STAR ABSTRACT

Radiological man-
agement of skeletal

metastases, multiple
myeloma and

lymphoma
Maximilian FReiser

MD

In malignant tumors distant
metastases are of utmost importance
for the choice among different treat-
ment options. Depending upon the
primary tumor, lung, liver and the
skeletal system are frequent sites of
distant metastases. The diagnosis of
multiple myeloma is based on labora-
tory findings. For staging of this dis-
ease, plain radiograms of the skeletal
system are obtained in order to assess
skeletal involvement and fracture risk,
especially of the spinal column.
Lymphoma usually originates from
the lymph nodes and staging is
focussed on the visualization of the
extent of lymph node involvement. In
advanced stages of malignant lym-
phoma, the skeletal system may also
be involved.

Skeletal metastases, multiple
myeloma and lymphoma are mainly
distributed via the arterial circulation
and seed into the bone marrow. As the
neoplastic cells proliferate the normal
bone marrow elements are replaced.
Due to its better vascularization, the
red marrow is more frequently affect-
ed. In advanced stages of bone mar-
row involvement, the yellow marrow

is replaced by red marrow due to the
demand in production of blood cells
(reconversion) and peripheral skeletal
elements are also prone to seeding of
metastatic cells.

Various imaging modalities are
used for the diagnostic workup of
skeletal manifestations of metastases,
multiple myeloma and lymphoma.
Their relative value depends on the
principle of the particular imaging
modality on one hand, and the bio-
logical properties of the underlying
malignancy on the other hand.

Plain radiography, CT, MRI, bone
scanning and PET are adequate meth-
ods for the diagnosis of these disor-
ders and frequently a combination of
these techniques is employed.
Recently whole body MRI, whole
body CT and CT-PET have been
described.

Radiography
In order to detect bone destruc-

tions on plain radiograms about 30%
of the bone substance has to be
removed. Cortical destructions are
more apparent than purely trabecular
lesions. In preexisting osteoporosis,
lysis of the bone is more difficult to
assess. Numerous reports have shown
that radiography is less sensitive than
bone scanning, PET, CT and MRI in

33 SA JOURNAL OF RADIOLOGY • December 2002

the detection of skeletal metastases,
multiple myeloma and lymphoma.
When neoplastic cells are invading the
bone marrow without or with minor
destruction of the bone trabecular, no
radiographic abnormalities can be
detected.

Radiography, on the other hand,
allows one to differentiate lytic, scle-
rotic and mixed pattern of bone
metastases and to establish differential
diagnoses when other imaging
modalities, e.g. bone scanning show
suspicious findings.

Computed
tomography

With single slice CT only limited
anatomical areas could be examined
and CT was used to clarify ambiguous
results obtained with other modali-
ties. Multislice CT enables one to scan
large portions of the body within
short acquisition times and with thin
collimation. Multiplanar reconstruc-
tions allow one to display the skeletal
system in imaging planes adequate for
diagnostic reading, e.g. Sagittal and
coronal MPR's of the spine and coro-
nal MPR's of the pelvis. CT is also
superior to radiography in the assess-
ment of bones at risk of fracture. In
the spine endplate fractures not visu-
alized on radiograms can be detected.
Recently it was published that MSCT
with coronal and sagittal MPR's is effi-
cient in staging patients with multiple
myeloma by demonstrating nodular
destructions and also tiny trabecular
and cortical defects. Replacement of
bone marrow by neoplastic tissue
results in an increase of density as
demonstrated by CT. This is better
recognizable within the fatty marrow
than the red marrow and does not
allow for a reliable diagnosis.



STAR ABSTRACT

Magnetic
resonance

imaging (MRI)
MR! has a unique soft tissue con-

trast and enables for the election of
diffuse and focal bone marrow infil-
tration. TI-weighted spin echo, STIR
and fat sat proton density and T2-
weighted pulse sequences are most
sensitive for the detection of neoplas-
tic infiltration of the bone marrow.
Numerous reports underline the
superior sensitivity of MR! in the
detection of skeletal metastases, and
manifestations of multiple myeloma
and lymphoma respectively. Whole
body MR! has been performed in
comparison to bone scanning in the
detection of skeletal metastases. The
total number of metastases detected
with MR! was higher than that of
bone scanning. MR! was particularly
useful in the spine and pelvis, whereas
bone scanning performed better in
the skull and ribs. In addition to skele-
tal metastases MR! was able to detect
metastases to other organs with high
accuracy.

In multiple myeloma MR! enables

one to differentiate diffuse, nodular
and mixed nodular and diffuse skele-
tal manifestations. For the assessment
of diffuse bone marrow infiltration by
myeloma, contrast enhanced MR!
proved to be very valuable.
Enhancement within the bone mar-
row of 20% and more is indicative of
moderate to high grade myeloma
infiltration. Low grade infiltration can
not be diagnosed with MR! and bone
biopsy is required. In addition to clin-
ical parameters MR! findings are an
independent prognostic factor in
patients with multiple myeloma.

Bone scanning
and PET

In bone metastases with sclerotic
or mixed pattern, bone scanning is
very sensitive, whereas purely lytic
metastases (renal cell carcinoma, thy-
roid cancer, multiple myeloma) are
frequently not associated with tracer
accumulation. While bone is highly
sensitive, its specificity is limited.
Therefore, unless findings are specific
for neoplastic infiltration, correlation
with other imaging techniques is

required. FDG- PET is correlated to
increased metabolism of tumor cells
and enables one to diagnose increased
cell turn over of neoplasms. However,
false-positives and negatives have to
be ruled out.

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34 SA JOURNAL OF RADIOLOGY • December 2002