Multiple Myeloma
Weight Gain & Cancer Risk
Medical Author: Melissa Conrad Stöppler, MD
Medical Editor: William C. Shiel Jr., MD, FACP, FACR
Excess weight is a known risk factor for many chronic diseases, such as
diabetes and heart disease. Obesity has also been linked an increased risk for
developing some cancers. To clarify the effects of weight gain on cancer risk,
researchers in 2007 conducted an analysis of many studies reported in medical
journals that describe 282,137 cases of cancer. The researchers wanted to see if
weight gain had an effect on the risk for certain cancer types.
In particular, the researchers looked at the risk of cancer associated with a
weight gain corresponding to an increase of 5 kg/m2 in body mass index (BMI). In
terms of actual pounds gained, a man with a normal-range BMI of 23 would need to
gain 15 kg (33 lbs.) of weight, while a woman with a BMI of 23 would need to
gain 13 kg (28.6 lbs.) to correspond to an increase of 5 in the BMI.
The results, published in the Lancet in February 2008, revealed that weight
gain is positively associated with the risk of developing a variety of types of
cancer as described below.
For women, a weight gain corresponding to an increase of 5 in the BMI
resulted in a significant increase in risk for developing four cancer types:
In women, a weaker but still positive increase in cancer risk with weight
gain was demonstrated for the following cancer types:
What is multiple myeloma?
Multiple myeloma is
cancer that begins in plasma cells, a type of white blood cell. To
understand multiple myeloma, it is helpful to know about normal blood cells.
Normal blood cells
Most blood cells develop from cells in the
bone marrow called stem cells. Bone marrow is the soft material in the
center of most bones.
Stem cells mature into different types of blood cells. Each type has a
special function:
- White blood cells help fight infection. There are several types of white
blood cells.
- Red blood cells carry
oxygen to tissues throughout the body.
- Platelets help form blood clots that control bleeding.
Plasma cells are white blood cells that make antibodies. Antibodies are part
of the immune system. They
work with other parts of the immune system to help protect the body from germs
and other harmful substances. Each type of
plasma cell makes a different
antibody.
Myeloma cells
Myeloma, like other cancers, begins in cells. Normally, cells grow and
divide to form new cells as the body needs them. When cells grow old, they
die, and new cells take their place. In cancer, this orderly process goes
wrong. New cells form when the body does not need them, and old cells do not
die when they should. These extra cells can form a mass of tissue called a
growth or tumor.
Myeloma begins when a plasma cell becomes abnormal. The abnormal cell divides
to make copies of itself. The new cells divide again and again, making more and
more abnormal cells. The abnormal plasma cells are myeloma cells. Myeloma cells
make antibodies called M proteins.
In time, myeloma cells collect in the bone marrow. They may crowd out normal
blood cells. Myeloma cells also collect in the solid part of the bone. The
disease is called "multiple myeloma" because it affects many bones. (If myeloma
cells collect in only one bone, the single mass is called a
plasmacytoma.)
Multiple myeloma is the most common type of plasma cell tumor. This booklet
does not deal with other kinds of plasma cell tumors. The Cancer Information
Service (1-800-4-CANCER) can send information about those diseases.
Multiple myeloma is not
bone cancer. Although multiple myeloma affects the bones, it begins in
blood cells, not bone cells.
Bone cancer is a different disease. It begins in bone cells, not blood cells.
Bone cancer is diagnosed and treated differently from multiple myeloma.
The NCI's fact sheet "Bone Cancer: Questions and Answers" provides
information about bone cancer. This fact sheet and other materials are available
from the Cancer Information Service (1-800-4-CANCER) and on NCI's Web site (http://www.cancer.gov).
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