Metastatic tumors are cancers that started in another location and spread
to the bones. More than 90% of all these metastatic lesions in bone
are caused by a small number of primary tumors all of which are listed
below. Patients with metastatic bone tumors do not need to lose hope,
because new treatments and new hope is available. One new technique is
the aggressive removal of the metastatic lesions for maximum functional
restoration. (more) Make sure
you or your loved one is receiving the most thorough care appropriate
for the bone tumor problem they have.
is the third most common site of metastatic disease. Cancers
most likely to metastasize to bone include breast,
lung, prostate, thyroid
and kidney. Carcinomas are much more likely
to metastasize to bone than sarcomas. The axial skeleton is seeded more
than the appendicular skeleton, partly due to the persistence of red bone
marrow in the former. The ribs, pelvis and spine are normally the
first bones involved and distal bones are rarely affected. Metastases
are established when a single tumor cell or a clump of cells gain access
to the blood stream, reach the bone marrow through blood vessels in Haversian
canals, extravasate, multiply and neovascularize. Batson's vertebral venous
plexus allows cells to enter the vertebral circulation without first passing
through the lungs. The sluggish blood flow in this plexus is more conducive
to tumor survival, accounting for the high rate of prostate cancer metastasis
to the spine.
Pain, pathological fractures and hypercalcemia are the major sources of
morbidity with bone metastasis. Pain is the most common symptom found
in 70% of patients with bone metastases. l Pain is caused by stretching
of the periosteum by the tumor as well as nerve stimulation in the endosteum.
Pathological fractures are most common in breast cancer due to the lytic
nature of the lesions. They are uncommon in lung cancer due to short life
span and rare in prostate cancer which tend to be osteoblastic lesions.
Hypercalcemia only occurs in 10% of patients.2
Lytic bone metastases must be greater than 1 cm and have destroyed 30-50%
of the bone density 3 in order to be seen by x-ray. It is also difficult
to distinguish between metastases and benign lesions such as Paget's disease
or osteoporosis on plain film. On bone scan, radiolabeled bisphosphonates
are taken up by in areas of bone formation but not by the tumor cells.
CT is more specific than bone scan and can distinguish between osteolytic
and osteoblastic lesions. MRI is the most sensitive method of detection
bone metastases because cells can spotted before local bone reaction has
Metastatic bone lesions can be described as osteolytic, osteoblastic and
mixed. The osteolytic lesions are most common where the destructive processes
outstrip the laying down of new bone. New treatments with medicines that
may block bone lysis by tumor cells are currently in clinical trials.
Osteoblastic lesions result from new bone growth that is stimulated by
the tumor. Microscopically, most lesions are mixed.
Treatment for bone metastasis is normally palliative. An assessment of
the risk of pathological fracture must be made
by an experienced orthopaedic surgeon. Lesions that do not represent a
risk for fracture may be treated with radiation or by appropriate chemotherapy
directed at the tumor. Lesions that are regarded as a risk for pathologic
fracture should be surgically stabilized on an elective basis before a
fracture occurs. The goals of surgery are to preserve stability and function
of the musculoskeletal system as well as alleviate pain. Emergency surgery
is done for spinal metastasis in the hope of preserving neurological function.
l Vinholes, J. et al., Effects of Bone Metastases on Bone Metabolism:
Implications for Diagnosis, Imaging and Assessment of Response to Cancer
Treatment, Cancer Treatment Reviews 22:289-331, 1996. 2 Stoll,
B. and Parbhoo, S., Bone Metastasis, Raven Press Books, Ltd.:New
York, NY, 1983, p. 14. 3 Vinholes, et al. 1/14/98 8:46 AM 1
New for physicians: A guide
to the assessment of pathological fracture risk.
Go to a specific
discussion of metastatic tumors arising from:
Kidney cancer (renal cell carcinoma)
Cancers of the GI tract (colon, stomach, etc.)
See a general discussion of skeletal metastases (spread of cancer to the
bones) of these cancers here.
See how to figure the risk of pathological fracture of a bone that has
been weakened by on of these metastatic lesions
Bisphosphonate medications: a powerful tool
that can prevent cancers from spreading to the bone, and slow the growth
cancers that have already spread to the bones.