Multiple myeloma (MM) is a type of blood cancer that affects plasma cells in the bone marrow. It damages the bones and affects the production of healthy blood cells. Those with MM can develop lesions in their bones.
In MM, the cancerous plasma cells overproduce certain proteins that encourage the breakdown of bone tissue. This can cause the bones to weaken and develop holes known as “lytic lesions.” Bones with lytic lesions are more susceptible to fractures.
Lytic lesions are treatable, though they may never fully heal. However, treatments can help stabilize existing fractures, slow the progression of MM bone disease, and reduce the risk of severe bone complications.
This article describes the types of bone lesions that MM can cause, including what these lesions look like and how they develop.
It also outlines the symptoms of MM bone lesions and provides information on diagnosis, treatment, and outlook.
MM can weaken bones, causing them to develop holes. Doctors refer to these holes as lytic lesions.
According to the International Myeloma Foundation (IMF), more than 8 in 10 people with MM develop bone problems during the course of the disease, and around 7 in 10 of these people experience lytic lesions in the spine.
Other common areas for lytic lesions to develop include:
- the pelvis
- the ribs
- the skull
- the long bones of the arms and legs
Bones with lytic lesions are more susceptible to breakage from minor pressure or injury.
What are focal lesions?
Lytic lesions begin as focal lesions.
Doctors use the term “focal lesions” to refer to an abnormal area of bone marrow that will develop into a lytic lesion within 18–24 months.
In a healthy skeleton, there is a balance between the breakdown of old bone tissue and the generation of new bone tissue.
The cells that help to break down bone tissue are known as osteoclasts, and the cells that help to generate new bone tissue are known as osteoblasts.
A protein — RANK ligand, or RANK-L — stimulates osteoclasts to break down bone tissue. Osteoblasts produce the protein osteoprotegerin (OPG), which inactivates RANK-L. In this way, osteoblasts help to prevent excess breakdown of bone tissue.
A 2020 review explains that in MM, the cancerous cells interact with the bone marrow microenvironment in a way that leads to increased expression of RANK-L and decreased expression of OPG. This, in turn, leads to too much bone breakdown and too little bone regeneration.
In MM bone disease, the bone tissue breaks down at a rapid rate, leaking calcium into the bloodstream. This can lead to hypercalcemia, which is the medical term for high levels of calcium in the blood.
Symptoms of hypercalcemia
- dehydration
- extreme thirst
- excessive urination
- kidney problems
- abdominal pain
- severe constipation
- loss of appetite
- weakness
- drowsiness
- confusion
A person with MM bone disease may also experience the following skeletal symptoms: Bone pain, which can occur in any bone, but
Doctors may use the following imaging tests to diagnose and monitor MM-related bone disease:
- X-ray: This type of imaging is the standard of care for diagnosing bone disease in suspected MM.
- Computerized tomography (CT) scan: The IMF notes that the National Comprehensive Cancer Network lists CT scans as one of two preferred imaging tests for diagnosing MM bone disease.
- Magnetic resonance imaging (MRI) scan: This imaging test is sensitive to detecting early focal lesions in the bone marrow.
- Positron emission tomography (PET) scan: This type of scan can detect changes to bones and soft tissues. Doctors may use PET scans to diagnose MM bone lesions and assess treatment responses.
According to the IMF, a person who has the following should receive treatment for MM bone disease: More than one focal lesion measuring at least 5 millimeters showing on an MRI scan and one or more lytic bone lesions showing on a CT scan.
The treatment for MM bone disease consists of two steps: Treating the myeloma and using medications — bone-modifying agents (BMAs) — to prevent further bone loss.
Medications
Two types of BMAs that doctors use to treat MM bone disease are bisphosphonates and monoclonal antibodies (MAs).
Bisphosphonates are small molecules that bind to the surface of damaged bones, where they inhibit and destroy osteoclasts. Examples include Aredia (pamidronate) and Zometa (zoledronic acid or zoledronate). Doctors administer these medications intravenously — directly into the vein.
MAs target certain proteins in the body. The MA known as Geva (denosumab) targets the RANK-L protein. It is a subcutaneous injection that doctors administer monthly into the fatty tissue under the skin.
Surgery
Lytic lesions in the spine can cause vertebral compression fractures (VCFs), which can result in pain and disability.
Moreover, VCFs may cause the vertebral bones to collapse and press on the spinal cord. Spinal cord compression is a medical emergency that requires immediate treatment.
There are two types of minimally invasive surgery that may help to treat VCFs — vertebroplasty and balloon kyphoplasty.
Both procedures involve injecting a special cement into the weakened part of the vertebra to help strengthen and stabilize the area and reduce pain.
Lytic lesions in the long bones of the arms or legs may also require surgery to help reinforce and stabilize the bone.
Lytic lesions in the spine persist despite successful treatment for MM.
Although the hole fills in to some degree with scar tissue and calcium, it does not rebuild normal bone tissue. As a result, the area of the lytic lesion remains weak.
Bisphosphonates can strengthen the bones, though they do not completely heal lytic lesions. However, kyphoplasty can help to fill the hole, adding extra strength and stability.
According to a
However, the authors note that bisphosphonates can reduce the risk of SREs and severe bone complications.
A person can speak with a doctor or treatment team for more information regarding their individual treatment options and outlook.
Multiple myeloma (MM) is a type of cancer that affects the blood and bone marrow. Blood disorders and bone disease are common complications of MM.
In MM, cancerous plasma cells overproduce proteins that encourage the breakdown of bone tissue. As the bone degrades, it can form a hole or “lytic lesion.”
These lesions weaken the bones, making them more susceptible to fractures and associated complications.
Treatments can help to slow the progression of bone disease in MM and reduce the risk of severe bone complications, though they cannot completely heal lytic lesions.
However, minimally invasive procedures, such as vertebroplasty and kyphoplasty, can help strengthen and stabilize lytic lesions in the spine. This may help to alleviate pain and disability.