The most common and debilitating feature of myeloma is the effect it has on bones throughout the body.
In fact, more than 70% of patients experience bone pain and have evidence of myeloma bone disease at the time of diagnosis – a condition shared by almost all patients at some point during the course of their myeloma.
But... isn't myeloma a blood cancer?
Yes. Even though it affects the bones, myeloma is considered a blood cancer because it develops in the blood's plasma cells, which are produced in the bone marrow.
How myeloma affects bones
The abnormal plasma cells (myeloma cells) in the bone marrow affect the surrounding bone, causing soft spots to develop where the bone structure has been damaged.
These soft spots, that can extend from the inner bone marrow to the outer surface of the bone, appear on standard bone x-rays as "holes" – referred to as osteolytic lesions. These lesions weaken the bone, causing pain and increasing the risk of fractures.
How bone destruction occurs in myeloma
Throughout our lives, our bones are constantly being remodeled by two types of complementary cells known as osteoblasts and osteoclasts.
Osteoclasts break down old bone, while osteoblasts form new bone to replace it.
Under normal conditions, both types of cells keep the rate of bone formation and bone breakdown equal, so that bone mass remains the same.
In myeloma, the rapid growth of abnormal plasma cells interferes with the production of osteoblasts (the bone-forming cells). At the same time, there is an increase in substances that activate the osteoclasts (the cells that break down bone).
In other words, bone loss is increased while bone repair and growth are decreased. The net result: bone is destroyed faster than it can be replaced.
As if that weren't enough, the osteoclasts (the cells that break down bone) produce their own signals that stimulate the growth of myeloma cells.
This vicious cycle of dependency between the myeloma cells and bone marrow cells (like the osteoclasts) results in a net loss of bone and the development of the osteolytic lesions found on myeloma patients' x-rays.
By better understanding these mechanisms, it may be possible some day to develop more effective treatments to interrupt, slow down, or stop the process that leads to bone disease and contributes to tumour cell growth and survival in myeloma.
For more information, download the Multiple Myeloma Patient Handbook
Designed to provide educational support to patients, caregivers, families, and friends, this handbook gives accurate, reliable, and clear information on myeloma. Topics cover its causes and effects, how it is diagnosed, and the treatment options available in Canada.
Download it now.