Metastatic multiple myeloma is a form of cancer of the bone marrow that has spread to other parts of the body. Common sites of metastasis include the skin, muscles, and lymph nodes.

Multiple myeloma is a type of cancer that originates in the bone marrow. Metastasis is when cancer cells from the original site spread to other parts of the body.

This article discusses metastatic multiple myeloma in more detail. It also looks at the most common sites the cancer may spread to, symptoms, treatment, and potential outlook.

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Plasma cells are types of white blood cells that originate in bone marrow and produce antibodies to help the body fight off infection. Multiple myeloma occurs when the plasma cells become too large, start to grow irregularly, and become cancerous.

Multiple myeloma is the most common type of cancer of the plasma cells and can affect any bone in the body.

According to the Canadian Cancer Society, the most common bones that this cancer affects include the:

  • spine
  • skull
  • scapula (shoulder blade)
  • ribs
  • hips
  • humerus (upper arm bone)
  • sternum (breastbone)
  • femur (upper leg bone)

Metastatic multiple myeloma is when multiple myeloma has spread from the original site in the bone marrow to other parts of the body.

Research from 2021 suggests multiple myeloma is the 14th most common type of cancer in the United States.

The American Cancer Society estimates that approximately 35,780 people in the United States will receive a multiple myeloma diagnosis in 2024.

Research from 2022 suggests that the most common places that multiple myeloma can spread to outside of the bones may include:

The cancerous plasma cells of multiple myeloma typically grow irregularly, leaving insufficient space in the bone marrow for other red and white blood cells that the body needs. This can lead to a person having a low blood count.

Healthy plasma cells produce antibodies to help the body fight off infections. Cancerous multiple myeloma cells produce a different type of antibody that is not effective at protecting the body from infection. These ineffective antibodies can also cause damage to the kidneys, which can lead to kidney failure.

The multiple myeloma cells can also interfere with the bone renewal process. This can result in the body breaking down old bone too quickly, before the body has had time to produce new bone to replace it.

Therefore, a person with metastatic multiple myeloma may experience bone weakness and be more vulnerable to fractures. It can also lead to high levels of calcium in the blood.

A person with metastatic multiple myeloma may not experience any symptoms.

However, the features of metastatic multiple myeloma — such as low blood count, weakened immune system, and high levels of calcium — can lead to several symptoms, including:

The type of treatment for metastatic multiple myeloma may depend on where in the body the cancer has spread.

A person without any symptoms may not require treatment straight away. When a person does require treatment, typical options can include:

  • chemotherapy, which can stop cancer cells from growing
  • stem cell transplant, in which a person receives new, healthy blood cells to replace any that chemotherapy treatment may have destroyed
  • targeted therapy, which can target and kill specific cancer cells
  • immunotherapy, which activates the immune system so that the body can fight off cancer cells
  • corticosteroid therapy, which can slow the growth of multiple myeloma cancer cells
  • radiation therapy, which uses high energy X-rays to kill cancer cells

The 5-year relative survival rate for myeloma that has spread to distant body parts is 60.4% at diagnosis, as per data from 2014 to 2020. This figure is from the National Cancer Institute’s Surveillance, Epidemiology, and End Results (SEER) program database.

However, each person’s outlook will vary depending on where the multiple myeloma has metastasized to and other individual health factors.

A person may wish to speak with their doctor to find out more about their individual outlook.

Metastatic multiple myeloma is a form of cancer. It typically begins in a type of white blood cell in the bone marrow that has spread to other parts of the body.

Metastatic multiple myeloma commonly occurs in the skin, muscles, central nervous system, lymph nodes, and liver.

Symptoms of metastatic multiple myeloma can include shortness of breath, fatigue, frequent infections, bone pain, bone weakness, excessive bleeding, and weight loss.

Treatments for metastatic multiple myeloma can include chemotherapy, radiation therapy, stem cell transplant, and immunotherapy.

Each person’s outlook varies depending on a range of factors, so it is best to contact a doctor for further information.