone pain from metastatic cancer, so antiandrogens
or abarelix are often added to blunt these side effects.
Estrogens are not commonly used because they increase the
risk for cardiovascular disease and blood clots. The antiandrogens
do not generally cause impotence and usually cause less
loss of bone and muscle mass. Ketoconazole can cause liver
damage with prolonged use, and aminoglutethimide can cause
skin rashes.
[edit]
Palliative
care
Palliative
care for advanced stage prostate cancer focuses on extending
life and relieving the symptoms of metastatic disease. Chemotherapy
may be offered to slow disease progression and postpone
symptoms. The most commonly used regimen combines the chemotherapeutic
drug docetaxel with a corticosteroid such as prednisone.[42]
Bisphosphonates such as zoledronic acid have been shown
to delay skeletal complications such as fractures or the
need for radiation therapy in patients with hormone-refractory
metastatic prostate cancer.[43]
Bone
pain due to metastatic disease is treated with opioid pain
relievers such as morphine and oxycodone. External beam
radiation therapy directed at bone metastases may provide
pain relief. Injections of certain radioisotopes, such as
strontium-89, phosphorus-32, or samarium-153, also target
bone metastases and may help relieve pain.
[edit]
Prognosis
Prostate
cancer rates are higher and prognosis poorer in Western
societies than the rest of the world. Many of the risk factors
for prostate cancer are more prevalent in the Western world,
including longer life expectancy and diets high in animal
fats. Also, where there is more access to screening programs,
there is a higher detection rate. Prostate cancer is the
ninth most common cancer in the world, but is the number
one non-skin cancer in United States men. Prostate cancer
affected eighteen percent of American men and caused death
in three percent in 2005.[44] In Japan, death from prostate
cancer was one-fifth to one-half the rates in the United
States and Europe in the 1990s.[45] In India in the 1990s,
half of the people with prostate cancer confined to the
prostate died within ten years.[46] African-American men
have 50-60 times more prostate cancer and prostate cancer
deaths than men in Shanghai, China.[47] In Nigeria, two
percent of men develop prostate cancer and 64% of them are
dead after two years.[48]
In
patients who undergo treatment, the most important clinical
prognostic indicators of disease outcome are stage, pre-therapy
PSA level and Gleason score. In general, the higher the
grade and the stage, the poorer the prognosis. Nomograms
can be used to calculate the estimated risk of the individual
patient. The predictions are based on the experience of
large groups of patients suffering from cancers at various
stages.[49]
[edit]
Prevention
Prostate
cancer risk can be decreased by modifying known risk factors
for prostate cancer, such as decreasing intake of animal
fat.[50] Several medications and vitamins may also help
prevent prostate cancer. Two dietary supplements, vitamin
E and selenium, may help prevent prostate cancer when taken
daily. Estrogens from soybeans and other plant sources (called
phytoestrogens) may also help prevent prostate cancer.[51]
The selective estrogen receptor modulator drug toremifene
has shown promise in early trials.[52][53] Two medications
which block the conversion of testosterone to dihydrotestosterone,
finasteride[54] and dutasteride[55], have also shown some
promise. As of 2006 the use of these medications for primary
prevention is still in the testing phase, and they are not
widely used for this purpose.
A
2003 study [5] indicated that regular ejaculations may help
prevent prostate cancer.
Angstrom Minerals Product And Price List
The information on this page has been extracted from http://en.wikipedia.org/wiki/Prostate_cancer
