Neutrophils: Defenders of your health

When it comes to keeping you safe from bacterial infections, there are no better troops than neutrophils. If you have too few neutrophils, you are said to be neutropenic. Most CLL patients will face the scary prospect of deep seated neutropenia at some point in their disease, especially if they are being treated with immune suppressive therapy.

Stem cell progenitors in your bone marrow produce baby neutrophils and after they have matured sufficiently  they are pushed out into open blood circulation. Prudently, healthy bone marrow holds back reserves of almost-ready neutrophils nicely tucked away in the nooks and crannies of the bone marrow, ready to be released as it becomes necessary.  Once released from the bone marrow these potent infection fighting white blood cells cruise around in the blood, often entering tissues and organs, always on the look out for lurking infectious pathogens.

Unlike killer T-cells neutrophils are not “smart” troops in the sense that they cannot recognize specific markers on pathogens. Instead, they respond by zeroing in on signs of inflammation – a sure sign of some mischief going on  most of the time. Once at the site of inflammation they discharge their “weapons” and the hope is that in the process they kill any bacteria hanging around the area. Think of them as the run-of-the-mill police officers on the beat in the neighborhood. They are the crucial first responders when trouble breaks out, but they are not very highly trained and skilled detectives / criminologists – that role belongs to T-cells.

Neutropenia comes in different flavors. Mild or transient neutropenia is not the end of the world so long as you are careful about avoiding infections. But most oncologists get concerned if you ANC  is lower than 0.5K.  ANC below this threshold puts you in the dangerous territory of severe neutropenia.  Please read our earlier article on lymphocytes to learn more about ANC (absolute neutrophil count), how it is reported on your monthly CBC blood test, how to calculate it if the report does not spell it out.

Development of modern neutrophil growth factors such as Neupogen and Neulasta to reduce and shorten periods of severe neutropenia has saved lives, increased survival statistics, prevented hospitalizations and improved quality of life of many cancer patients. I want you to remember that important point as you read the rest of this article. Growth factors are powerful drugs. Their use may be associated with adverse effects in special circumstances and this article attempts to highlight situations where you may want to think twice before using them. But there is such a thing as throwing out the baby with the bathwater. Please be sure to discuss the pros and cons of Neupogen therapy with your doctors before you make decisions. As always, more is not necessarily better and do use caution before you pester your doctor for more shots or higher doses of Neupogen, just because it makes your monthly CBC look better.

How do Neupogen and Neulasta work?

Neupogen and Neulasta are brand named drugs that use man-made neutrophil growth factor G-CSF (granulocyte colony stimulating factor), mimicking a similar growth factor made by your own body. This growth factor works by giving the bone marrow marching orders to release neutrophils held in reserve in the bone marrow as well as start production of new baby neutrophils. Releasing already minted reserve troops happens quite quickly, often a matter of hours. As you can imagine, it takes longer to start from scratch and make new neutrophils ready for battle.

Neupogen was introduced first into the marketplace, followed by the longer-lasting Neulasta. We talked about “glycosylation”, addition of long strands of sugar molecules to drug molecules in our latest article on Epo. Addition of these sugar strands makes it harder for the body to get rid of the drug, which in turn makes its therapeutic effect last that much longer.  A similar approach was taken to make Neulasta a longer acting drug.  Neupogen shots are often given on a weekly basis, whereas the longer lasting Neulasta may be given only once a month or so. One of the less lovely side effects of these drugs is deep seated bone marrow pain – a consequence of goosing the bone marrow and forcing it to ramp up neutrophil production.

There is another use of Neupogen and Neulasta that you may not be aware of. The same feature of the drug that makes the bone marrow release reserve neutrophils nesting in there also causes flushing out of other cells residing in the bone marrow – of particular importance, the blood stem cells nicely tucked away in the bone marrow niches. A small number of blood stem cells are normally kept in open blood circulation, but the vast majority of them are kept safe within the bone marrow. When stem cell donors donate stem cells for allogeneic transplantations, they are often given one or more shots of Neupogen to increase the number of stem cells in the blood.  There is an almost immediate increase in the number of stem cells circulating in the blood.  This mass exodus of blood stem cells from the bone marrow gradually reverses over time  (matter of several days) as all the cells kicked out of their comfortable homes mill around a bit in blood circulatin but eventually go back home.

Harvesting stem cells in sufficient numbers  from the blood of donors becomes a much bigger challenge without flushing them out of the bone marrow and into open circulation. The same “flushing out” (also called “mobilization”) takes place also to other cell lines that happen to be sheltering in the bone marrow. A neupogen shot kicks out stem cells, reserve neutrophils, lymphocytes - you name it, any cell living in the bone marrow - out into the open.  While this use of Neupogen has been hugely important in controlling neutropenia and  making it easier for stem cell donors to mobilize sufficient numbers of stem cells, I worry that the same effect in CLL patients undergoing chemotherapy may pose unexpected problems. Read on.

Concurrent Use of Campath and Neupogen / Neulasta

Campath (also known as “alemtuzumab”) is a powerful and very valuable monoclonal antibody in our arsenal against CLL. It is one of the few drugs that works in patients with “Bucket C” cytogenetics with the poor prognosis 17p (p53) deletion, as well as those who have become refractory to fludarabine therapy. Chances are pretty good that the majority of CLL patients who have been through several chemotherapy regimens or with high risk disease will have to use this drug at some point or the other in our battle against CLL.

The single biggest drawback of Campath is that is not very specific. This monoclonal antibody targets CD52 marker - a marker carried by B-cells, T-cells, neutrophils and monocytes.  That is just about the whole kit and caboodle of our cellular immune system.  While it kills B-cells (and therefore CLL cells), Campath therapy also leaves patients with dangerously low levels of T-cells - the real “smart” troops of our immune system.  T-cell levels after Campath therapy are at about the same level as advanced AIDS patients and this T-cell depletion lasts for almost a year or more!

Many of you may not be familiar with monocytes.  If neutrophils are first responders to a crisis, think of monocytes as the instant responders.  In neutropenic patients the very first cell line that the bone marrow is able to get out there onto the battle front are monocytes.  Monocytes are the precursors of dendritic cells and macrophages - literally garbage monsters that can eat bacteria and other other pathogens alive.  Dendritic cells are essential for alerting T-cells to the exact nature of the enemy.  Without dendritic cells telling them what to fight, T-cells are blind and unable to mount an effective attack strategy.

So, to sum it all up, Campath kills B-cells, T-cells, neutrophils, monocytes and therefore macrophages and dendritic cells.  Did I forget anything?  Oh yes, a bit off topic, did you guys know that human sperm also carry the CD52 marker?  Someone suggested a long time ago that Campath can be used as a male contraceptive since it leaves you guys shooting blanks.  Frankly, I think it is a little excessive, treating people with Campath rather than giving them condoms.

The other thing you need to know about Campath is that it is a humanized monoclonal antibody.  The good news about that is that the drug lasts for a long time in the body and therefore its therapeutic effects last for several months or more before last traces of it are gotten rid of.  The bad news is also that it lasts for a long time in the body.  During the many months while it lingers in your blood, it is busy killing B-cells.  But equally likely, it is also killing neutrophils, T-cells, monocytes etc.  That is why immune suppression due to Campath therapy is so deep and long-lasting.

Here is the million dollar question: is there something that can be done to improve the odds in our favor and give patients an improved level of immune protection while they are undergoing Campath therapy? Preventing neutropenia sounds like a good thing to do.  How about giving patients Neupogen / Neulasta shots at the same time as they are getting Campath therapy?  Sounds good, right?  Not!

Leukemia. 2005 Apr 28; [Epub ahead of print]

Filgrastim(Neupogen) and alemtuzumab (Campath-1H) for refractory chronic lymphocytic leukemia.

Lin TS, Flinn IW, Lucas MS, Porcu P, Sickler J, Moran ME, Lucas DM, Heerema NA, Grever MR, Byrd JC.

The Division of Hematology-Oncology, The Ohio State University, Columbus, OH.

Alemtuzumab (anti-CD52; Campath-1H) is effective in fludarabine-refractory chronic lymphocytic leukemia (CLL), but is associated with infection and early onset neutropenia. To reduce toxicity, filgrastim (G-CSF) was administered concurrently with alemtuzumab. In total, 14 CLL patients (median age 59) with a median of 3.5 prior regimens (range 1-12) received i.v. alemtuzumab, stepped up from 3 to 30 mg the first week, then 30 mg thrice weekly for 12 weeks. Filgrastim (Neupogen) 5 mug/kg was administered daily 5 days before and throughout alemtuzumab therapy. Six patients developed cytomegalovirus (CMV) reactivation 3-6 weeks into treatment; six patients developed fever, three neutropenia, and one pneumonia. The patient with CMV pneumonia died; ganciclovir cleared CMV in the other patients. Five patients developed early neutropenia (weeks 2-5). Four patients developed delayed neutropenia (weeks 10-13) unassociated with CMV reactivation. Nine patients ceased therapy because of infectious and hematologic toxicity. Five partial responses were noted, all in patients with lymph nodes >5 cm, lasting a median of 6.5 months (range 5-13). Filgrastim and alemtuzumab were given concurrently with manageable infusion toxicity and clinical activity, but the efficacy of this regimen was limited by delayed neutropenia of unclear etiology and CMV reactivation. Filgrastrim (Neupogen) should not be administered prophylactically during alemtuzumab therapy outside clinical trials.

PMID: 15858611

This was a small study, only 14 patients, but has highly credible authors supporting the startling conclusions highlighted above.

  • None of the patients were chemo naïve. But they were not exactly basket cases either, just your average, been-around-the-block-a-few-times CLL patients. While the patient number was small, the results were dramatic enough to justify pretty solid conclusions.
  • A whopping 11 out of 14 patients developed grade 3-4 thrombocytopenia and / or anemia. If you are not familiar with the grading classification, grade3 is pretty darned serious and grade 4 is even more so.
  • Six of the 14 patients developed full-blown CMV (cytomegalovirus) reactivation, and one of these patients died in hospital in spite of all efforts to contain the infection. As you should know by now, CMV activation is one of the most common opportunistic infections to watch for in Campath therapy. This trial of combining G-CSF with Campath was aimed mostly at controlling opportunistic infections, a task at which it failed spectacularly.
  • Nine out of the 14 original patient cohort discontinued this therapy, and given the results above I am sure none of us are surprised at this very high drop-out rate.
  • There were two important positive observations. Two of five patients with the feared 17p (p53) deletion, achieved a partial response. A similarly high response rate was noted in 5 out of 11 patients (46%) with lymph nodes greater than 5 cm. Typically, Campath does not work well with large lymph nodes, defined as larger than 5 cm.

The researchers were surprisingly blunt in their assessment: Filgrastrim (G-CSF: Neupogen, Neulasta) should not be administered prophylactically during alemtuzumab (Campath) therapy outside clinical trials. In other words, don’t attempt to do this on your own!

What is going on here?

This is how I see it, even though the researchers involved did not connect the dots quite as explicitly as I am about to.  Campath kills all cells that carry the CD52 marker: T-cells, B-cells (CLL cells), neutrophils, monocytes (therefore macrophoages and dendritic cells).  It has a hard time killing any of these cells if they are hidden safely away in large lymph nodes or deep within the bone marrow.

What happens when Neupogen is given concurrently with Campath?  All those nicely hidden “reserve troops” of neutrophils, T-cells, monocytes are flushed out of the bone marrow and into open blood circulation, so many hapless victims to be mowed down by Campath. As any good general knows, it is important to keep fighting troops in reserve; throwing everything he has into an unwinnable fight is the surest way to lose the whole war.  A more prudent strategy would be to keep the reserves safe where they are, live to fight another day.

The take home message?  While neutropenia is a very important part of the immune suppression associated with Campath, it may not be a good idea to try to do an end run around it by giving Neupogen / Neulasta shots concurrently with the Campath therapy.  Not only would this not reduce neutropenia and immune suppression, it might make things worse:  neutropenia and immune suppression may become deeper and longer lasting if all the reserve troops are killed off as well.

What makes this a very complicated question is the fact that Campath lasts for a long time in the body- several months at least. How long are there trace amounts of Campath lurking around  in the patient’s blood, enough to kill any neutrophil or T-cell that pokes its head out of the bone marrow?  I do not know the answer to that question.  Frankly, I am surprised more reports have not followed up this interesting lead about risk factors of concurrent use of Campath and Neupogen / Neulasta.

On the bright side, I speculate that the better than expected response in patients with bulky disease in this study is due to the Neupogen flushing out CLL cells out of the bulky lymph nodes  and therefore making it easier for Campath to kill them. Normally Campath is not able to shrink bulky lymph nodes since it is not able to kill CLL cells tucked away in the lymph nodes.

Concurrent Use of Chemotherapy with Neupogen / Neulasta

Powerful chemotherapy combinations such as FCR and its analogs have revolutionized how we treat CLL patients.  It is not an exaggeration to say they have added years to the life expectancy of our guys.  But there is no denying that they also have serious adverse effect profiles.  For example, FCR is contra-indicated for elderly CLL patients with decreased bone marrow reserve.

What exactly does  “bone marrow reserve” mean?  As we said above, majority of blood stem cells live in the bone marrow.  As we age, the total number of blood stem cells we have available gradually decrease over time - unavoidable ravages of time.  At any given time, a few of these blood stem cells may cruise the blood circulation for a while before going back home to their comfortable niches in the bone marrow where they are more secure and better protected.

Old fashioned chemotherapy drugs such as fludarabine and cyclophosphamide are not exactly friendly to stem cells.  Any blood stem cells caught out in the open blood circulation are fair game, likely to get killed by these and similar  chemotherapy drugs.  But it is a little harder to kill stem cells hidden away in the nooks and crannies of the bone marrow.  I am sure you can see how elderly patients with reduced numbers of stem cells to begin with can hardly afford to have more of them killed by chemo.  What happens when there are too few blood stem cells left?  Since these are the cells that create all other blood cells (red blood cells, platelets, neutrophils etc), lack of sufficient stem cells leaves patients with tough choices: transfusion dependency for the rest of their lives, or an allogeneic stem cell transplant to replace the dead stem cells with new healthy ones from a matched donor.

Where does this leave us when we consider Neupogen / Neulasta shots administered at the same time as fludarabine and cyclophosphamide infusions?  Fortunately, neither F nor C last very long in the human body.  And Rituxan is a very targeted monoclonal antibody, killing only mature B-cells that display the Cd20 marker.  So, if Neupogen or Neulasta is given well past the time when F and C have been excreted out of the body, I would think there should be no problem similar to the Campath + Neupogen scenario we saw above.

But how many patients get Neupogen shots on the same day they are also scheduled to get fludarabine or  cyclophosphamide, because it works better for every one’s schedule and convenience?  And if this done, are we adding to the risk of precious blood stem cells getting flushed out into open blood circulation where they are more readily killed by the toxicity of fludarabine or cyclophosphamide?  Especially in older patients with limited numbers of stem cells, is it prudent to withhold use of Neupogen or Neulasta for couple of weeks before and after latest round of F and C, to limit this potential damage to blood stem cells?

Frankly, I have not seen this potential risk addressed or highlighted in any professional articles.  Unlike the concurrent use of  Campath + Neupogen identified by the OSU researchers, this potential risk of using Neupogen concurrent with chemotherapy has not been addressed elsewhere.  You have to judge for yourself the likelihood that I may be right.  In any case, prudence is the better part of valor they say.  Why not wait for a few days at least after your F and C infusion before you get your Neupogen shot?  I am just saying.

Neutrophils on High Alert

Neupogen and Neulasta shots not only increase the numbers of neutrophils in the blood, they also increase the aggressiveness of the neutrophils.  Think of them as cops on high alert, looking for trouble and only too eager  to shoot-to-kill.  This aspect of Neupogen-boosted neutrophils can be used to our advantage.

For example, combination of Neupogen + Rituxan is likely to work better than just Rituxan alone.  Since Rituxan cannot do a whole lot of CLL cell killing by itself and needs an assist from the immune system, it makes sense that increased numbers of neutrophils will help and having these neutrophils goosed to maximum performance is even better. I remember pitching this concept to Dr. Mike Keating and Dr. Tom Kipps early in my CLL career.  I am happy to report they followed up the suggestion.  A variation on the theme, M. D. Anderson chose to use GM-CSF (granulocyte and macrophage colony stimulating factor; trade name “Leukine”) as the growth factor of choice, along with Rituxan in their clinical trial.  Makes sense, this growth factor increases production and aggressiveness of neutrophils as well as macrophages.  Reports out of M. D. Anderson suggest this approach has met with some success and in fact they recommend it as the therapy of choice for elderly patients with limited stem cell reserve.  (Be sure to note, this is GM-CSF in combination with Rituxan.  No chemotherapy drugs involved that can kill blood stem cells; Rituxan is the monoclonal of choice, therefore no risk of killing all other immune system cells as in the  case of Campath).

Neutrophils on Rampage

While it is a good idea to have cops motivated, willing and able to apprehend criminals, no one wants over-zealous officers shooting first and then asking questions.  As we pointed out in the section above, Neupogen induced and newly minted neutrophils are excellent partners for Rituxan targeted CLL cells.  But as we also point out in the early parts of this review, neutrophils are not really smart troops.  They are not very good at figuring things out for themselves, the way T-cells are.

Basically, neutrophils like to listen for tell-tale signals of inflammation - often a sign of something wrong, criminal elements at work and causing mayhem.  Once they pick the scent of inflammation, they zero in on that spot and start shooting.  Here is where the Keystone-Cops analogy comes in.  Once they reach what they think is the crime scene, neutrophils shoot off their weapons in all directions, hoping to kill the bad guys.  But in the process they can also do a lot of damage to surrounding healthy tissue - collateral damage of an over-zealous and not very smart bunch of defenders with itchy trigger fingers.

It has been known for some time that in some vulnerable patients Neupogen can cause lung damage.  The scenario is easy to imagine.  Some slight infection or  inflammation in the lungs - a common thing in ill patients - precipitates the whole avalanche.  A few Neupogen-goosed neutrophils latch on to the signals of inflammation in the lungs and zero in.  In the process of shooting off their weapons they may cause a lot more damage to lung tissue; which in turn sets off even more pronounced signals of alarm and  inflammation; which draws even more neutrophils-on-steroids to the melee.  You get the picture.  The abstract below reports how this can quickly get out of control - even become fatal.  You can read the full text of the article by clicking on the link.

Bone Marrow Transplant. 2005 Aug;36(3):245-50.

Respiratory status deterioration during G-CSF-induced neutropenia recovery.

Karlin L, Darmon M, Thiéry G, Ciroldi M, de Miranda S, Lefebvre A, Schlemmer B, Azoulay E.

1Medical Intensive Care Unit, Saint-Louis Teaching Hospital and Paris 7 University, Assistance Publique, Hôpitaux de Paris, Paris, France.

Exacerbation of prior pulmonary involvement may occur during neutropenia recovery. Granulocyte colony-stimulating factor (G-CSF)-related pulmonary toxicity has been documented in cancer patients, and experimental models suggest a role for G-CSF in acute lung injury during neutropenia recovery. We reviewed 20 cases of noncardiac acute respiratory failure during G-CSF-induced neutropenia recovery. Half the patients had received hematopoietic stem cell transplants. All patients experienced pulmonary infiltrates during neutropenia followed by respiratory status deterioration coinciding with neutropenia recovery. Neutropenia duration was 10 (4-22) days, and time between respiratory symptoms and the first day with more than 1000 leukocytes/mm3 was 1 (-0.5 to 2) day. Of the 20 patients, 16 received invasive or noninvasive mechanical ventilation, including 14 patients with acute respiratory distress syndrome (ARDS). Five patients died, with refractory ARDS. In patients with pulmonary infiltrates during neutropenia, G-CSF-induced neutropenia recovery carries a risk of respiratory status deterioration with acute lung injury or ARDS. Clinicians must maintain a high index of suspicion for this diagnosis, which requires eliminating another cause of acute respiratory failure, G-CSF discontinuation and ICU transfer for early supportive management including diagnostic confirmation and noninvasive mechanical ventilation.

PMID: 15937498

Is this risk of  acute respiratory syndrome (ARDS) limited to ill cancer patients?  It might surprise you to know that it is not.  As we mentioned above, healthy stem cell donors are given Neupogen shots in order to flush out (“mobilize”) more stem cells for harvesting from their blood.  As you would expect, this administration of Neupogen would also increase the numbers and aggressiveness of neutrophils - after all, that is the main function of this growth factor.  The abstract below points out that a small percentage of these stem cell donors may also be at risk of Neupogen induced lung injury.  Who knew.

Haematologica. 2005 Mar;90(3):ECR10.

Acute lung Injury in a healthy donor during mobilization of peripheral blood stem cells using granulocyte-colony stimulating factor alone.
Arimura K, Inoue H, Kukita T, Matsushita K, Akimot M, Kawamata N, Yamaguchi A, Kawada H, Ozak A, Arima N, Te C.

Department of Hematology and Immunology, Kagoshima University Hospital, Sakuragaoka 8-35-1, Kagoshima, 890-8520, Japan.

Granulocyte-colony stimulating factor (G-CSF), a hematopoietic growth factor, is widely used to accelerate recovery from neutropenia after severe chemotherapy, both decreasing the risk of infection and mobilizing peripheral blood stem cells. Adverse effects occur with G-CSF use in approximately 30% of cases, comprised predominantly of bone pain, headache, and general fatigue. Pulmonary toxicity is very rare. Here, we describe a healthy donor for allogeneic hematopoietic stem cell transplantation who developed acute lung injury (ALI) after 4 days of G-CSF administration. Among the serum cytokines examined, only Interleukin (IL)-1beta level was elevated in this case. As a high level of IL-1beta was detected at the onset of ALI, on day 4 after G-CSF administration, and decreased to below the level of detection on day 11, it is possible in a certain part that IL-1beta was involved in the onset of G-CSF-related ALI in the present case. Granulocyte-colony stimulating factor (G-CSF) is commonly administered to healthy donors to mobilize peripheral blood stem cells (PBSC) for allogeneic hematopoietic stem cell transplantation (allo-HSCT). Adverse events from G-CSF use in healthy donors have been described in approximately 30% of cases, and are comprised predominantly of bone pain, headache, and general fatigue. Pulmonary complications caused by G-CSF include cough, dyspnea, and interstitial or alveolar pulmonary edema with mild-to-severe deterioration of blood oxygen level. Few cases of acute respiratory distress syndrome (ARDS) following G-CSF administration have been reported. The present report describes a healthy donor for allo-HSCT with acute lung injury (ALI) after 4 days of G-CSF administration. The cytokine-related mechanisms of G-CSF administration that contribute to ALI are discussed.

PMID: 15753051

Last Words

This is a complex and important subject and I want to make sure my message is not garbled.

  • Growth factors such a Neupogen, Neulasta, Leukine (GM-CSF) are true life savers.  For the first time, clinicians have tools with which to control severe neutropenia.  Longer life expectancies of many cancer patients are due to better control of neutropenia and therefore avoidance of fatal infections.
  • But once again, these growth factors are potent weapons to be used with caution.  Getting more shots of Neupogen than is clinically indicate just so that you are happy with your blood counts is foolish and dangerous.
  • Equally foolish would be to throw away the baby with the bathwater. If your doctor suggests you need a Neupogen shot to address severe neutropenia, you are well advised to listen carefully; and discuss the pros and cons with him.
  • I am particularly concerned about the lack of discussion among the experts on concurrent use of Neupogen with Campath as well as chemotherapy agents of known toxicity to stem cells.  That last bit, the potential risk of concurrent use of Neupogen with chemotherapy is just  me trying to connect the dots.  It is up to you whether you consider that a credible risk assessment - or not.

I wonder how many of you remember a patient called Kurt Grayson.  I gather he was quite a Hollywood star as well.  He was my friend.  Kurt believed in the combination of chlorambucil and Neupogen.  I am afraid he belonged to the “more is better” school of thought when it came to Neupogen shots.  Eventually, he died of Neupogen induced acute lung injury, ARDS.  As I said, what you don’t know can easily kill you in this complex disease.