What is the Relationship Between Anemia and Cancer?

Anemia is a fatigue-inducing condition that can be caused by many things, including low levels of iron or the vitamin B12, malaria, or even lead poisoning. But in the context of a diagnosis of cancer, anemia can be caused by the cancer itself, chemotherapy treatments, or both.

The bone marrow is the factory responsible for producing all blood cells, says Allison F. O’Neill, MD, Director of the Pediatric Liver Tumor Program at Dana-Farber/Boston Children’s Cancer and Blood Disorders Center. Red blood cells carry oxygen to and from the organs in the body; in the case of anemia, there are too few of these red blood cells. Anemia can be caused by loss of red blood cells (i.e. bleeding), destruction of red blood cells, or the inability to produce red blood cells.  Symptoms associated with anemia include dizziness, fatigue, chest pain, shortness of breath or a racing heart.

Red blood cells.
Red blood cells.

Here, O’Neill and David P. Steensma, MD, a hematologic oncologist at Dana-Farber, explain the connection between anemia and cancer.

What Cancers are Associated with Anemia?

Cancers that involve the marrow space, such as leukemia or lymphoma, compete with the marrow’s function and interfere with normal red blood cell production. This, then, causes anemia, O’Neill says.

Allison F. O’Neill, MD.
Allison F. O’Neill, MD.

That’s also why cancers, like breast and prostate cancer, can metastasize to the bone marrow, which may also cause anemia, according to Steensma.

But bone marrow doesn’t necessarily need to be involved for anemia to be present in patients. Cancers of the gastrointestinal (GI) system, like colon and stomach cancers, can lead to anemia because of frequent bleeding often associated with those types of cancer.

If you detect anemia in a person over age 50 and there’s no other easy way to explain it, that could be a sign of cancer in the gastrointestinal system.

Occasionally, rapidly growing cancers can also bleed into the center of a tumor. “This might be the cause of an acute drop in blood levels, and an acute cause of anemia,” O’Neill says.

Do Cancer Treatments Lead to Anemia?

Often, yes. Chemotherapy agents “target rapidly dividing cells, which by definition are cancer cells. However, they are non-specific in that they also attack other rapidly dividing cells in the body: hair follicles, the lining of the GI tract, and blood cells,” says O’Neill.

David P. Steensma, MD.
David P. Steensma, MD.

If red blood cell counts get too low, patients can receive blood transfusions, or red blood cell growth factors like Epoetin or Darbepoetin alfa, which are administrated weekly or once every three weeks.

Steensma warns that for cancer-caused anemia, just taking iron pills or eating more red meat usually won’t help. Except in the case of bleeding, anemia associated with cancer is usually not due to iron deficiency, so trying to increase your iron levels won’t have much effect. 

Not Everyone With Anemia Has Cancer

Both physicians stress that being anemic does not mean that you have cancer, or that you will develop cancer. “Cancer is way down on the list in terms of anemia’s most common causes,” says Steensma.

It can often show up in menstruating women, particularly athletes. Globally, the most common causes of anemia are malaria, inherited conditions like sickle cell disease or thalassemia, and parasites like hookworm.

“Cancer is commonly associated with anemia, but anemia has many other causes that are not cancer,” says Steensma.