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BONE CANCER
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BONE CANCER
While most cancer in bone is from spread of other cancers there (such as lung or breast cancer) certain patients get "primary bone cancer". This means the cancer actually originates in the bone. Historically the treatment of these cancers was drastic amputation of a limb or other major operation to remove the bone. Unfortunately, patients often died anyway. However, newer research has shown more effective treatment for bone cancers; patients today are often cured while keeping their limb.
There are two basic types of bone in the body: flat bone and long long. Flat bones include those in
the skull, vertebrae and ribs, while long bones are found in the extremities. The central skeleton
contains the flat bones, and is called the 'axial" skeleton; the limbs contain the long bones
which are called the "appendicular" skeleton.
While the outer shell, or "Otable" of each bone is the hard cortex, the inside of both
flat and long bones is made of up the soft "marrow." The marrow is basically little
spicules of bone with blood forming cells clinging to them, so it is very rich in blood. The marrow
contains "stem cells," which are the 'precursor (first) blood cells from which all others
arise. The cortex of the bone has nerves traveling through it, accounting for bone pain when the
bone is injured. When a bone fractures, it forms a hard "callous" around the break, and
amazingly this is even stroqger than the bone before breakage!
A balance is kept between the free calcium in the blood and the calcium in bone by hormones. If the
blood calcium is too low, then some is reabsorbed from bone through the action of "parathyroid
hormone" (PTH), produced by small glands in the thyroid. If the blood calcium is too high, it
is deposited into bone by the hormone "Ocalcitonin," also from the thyroid. The laying
down of calcium in bone also requires active vitamin D, and a shortage of this during childhood
results in "rickets." Vitamin D is converted from its dietary to active form by sunlight,
but only requires a very brief exposure. There is a balance between phosphorus and calcium in the
blood: when one goes up the other goes down. People with kidney failure, on dialysis, have a
difficult time clearing their blood of phosphorus, and this results in calcium being leached out of
bone. Too much phosphoric acid in the diet, from soda-pop, can also weaken bone. In women, the
deposition of calcium into bone requires estrogen. calcium and exercise. and if lacking these women
tend to get "osteoporesis" (brittle bones) after menopause.
What is Bone Cancer?
Normally, the cells informing the bone cortex divide very rapidly from womb life through puberty,
and then slow down dramatically during adult life. The major growth occurs at the ends of the long
bones, called the "epiphysis": where initially new cartilage grows: this is gradually
calcified by osteoblasts into hard bone. If the "epiphyseal plate" is damaged in
childhood, by injury or medication, this will stunt that bone's growth. The long shaft of a bone is
called the "diaphysis', and the area between the epiphysis and diaphysis is called the
"metaphysis." These areas are important to know since particular bone tumors have a
predilection to arise in particular areas of the bone, as will be seen. The cells inside the bone
marrow, which form the blood cells, must continue to divide very rapidly throughout life, since
white blood cells may normally live as little as 10 hours. The types of cancer that arise from these
are lymphomas, leukemias, and myelomas, are are NOT considered primary bone cancer; they are
different topics.
The control of new bone formation is by the "genes," sequences of DNA which are
themselves packed into larger chromosomes in each cell. If there is damage to the genes. a given
cell may start dividing out of control. Bone cancer starts in just one cell. This cell starts
dividing in a haphazard manner, eventually forming a clump called a "tumor." A tumor
simply means a swelling; it can be caused by infection or cancer or injury. If a tumor only grows in
it's local area, and does not have the capacity to spread distantly, it is called "benign"
and is not cancer. If, however, a tumor has the capability to spread distantly to other organs, it
is called "malignant" and this is cancer. The actual process of cancer spread is called
"metastasis," and may occur to any place in the body. Sometimes, a tumor in bone may start
as benign, but further DNA damage can cause it to become malignant; this process is called
"malignant degeneration." Cancer kills by anemia. infection and debility, and by spreading
to and interfering with the function of critical body areas, such as the lung and brain. Any cancer
that is not successfully treated will eventually lead to the patient's demise, but this may be a
very rapid (weeks) or very slow (many years) process. Also, for bone some tumors have a varying
degree of aggressiveness, and the same type of tumor (i.e. Giant Cell Tumor) may range from indolent
to aggressive in different patients. Thus, even true bone cancers may be classed as merely
"bone tumors," which doesn't say if it is a true cancer or not. Ar, essential of the
evaluation is to try to detemine how aggressive. or "malignant," the tumor is.
It is important to note that this transcript discusses PRIMARY bone cancers, which means those that
arise in the cortex of the bone. Cancers originating in other areas may have a strong predilection
to spread to bone. such as prostate, lung and breast cancer. The treatment for these when they have
metastasized to bone is discussed under the transcripts dealing with those particular cancers. Also,
some cancers arise from cells which normally live in bone, such as lymphomas, myelomas,
plasmacytomas. and leukemias from the blood cells within the bone marrow. These are also discussed
in their own transcripts, as they are not primary bone cancers.
How Common Is Bone Cancer?
There are about 500 new cases of primary bone cancer each year in the U.S.A, making this a rare
cancer. Bone cancers represent 3% of childhood cancers with about 200 new cases per year. The
majority of cases are in the second decade (during adolescence), but there is a second peak in the
6th decade. About 3 per 100.000 people will ever develop a primary bone cancer. In children under 10
years old, only 20% of bone tumors are malignant. However, in adults malignant bone tumors are twice
as common as benign bone tumors. Recall that most malignant tumors found in bone have spread there
from another organ, and so are not primary bone cancer.
What are the Common Types of Bone Cancer?
If multiple myetoma is considered a primary bone tumor (even though it arises in the marrow and not
the cortex) then it represents 40% of bone tumors. Classically, the major common types of bone
cancer are "Chondrosarcoma" (arising from cartilage), "Osteosarcoma" (arising
from bone), "Fibrosarcoma" (arising from scar tissue), "Liposarcoma" (arising
from fat), "Ewing's Sarcoma" (from primitive cells) and the increasingly popular
"Malignant Fibrous Histiocytoma" (MFH) of disputed origin. Rare types exist, like
"Hemangiopericytoma" from blood vessels within the bone, "Malignant Giant Cell
Tumor," and "Adamantinoma" (from enamel in teeth). It is important to note that
sub-varieties of the above types exist, and there may be a mixture of elements in a given tumor.
Primary examples of this are "osteochandrosarcoma" which is made of up both bone and
cartilage, and 'fibrochondrosarcoma" made up of both fibrous tissue and cartilage. Another
crucial thing to know is that there has been a gradual "reclassification" of bone cancers,
so that MFH, which was once a rare diagnosis, is now the most common in many series! Also. various
pathologists (doctors who make diagnosis from tissue samples) may give different diagnosis from
examining the same bone tumor under the microscope! In fact. there is as much as a 20% disagreement
by even expert pathologists when classifying biopsies (samples) of bone tumors from the same
patient.
It is crucial to be educated and make the proper treatment choices for bone cancer. This can make the difference between keeping or loosing the limb, or life and death. It is important to have the peace-of-mind of knowing you have done everything possible to fight this cancer successfully.
The Cancer Group Institute's materials explain, in plain English, the definition, types, frequency, symptoms, evaluation, historical treatment and results, and latest effective treatments and results for bone cancer. We describe surgery, radiation and chemotherapy and tell you their results. We tell you everything you need to know to help you make the right decisions today for a bone cancer problem.
