How does one best distinguish between a tumor and a trauma?
The most thorough sequence in evaluation a bone scan abnormality is:
1. do a plain x-ray or a CT scan of the area to see if there are blastic
changes in the area of the bone scan abnormality. Except for the spine, this
is the only step usually done beyond the BS.
2. Do an MRI looking for marrow changes consistent with underlying cancer.
An MRI of the spine can help to rule out spinal cord compression, a medical
emergency if present. The MRI is more sensitive for evaluating the spread of
prostate cancer to the bones than is a bone scan.
3. Perform a needle biopsy looking to confirm the presence of cancer
cells. This is seldom done since this is an invasive procedure.
In an established disease, as illustrated in the above patients bone
scan, there is no doubt about the existence and progression of the disease.
Sometimes fractures are easily distinguished from metastases. This might
be the case when there is a linear line of dark spots across the ribs where
a fall against some object might have caused rib fractures. Radiologists
always seem to hedge their analysis with words like "may", "could not be
excluded" and so forth. Here's an example radiology report and comments by
Dr. Stephen Strum on the P2P forum
http://www.ustoo.com/Prostate_Pointers.asp
Report: Bone Scan = increased activity within the anterior aspect
of the right third rib. This may simply represent a healing rib fracture,
although other etiologies including a metastatic bone lesion could not be
excluded. A small focal zone of increased activity within the upper thoracic
spine at the level of T2-T3 may simply represent focally activity
degenerative change, although other etiologies including a metastatic bone
lesion could not be excluded. A comparison x-ray of the right sided ribs and
upper thoracic spine would be helpful.
Strum:
"Here is where PLAIN x-rays of the rib and thoracic spine are of great value.
Here is the thinking (which is often completely ignored):
If the bone scan shows abnormality AND the plain film confirms that an old
fracture or degenerative joint disease (DJD) is present in that location,
then the bone scan findings MOST LIKELY do NOT relate to PC.
However, if the PLAIN X-rays do NOT explain the abnormality on the bone
scan, then this represents PC until proven otherwise.
Unfortunately, what happens 90% of the time is that the Plain film does not
show any pathologic process and yet the bone scan is NOT considered abnormal
and likely related to PC.
Report: X-ray Right ribs=Multiple views demonstrate no
fracture. No Pneumothorx. No extapleural soft tissue thickening.
Strum:
Therefore, the PLAIN RIB x-rays do not explain the uptake on the bone scan.
The rib, therefore, must be viewed with suspicion for being a site of bone
metastasis.
Report: X-ray Thoracic Spine= 2 views demonstrate extensive
Osteophyte formation. No evidence of compression fractures or subluxation.
Strum:
Therefore, the PLAIN x-rays of the thoracic spine do explain the bone scan
uptake and thus this area is NOT to be considered PC."
My PSA Decreased, my Alkaline
Phosphatase has normalized, but my Bone Metastases are Still There.
What Gives?
This was nicely addressed in a
post made by Charles Myers, MD:
Dr. Charles Myers wrote the following explanation of Bone, Bone Scan, and
Bone Mets (11 Apr 2001) in a post to the hrpca list.
"When prostate cancer invades bone, it is a response in the surrounding bone
that leads to the deposition of additional bone. This additional bone that
is deposited traps the radioactive isotope used in the bone scan, leading to
a hot spot on the bone scan. If you biopsy the bone lesion, in some patients
all you will see is a vast sea of newly formed bone with scattered prostate
cancer cells that compose less than 5-10% of the bone lesion - all the rest
are normal bone elements. In most other patients, this newly formed bone is
interspersed with areas of bone breakdown. The areas of bone breakdown are
caused by substances the cancer cells secrete that dissolve the bone. In a
rare patient, you will see only areas of bone break down.
So, the bone lesions of prostate cancer vary from patient to patient.
Some have just areas of new bone formation. Most have a mixed picture of
bone formation and breakdown. A rare patient has only bone breakdown.
There are markers of these bone events that you can see in the blood. The
one most commonly available is the alkaline phosphatase, which is commonly
elevated in men with prostate cancer invading bone. This protein is produced
by the bone, not the cancer.
With effective chemotherapy of prostate cancer, it is common to see the
PSA decline by 50-90%. It is a common experience among investigators in this
field that a decline of 50% in the PSA correlates with a significantly
longer survival. This is true regardless of the drug being used. What
happens to the bone scan and alkaline phosphatase in these responding
patients? Often the alkaline phosphatase will increase and the bone scan can
actually worsen transiently. What is going on here? The best guess is that
this represents a healing response in bone. Perhaps the areas of bone
breakdown are now healing. Over time, in patients with a particularly good
response, some bone lesions may heal. It is quite uncommon for all the bone
lesions to heal. Many patients who have an excellent response in terms of
PSA decline, pain relief and survival that is apparently prolonged will not
heal any bone lesions.
What happens with hormonal
therapy? One of the best papers on this is David Crawford's paper in the New
England Journal of Medicine at the end of the 1980s where they compared
lupron alone with lupron plus flutamide. Approximately 40% of the patients
had some resolution of bone or soft tissue masses, but less than 10% had
complete resolution of all bone lesions. Essentially the same picture as we
see with effective chemotherapy.
Why should it be so hard to find
a treatment that normalizes the bone scan? Normalization of the bone
scan would require the bone to heal. This means that all of the abnormal
bone must be cleared out and new normal bone form and mature. In men in this
age group, this process can take up to several years. This can be seen by
how long the bone scan remains abnormal after a bone fracture. In my own
case, I fell off a bike and bruised the bone over my right hip one year
before my bone scan. The area still was hot on bone scan and I had to have
additional studies to rule out bone mets. I discussed this in the April 1999
issue of the newsletter, Prostate
Forum, Volume 4 Number 4, The Physician Becomes the Patient: April
1999."
Author: Howard Hansen
Date: 2/16/07
For Further Information
The Mayo Clinic
- Bone Scan
The Prostate Cancer Research Institute's
Insights Newsletter -
an Article by O. Sartor.
Cancer
help, UK article on bone scans
The Loyola University Chicago Stritch School of Medicine has a
webpage devoted to bone metastases -- for all cancers, not just prostate
-- and diagnosic techniques.
Cancer.net (ASCO) article on Bone Scan - What to Expect -
www.cancer.net
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