Absolute Neutrophil Count (ANC) for Cancer Treatment

The absolute neutrophil count (ANC) assesses the number of neutrophils (white blood cells that are important in fighting infection) in your bloodstream. Neutrophil counts may be lower than normal for any number of reasons, including both diseases and treatments. A drop in the ANC may occur as a result of cancer chemotherapy, for instance.

A healthy person has an ANC between 1,500 and 6,000. Your absolute neutrophil count can be calculated using a common blood test called the complete blood count (CBC). The CBC gives your doctor all of your numbers for red blood cells, white blood cells (WBCs), and platelets—the small bits of cellular material that help to control bleeding.

The ANC is found by multiplying the total white blood cell count by the percent that are neutrophils.

In the lab, modern blood counting instruments are sophisticated enough to produce an automated WBC differential and report the ANC. A microscopic WBC differential may also be performed by lab professionals to confirm findings or give more details.

They may further report "bands" and "segs," which are immature and mature neutrophils. These would be added together. It is like adding together the number of calves and adults to get a headcount for cattle—bands are the more immature form of segmented neutrophils (segs).

Interpreting ANC Results

It’s possible that your total WBC count is normal but your neutrophil count is low. However, since neutrophils normally have the largest piece of the pie in terms of total white blood cells, the WBC count is usually also low when the neutrophil count is low.

Neutrophils are the most numerous WBCs in the bloodstream of healthy individuals, usually constituting more than 50% of the white blood cell count. They are the most important WBC in fighting infection.

The presence of abnormally small numbers of neutrophils in the circulating blood is called neutropenia. There are differing degrees of neutropenia, depending on how low your ANC goes.

According to the American Cancer Society, a healthy person has an ANC between 2,500 and 6,000. When the ANC drops below 1,000, there may be some increased risk of infection, so your doctor will keep an eye on your counts very closely. You are at a much greater risk of infection when the ANC is below 500.

Bone marrow normally makes your blood cells, including neutrophils. Life-saving cancer therapies including chemotherapy and radiation may target rapidly growing cells and adversely impact the production of neutrophils—and so a drop in ANC is sometimes an expected side effect.

In some cases, when ANC is expected to become low, or when it is already low, antibiotics may be given to prevent infection. Another drug that may be given is a growth factor—medicine that helps boost your neutrophil production.

Low ANC Symptoms

Simply having a low WBC count or even a low absolute neutrophil count does not necessarily produce noticeable symptoms. That is why it is so important to be alert to the possibility of symptoms of infection when your neutrophils are depleted. Unfortunately, as the ANC gets lower, many of these signs may not be prominent when an infection starts.

Here are some of the signs and symptoms of infection that you can be vigilant about:

• Fever
• Chills
• Cough
• Trouble breathing
• Diarrhea
• Pain

If there is a central venous access device (central line or port), check for redness, swelling, pain, or pus at the site, where the tube enters the body. A person with a low ANC might not have redness or pus, but could still have an infection.

If your ANC goes down to 1,000 or lower and you have a fever, many clinicians take the leap of faith that there is an infection. Antibiotic treatment is usually started immediately, often before the infection's source has been identified.

Then it becomes a process of narrowing down the likely suspects from among the possible infectious pathogens while continuing to treat with the most inclusive therapies.

As certain clues emerge, doctors may be able to determine the exact site and cause of the infection and which pathogens may be involved. In this way, they can select the treatment that’s most likely to work. This may mean that the antibiotic that was given at first will be switched to one that is more tailor-made for the offending germ.

Causes of Low ANC

Depression of WBCs, including specifically the neutrophils, is the toxicity of many different anti-cancer therapies. A low ANC can also be a manifestation or sign of the underlying disease, as is the case in some types of blood cancer.

Additionally, a low ANC may occur in the treatment of various other chronic illnesses, such as autoimmune disorders like rheumatoid arthritis.

For instance, one of the treatments for rheumatoid arthritis, tocilizumab, blocks a cell signal known as IL-6. It has been linked to lower ANCs, though decreases in neutrophil counts in patients taking tocilizumab do not appear to be associated with serious infections. Steps are taken to lower the risk of infection.

Finally, very rarely, it is possible for people can have severe chronic primary neutropenia. This disorder is not well understood. It has a female predominance, and it appears that despite low ANC, severe infections are rare, and patients have an overall favorable outcome.