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ProstateCancerMetastasis







Prostate cancer has been shown to metastasize by following the venous drainage system through the lower
paravertebral plexus, or Batson's plexus.4,9 Although hematogenous spread of other malignancies is most
commonly to the lungs and liver, 90 percent of prostatic metastases involve the spine, with the lumbar spine
affected three times more often than the cervical spine. Prostate cancer also spreads to the lungs in about 50
percent of patients with metastatic disease, and to the liver in about 25 percent of those with metastases.4

Epidural metastases are the result of contiguous spread from lesions of the calvaria to the meninges.
Because of the protective layer of the dura mater, subdural and intra-parenchymal metastases from prostate
cancer are rare (Figure 2).

Sites of spinal metastases from prostate cancer are illustrated in Figure 3. Metastases that lead to spinal
cord compression are usually located in the vertebral column (85 percent of cases) or the paravertebral
space (10 to 15 percent of cases).10




Sites of spinal metastases in prostate cancer: spinal cord, sub-arachnoid space,
subdural space, vertebral column, and intervertebral foramen. Leptomeningeal
carcinomatosis generally involves the subarachnoid and dural spaces, whereas
epidural metastases that lead to spinal cord compression normally extend from
lesions in the vertebral column or intervertebral foramina.

SYMPTOMS

The symptoms of spinal cord compression include progressive radicular pain that is
aggravated by movement. This pain can be confused with the pain caused by an
osteodegenerative process of the spine. However, reclining does not alleviate back
pain in patients with spinal cord compression resulting from metastatic prostate cancer.
Back pain is present in nearly all patients with prostate cancer that has metastasized
to the spine. Percussion over the involved vertebral body may evoke tenderness.

Muscle weakness evolves over a few days to weeks after the initial pain. Weakness
usually affects the proximal muscles of the lower extremities and may or may not involve
 sensory loss. Autonomic dysfunction can cause urinary retention or, less frequently, bladder
or bowel incontinence.

DIAGNOSIS

In 85 to 90 percent of patients with epidural cord compression, plain-film radiographs of the spine
detect abnormalities such as collapse or erosion of the vertebral body or pedicle, but these findings
are not specific.10 If spinal cord compression is suspected, magnetic resonance imaging (MRI) should
be performed on an emergency basis (Figure 4). If MRI is not available, computed tomographic (CT)
myelography can be used. Neuroimaging of the entire spine is necessary because epidural tumors may
develop at different levels of the spine.11





Chelated gadolinium–enhanced sagittal magnetic resonance image of the spine in a
66-year-old man who presented with urinary frequency for one week, mid-back pain,
paresthesias and weakness of the legs for two days, and a prostate-specific antigen
level of 87 ng per mL. Large, hypointensity lesions (arrows) are seen in the T4 and T5
vertebral bodies.


Cerebrospinal fluid (CSF) examination is not very helpful and is rarely required for the
diagnosis of spinal cord compression if MRI is available. CSF examination has a high
false-negative rate for the detection of malignant cells.

The serum prostate-specific antigen (PSA) level is highly predictive of bone metastasis.
If the serum PSA level is above 100 ng per mL, the positive predictive value is 74 percent.
If the serum PSA level is less than 10 ng per mL, the negative predictive value is 98 percent.12
The CSF PSA level may prove useful for identifying intradural metastasis of prostate cancer in
patients with an as yet unestablished primary tumor or with multiple malignancies. The medical
literature contains a report of a 79-year-old man with lumbosacral pain who repeatedly had
normal serum PSA levels and neuroimaging studies, but a CSF PSA level that was elevated to
29 ng per mL; MRI studies ultimately detected spinal metastasis from prostate cancer.13

TREATMENT

Treatment should be initiated as soon as spinal cord compression is diagnosed. With prompt
treatment, there is an 89 to 100 percent likelihood of preserved ambulation in patients who present
without walking difficulties. The likelihood of subsequent ambulatory function drops to 39 to 83
 percent in patients who present with impaired ambulation, and to 10 to 20 percent in those
who present with paralysis.14,15

Treatment involves reducing or alleviating pain as well as maintaining overall neurologic function.
 By using a combination of pharmaceutical and nonpharmaceutical modalities, physicians can
achieve pain control in 85 to 95 percent of patients.16 Opioid medication is the mainstay of
therapy for patients with severe, debilitating pain. Regimens using morphine, hydromorphone
(Dilaudid), fentanyl (Duragesic), and oxycodone (Roxicodone) should follow the analgesic
“ladder” developed by the World Health Organization, with rescue doses of an opioid
available to manage breakthrough pain.16,17

Intravenously administered corticosteroids help to decrease cord edema and pain, retain
motor function, and improve outcome after treatment. In one placebo-controlled study,18
corticosteroids improved ambulatory function from 63 percent to 81 percent in patients
with high-grade radiologic lesions. After six months, 59 percent of the steroid-treated
patients still ambulated, compared with 33 percent of placebo-treated patients; however,
median survival remained equal. Nonetheless, dexamethasone sodium phosphate
(Decadron) is the treatment of choice in patients with spinal cord compression
caused by metastatic prostate cancer.

The dosing of dexamethasone is somewhat controversial. Depending on the
severity of the lesion, investigators have recommended an intravenous bolus
dose (loading dose) ranging from 16 to 100 mg, followed by 4 to 24 mg given
intravenously four times daily for three days; tapering is accomplished by
reducing the dosage by one third every three days during radiotherapy.19
High-dose dexamethasone therapy with a bolus dose of 96 to 100 mg has
side effects that outweigh the benefits over use of a 16-mg loading dose
 with a 14-day taper.20,21 Furthermore, the 16-mg regimen does not have
a significant difference in the number of patients having pain, bladder
dysfunction, or inability to walk.20,21

Surgical decompression is usually reserved for patients with a solitary
spinal lesion (which is seldom the situation in metastatic prostate cancer).
In hormone-naïve patients, corticosteroids and androgen ablation therapy a
re given priority, followed by radiotherapy in patients who become refractory
to corticosteroids and hormone-deprivation therapy. At this juncture,
 a medical oncologist should be involved.

The treatment of spinal cord compression generally improves motor strength
 and function in patients with metastatic prostate cancer. However, there is
a 45 percent risk of another episode of compression at the same site or a
 new site within two years.11

http://www.aafp.org/afp/2002/0501/p1834.html

This is the largest accessory gland of the male reproductive system.
The prostate (prostate gland) is partly glandular and partly fibromuscular.
It is about the size of a walnut and surrounds the prostatic urethra.
It is enveloped in a thin, dense fibrous capsule (true capsule), which is enclosed within a loose sheath derived from the pelvic fascia called the prostatic sheath (false capsule).
It is continuous inferiorly with the superior fascia of the urogenital diaphragm.
Posteriorly, the prostatic sheath is part of the rectovesical septum.
This separates the bladder, seminal vesicles, and prostate from the rectum.
The prostatic venous plexus lies between the fibrous capsule and the prostatic sheath.
The prostate has a base, apex, and 4 surfaces (posterior, anterior, and 2 inferolateral surfaces).

The Base of the Prostate
The base of the prostate (its vesicular surface) is closely related to the neck of the urinary bladder.
The prostatic urethra enters the middle of the base near its anterior surface.

The Apex of the Prostate
The apex of the prostate is inferior and is related to the superior fascia of the urogenital diaphragm.
It rests on the sphincter urethrae muscle and is embraced by the medial margins of the levator ani muscles.

The Posterior Surface of the Prostate
This is triangular and flattened transversely.
It faces posteriorly and slightly inferiorly toward the urogenital diaphragm.
It rests on the ampulla of the rectum.
Thus, this surface can be palpated by a digit in the rectum.
Usually, the posterior surface has a shallow median groove, demarcating the lateral lobes.
The lateral lobes are often fused and clinicians often refer to them as the posterior lobe.
Superiorly on the posterior surface, there is a shallow groove where the ejaculatory ducts enter the prostate.
This groove indicates the middle lobe, the small section of the prostate between the ejaculatory ducts and the urethra.
The middle lobe lies posterior to the uvula vesica of the urinary bladder.
The prostatic utricle is located in the substance of the middle lobe.

The Anterior Surface of the Prostate
This is transversely narrow and convex and extends from the apex to the base.

The Inferolateral Surfaces of the Prostate
These meet anteriorly with the convex anterior surface and rests on the fascia covering the levator ani muscles.

The Prostatic Ductules or Ducts
There are 20 to 30 of these in number.
They open chiefly into the prostatic sinuses on each side of the urethral crest on the posterior wall of the prostatic urethra.
This occurs because most glandular tissue is located posterior and lateral to the prostatic urethra.
The prostatic secretion, a thin milky fluid, is discharged into the prostatic part of the urethra by contraction of the smooth muscle.
Prostatic fluid provides about 20% of the volume of the semen.

Arterial Supply of the Prostate
The arteries are derived mainly from the inferior vesical and middle rectal arteries.
They are branches of the internal iliac artery.

Venous Drainage of the Prostate
These for the prostatic venous plexus around the sides and base of the prostate.
This plexus is located between the capsule of the prostate and its fascial sheath.
It drains into the internal iliac veins.
It also communicates with the vesical venous plexus and the vertebral venous plexus.

Lymphatic Drainage of the Prostate
The lymph vessels terminate chiefly in the internal iliac and sacral lymph nodes.
Some vessels from its posterior surface pass with the lymph vessels of the bladder to the external iliac lymph nodes.

Innervation of the Prostate
Parasympathetic fibres arise from the pelvic splanchnic nerves (S2, S3, and S4).
The sympathetic fibres are from the inferior hypogastric plexuses.
Subpages (1): ProstateCancerIncidence
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