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Low White Blood Cell Counts and Infection Risk
Brian Wojciechowski, M.D.
March 14, 2019

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Brian Wojciechowski, M.D., practices medical oncology in Delaware County, Pennsylvania at Riddle, Taylor, and Crozer hospitals and also serves as's medical adviser. A native of South Philadelphia, he trained at Temple University School of Medicine and Lankenau Medical Center. Dr. Wojciechowski is a sought-after speaker on the topics of medical ethics and the biology of cancer.

Listen to the podcast to hear Dr. Wojciechowski explain:

  • the different types of white blood cells and what they do in the body
  • how chemotherapy and targeted therapy medicines lower white blood cell counts
  • why low white blood cell counts raise the risk of infection
  • how doctors monitor white blood cell counts
  • symptoms of infection to watch out for
  • steps you can take during chemotherapy to keep your risk of infection as low as it can be

Running time: 12:19

Show Full Transcript

Jamie DePolo: Hello, everyone, I’m Jamie DePolo, senior editor at Our guest for today’s podcast is Brian Wojciechowski, M.D. He practices medical oncology in Delaware County, Pennsylvania at Riddle, Taylor, and Crozer Hospitals and also serves as’s medical adviser. A native of south Philadelphia, he trained at Temple University School of Medicine and Lankenau Medical Center. Dr. Wojciechowski is a sought after speaker on the topics of medical ethics and the biology of cancer. 

Today, he joins us to talk about white blood cells, how certain treatments lower white blood cell counts, and why low white blood cell counts can raise the risk of infection.

Dr. Brian, welcome to the podcast!

Dr. Wojciechowski: Thanks, it’s great to be back, Jamie.

Jamie DePolo: Let’s start with some basics. Can you tell us first, what are white blood cells, how many types of white blood cells do we have in our bodies, and exactly what do these white blood cells do?

Dr. Wojciechowski: Well, white blood cells are tiny little cells that are made in the bone marrow, and their main function is to prevent infection, to fight off bacteria and viruses and other invaders. They basically constitute the front line of our immune system. There are several different types of white blood cells that normally circulate in your blood, including neutrophils, lymphocytes, eosinophils, monocytes, and a few others. There’s a number of other different white blood cells that only, in a normal instance, hang out in the bone marrow or the lymph nodes. They don’t usually circulate in the blood stream in normal states.

We are most concerned with two types of white blood cells. One is called neutrophils, and the other is called lymphocytes. Like I said, the function of white blood cells is to fight off infections, viruses, bacteria, fungus, that sort of thing. They also play a role in wound healing, but the main thing is fighting infection and being the body’s first line of defense.

Jamie DePolo: I know that many chemotherapy medicines and, I think, almost all of the targeted therapy medicines that are used to treat breast cancer can lower white blood cell counts. Can you talk a little bit about how that happens, and do the medicines lower all the types of white blood cells that you talked about, or is it just the couple that we’re concerned about?

Dr. Wojciechowski: So the reason these drugs lower white blood cell counts is that these drugs affect something called the cell cycle. The cell cycle is the normal healthy process by which cells grow and divide. So chemotherapy and targeted therapy drugs, many of them interfere with that normal cell process of growth and division. And this is a good thing because the goal is to kill cancer cells, which are growing rapidly. But because some of them are kind of nonspecific, they don’t always just target cancer cells, and they can hit the cell cycle in the normal healthy cells of the body, such as hair follicles, cells in the colon, which can cause diarrhea, and of course, white blood cells and other blood cells. So chemotherapy tends to lower just the neutrophils, and some of the targeted therapy drugs can lower neutrophils but they can also lower lymphocytes.

Jamie DePolo: If you could tell us a bit about… I’m assuming those two white blood cells do sort of different things, or do they do basically the same thing?

Dr. Wojciechowski: They both basically fight certain types of infections. Some are more specific than others. There is a lot of overlap, but they’re basically very similar in function.

Jamie DePolo: I want to ask, too, because I believe I’ve read that a lot of the chemotherapy medicines as well as the targeted therapies, they’re targeting cells that are growing and dividing rapidly. In your previous answer you said that some of these medicines aren’t that specific. So is that indeed correct? Then that tells me why, in the mouth, because the cells in the mouth are turning over quickly, hair cells turn over quickly, colon cells, stomach cells. Is that part of the answer to that?

Dr. Wojciechowski: Yes, so any cell that has a rapid turnover, that is turning over, that is growing quickly is going to be vulnerable to damage by chemotherapy. For example, skin cells don’t grow that quickly, bone cells don’t grow quickly, nerve cells don’t grow quickly. So they tend to be less susceptible to at least the immediate effects of chemotherapy.

Jamie DePolo: If somebody has low white blood cell counts because they’re being treated with one of these medicines, does the person automatically have a higher risk of infection? Is that something that you, as an oncologist, just assume and then act accordingly with the people that you’re treating?

Dr. Wojciechowski: Well, I get particularly worried when the neutrophil count goes below 500. We call that severe neutropenia. That’s where there is a high risk of infection, and we start to take certain steps to mitigate that. If someone has severe neutropenia plus a fever, that’s a medical emergency because there will be a very high chance of an infection — a serious infection, particularly a bloodstream infection or a severe lung infection — and I usually send those patients right to the emergency room.

Now, if the neutrophils are low but not quite below 500, I really don’t worry quite as much.

Jamie DePolo: So that’s the cutoff?

Dr. Wojciechowski: Yes, it’s really a matter of degree. How low are the white cells?

Jamie DePolo: I know when people are in treatment, your doctor monitors your white blood cells and usually, I think, your complete blood cell counts. So how often is that done? Is it every day, is it once a month, is it once a week, to see where that lymphocyte level is?

Dr. Wojciechowski: Yeah, it depends on what medicine they’re getting. So for example, if one of my breast cancer patients is getting chemotherapy every 2 weeks, I’m checking their complete blood count every 2 weeks. If they’re on a 3-week regimen, it’s every 3 weeks with a quick visit in between, maybe at day 10, so 2 days out of 3 weeks in that case. If they’re on an oral targeted medicine, like a pill, it might be as frequently as once a month.

Jamie DePolo: Is that just a simple blood draw? Is that something that somebody could have done at an infusion center? Do they have to make a special trip? How does that usually work?

Dr. Wojciechowski: Typically, at the office of an oncologist, or the chemo doctor, the patient will come in and get their blood drawn. And we run it right there, because we want to know what that count is before they get their chemotherapy.

Jamie DePolo: Oh, I see. Would chemotherapy ever be, say, delayed, halted, or dose lowered because of low white blood cell counts?

Dr. Wojciechowski: Yeah, that does happen fairly often. When we’re treating women in the early stages of breast cancer, we typically give them white blood cell growth factors to try and prevent getting to that place in the first place. But sometimes we do have to delay treatment.

Jamie DePolo: Those medicines, would that be something like Neupogen?

Dr. Wojciechowski: Yes, Neupogen; Neulasta; Neulasta OBI, which is the on-body injector; Fulfilla; Zarzio — those are biosimilars. So there’s a number of different drugs we can use.

Jamie DePolo: So remind me again, do you usually wait until the white blood cell counts start dropping before you would start somebody on those medicines, or is it almost given as a preventive?

Dr. Wojciechowski: If we’re doing an aggressive chemotherapy regimen where, say, a woman is getting two or three drugs at once, we will generally do it pre-emptively. So she’ll get the booster shot the next day or a few days later depending on which drug we use, which is often dictated by insurance.

Jamie DePolo: If somebody is in treatment with particular medicines that are known to really reduce white blood cell counts, what are the symptoms that the person should look out for? I know you mentioned a low white blood cell count with a fever earlier, but say somebody is not really aware of their white blood cell count but is in treatment. If they have a fever should they contact their doctor immediately? Are there other things they should be looking out for?

Dr. Wojciechowski: Fever is the biggest thing, Jamie. That’s always an emergency with a cancer patient on chemo. Anytime there’s a fever — I usually tell my patients over 100.5, but over 100 is probably a decent cutoff for most people — that person should call their doctor right away, even if it’s in the middle of the night. So fever is the biggest thing. But also any other sign of infection, whether it’s something vague like sweats or chills, shakes, or just not feeling well, to something very specific like burning when you urinate, cough, chest pain, that sort of thing.

Jamie DePolo: Are there any things that a person who’s in chemo can do to lower their risk of infection aside from taking a medicine? Are there things they can do in their daily life, or things they should avoid, or anything like that?

Dr. Wojciechowski: Yeah, precaution-wise, I tell my patients to avoid someone who is obviously sick. And if they have to go out in large crowds, it’s not a bad idea to put on a mask. You can get masks pretty cheaply at the drug store. I don’t think people need to completely avoid crowds altogether, but you just want to be smart about it. You want to avoid someone who is hacking, someone who knows they’re sick, and just be intelligent about your exposure.

I also advise patients to avoid raw or undercooked meat, fish, eggs, that sort of thing, but fruits and vegetables appear to be safe.

Jamie DePolo: Do you have to worry about washing them?

Dr. Wojciechowski: Yeah, I usually do recommend that people wash them. It’s good for getting rid of bacteria and that sort of thing, but it’s also probably a good idea because a lot of these fruits and veggies have pesticides on them as well. It’s a good habit to get into.

Jamie DePolo: I have a very specific question about hand washing and hand sanitizers. I know [hand sanitizers are] used everywhere, and I’ve also read some studies that say they don’t really do a much better job than washing your hands. So is that something that somebody who’s in chemo should… obviously they should be washing their hands a lot, but is hand sanitizer a benefit for those folks?

Dr. Wojciechowski: So, washing your hands with soap is the best thing. I think hand sanitizer is really for convenience. So if you’re not in front of a sink 24 hours a day, you do the hand sanitizer. I think it’s better than nothing, but it’s not as good as really getting a good wash with soap.

Jamie DePolo: And one last question to wrap up. When somebody completes their course of chemotherapy, how long does it take before their white blood cells sort of bounce back, or come back up to normal levels?

Dr. Wojciechowski: Of course it does vary depending on how long they were on therapy and what drug combination they were on, but I think generally speaking,, by 3 weeks everyone should be in the clear.

Jamie DePolo: Thank you so much! This has been very, very helpful.

Dr. Wojciechowski: My pleasure!

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