How does bone cancer start?
We have different types of cells that make up our bones. Bone cancer is a type of cancer that starts when these cells begin to grow out of control.
Bone cancer can begin in one of two ways. The more common kind of bone cancer is one that begins somewhere else in the body and goes to the bone. In those cases, the cancer cells will look like the ones from the organ the cancer spread from. This tends to occur with advanced-stage breast, prostate, and lung cancer.
The less common bone cancer is primary bone cancer, which originates in the bone. Types of primary bone cancer include osteosarcoma, chondrosarcoma, and Ewing sarcoma.
What cells do we have in our bones and how do they become cancerous?
We have osteoblast and osteoclast cells. Osteoblast cells form bone, and osteoclasts eat old bone to essentially remodel the bone. We also have other cells, such as lipoblasts that come from fat, and cartilage cells that act like shock absorbers to protect our joints and bones.
All these cells come from mesenchymal stem cells, which are cells that help make and repair skeletal tissues, like cartilage, bone, and fat, in the bone marrow. Bone marrow, at the center of our bones, contains blood vessels.
When someone develops cancer in the bone, one of these cells, and oftentimes we think it is the mesenchymal stem cells, suddenly grows out of control, causing chaos. This chaos eventually becomes cancer, and that cancer is capable of invading and leaving the bone, entering other parts of the body nearby.
What are the symptoms?
The major symptom to look out for is bone pain, which is not like other types of functional pain, such as when you lift something and feel like your muscles ache. Bone pain is a little more insidious, meaning that it can be subtle in nature and feels like the pain is there even when you are not doing activities. Often people will express having this kind of bone pain while they are resting. At night, the pain will wake them from sleeping because it hurts. It is a dull, aching, even throbbing-like pain in the bone, like a toothache.
A symptom of a late finding of cancer in the bone is swelling, more stiffness, and loss of motion. This could be when the tumor starts to grow outside the bone.
Unfortunately, in certain areas of the body, you will not notice cancer growing because it is deep at first. You will not be able to physically see a swollen area.
What are the differences between the types of primary bone cancers?
Osteosarcoma, the most common kind in people between the ages of 10 and 30, arises from the osteo cells, the cells that produce osteoblast, with tumors developing often in the arms, legs, or pelvis.
The second most common is chondrosarcoma, which begins in the cells that produce cartilage. It can develop most commonly as people get older and in the pelvic bones, legs, or arms, as well as other parts of the body, such as shoulder blades or ribs.
With Ewing sarcoma, we do not fully understand what the originating cells are, but they form this small, round blue cell cancer in the bone. The cancer can also develop in tissues and organs in the body. Ewing sarcoma is common in children, adolescents, and young adults.
Who is at risk for bone cancer?
There are rare genetic abnormalities, but I would say that 99% of patients that present with primary bone cancer have no genetic predisposition.
The genetic risk that we know about is a condition called Li-Fraumeni Syndrome, which people are born with. It is a mutation in the gene that puts you at risk for different kinds of cancer, including bone cancer, like osteosarcoma. Another is the retinoblastoma gene. Patients born with this gene usually know because they get retinoblastoma, which is a cancer of the eye, at an early age. And then they are at risk for developing osteosarcoma later in life.
How is bone cancer detected, and what does treatment look like?
When someone presents to their physician with bone pain, the first step is to get an X-ray. The X-ray would then show us that something is probably going on in the bone. Then we schedule an MRI to get more detailed imaging, where we can look at the bone and assess the area, too. To confirm the diagnosis, we would do a biopsy — when tissue from the bone is removed and examined.
Treatment is variable. Almost always there is surgery for primary bone cancer and depending on the type of cancer, there could be a need for chemotherapy, which works to remove cancer cells, and occasionally radiation therapy, a treatment to shrink tumors.
What should people keep in mind?
What is helpful in terms of detection is that bone cancer is almost always associated with bone pain. Bones have a lot of nerve endings in them, so they are sensitive to the changes going on within them. If people are having that persistent, aching pain that is not resolving, they should visit their doctor and ask for an X-ray. Doing this can help with early detection.