The MastAttack 107: The Layperson’s Guide to Understanding Mast Cell Diseases, Part 83

96. Why are cancer drugs used to treat mast cell disease?

Disclaimer: The following post was written by me in my capacity as a subject matter expert in mast cell disease and author of MastAttack. This is not work product of my position as a Senior Scientist for a large research organization. All below statements are attributable directly to me in my role as author of MastAttack and are in no way attributable to my employer. Information presented here is publicly available and includes no confidential information learned in my capacity as a Senior Scientist for my employer.

  • There are a number of medications used to treat cancers that are also used to treat mast cell disease. Some of those medications are old school chemotherapies, some are newer, targeted chemotherapies, and some help to control the immune system.
  • In mastocytosis, the body makes too many mast cells. If the bone marrow makes way, way too many mast cells, and those mast cells don’t function correctly, the mast cells can act like cancer cells. This can cause the mastocytosis to behave like cancer.
  • Systemic mastocytosis has several subtypes. The least serious forms do not act like cancer.
  • Indolent systemic mastocytosis (ISM) is the least severe form of systemic mastocytosis. ISM has a normal lifespan. While patients with ISM are at risk of dying for anaphylaxis, an important distinction is that patients with ISM do not die because the mast cell disease acts like a cancer. ISM does not act like cancer.
  • Smoldering systemic mastocytosis (SSM) is a moderately serious form of systemic mastocytosis. SSM can shorten lifespan. In SSM, the body is starting to make lots more mast cells than it should. Those mast cells can affect how organs function. SSM acts like an early cancer.
  • SSM requires treatment to stop it from becoming a more serious form of mastocytosis called aggressive systemic mastocytosis (ASM) that acts like a serious cancer. The treatments used to manage SSM are also used in some cancer patients to help fight cancer. These include meds that affect your immune system, like interferon; newer targeted therapies and chemos, like tyrosine kinase inhibitors; and older chemo drugs, like cladribine.
  • Aggressive systemic mastocytosis (ASM) is a serious form of systemic mastocytosis. ASM shortens lifespan significantly. In ASM, the body makes way too many mast cells. The bone marrow churns out so many mast cells into the bloodstream and then the abnormal mast cells get stuffed into various organs. The mast cells cause organ damage and can cause organ failure. ASM is often referred to as being malignant because it behaves just like a cancer. It is also treated like a cancer.
  • As mentioned above, interferon is a therapy that can affect how the immune system works. Interferon is sometimes used for ASM but it is less commonly used in ASM than in SSM. ASM patients need more aggressive treatment. Newer targeted therapies like tyrosine kinase inhibitors and multitarget kinase inhibitors are frequently used in ASM. Some of these newer therapies are FDA approved for treating some ASM patients. Cladribine and hydroxyurea are still common treatments for ASM.
  • Mast cell leukemia (MCL) is the most serious form of systemic mastocytosis. MCL greatly reduces lifespan. MCL causes production of an unbelievable number of mast cells. There are so many mast cells that they cannot all get stuffed into organs like ASM. This means that while there are lots of mast cells in the organs in MCL patients, there are so many mast cells like that there are still tons of them in the bloodstream. This leads to rapid organ failure, leading to death. Mast cell leukemia is cancer. It is treated like cancer with newer therapies like tyrosine kinase inhibitors and multitarget kinase inhibitors, as well as hydroxyurea or cladribine in some cases. As in ASM, some of the newer therapies are FDA approved to treat mast cell leukemia.
  • Sometimes patients with systemic mastocytosis develop a second blood disorder. This is called systemic mastocytosis with associated hematologic disease. Sometimes this second blood disorder is a form of cancer, like chronic myeloid leukemia. In these instances, the other blood disorder would be treated using cancer medications.
  • Mast cell sarcoma (MCS) is a cancerous form of systemic mastocytosis. Patients with MCS rapidly develop MCL and are treated as described above.
  • None of the therapies I mentioned here are indicated for cutaneous mastocytosis. Cutaneous mastocytosis does not behave like a cancer and is not treated like one.
  • In recent years, two other forms of mast cell disease have been described: mast cell activation syndrome and monoclonal mast cell activation syndrome.
  • Monoclonal mast cell activation syndrome (MMAS) is often considered to be a “pre-SM”. It is treated like indolent systemic mastocytosis and does not behave like a cancer.
  • Mast cell activation syndrome (MCAS) is not know to be an early form of SM. Many people live with MCAS for decades without ever developing SM.
  • Despite the fact that mast cell activation syndrome, monoclonal mast cell activation syndrome, and indolent systemic mastocytosis do not behave like cancer, cancer therapies are sometimes used in these patients. They are used when other therapies have failed and their symptoms are still poorly controlled. Generally, they are used when persistent mast cell activation becomes life threatening. In some instances, they may be used when a patient’s symptoms are not life threatening but are very disabling and cause a poor quality of life. In these cases, the patient and their provider make the assessment that they are able to assume the risk of using these medications.
  • There is very little data on the use of chemo and targeted therapies in patients with MCAS, MMAS and ISM, and no cancer therapies are FDA approved for these conditions. However, use of cancer meds for nonmalignant conditions is not that unusual. It is pretty common in autoimmune disease where lower doses of chemotherapy drugs can be effective in controlling the disease. Basically, the idea is that if we know that these therapies help forms of mast cell disease that behave like cancers then it might help those forms that don’t act like cancer.
  • On a number of occasions, I have seen patients discussing the dangers around certain cancer meds that are sometimes used to treat mast cell disease. In particular, I have seen comments that newer targeted therapies “do not kill cells”, “cannot cause organ damage”, and are “harmless.” This is completely untrue. There are thousands of articles on the side effects and complications of all of the meds I have described here. None of them are harmless. Patients need to understand the risks associated with these therapies.
  • I would like to add a note about something sort of related. Xolair is an anti-IgE medication that is used by many mast cell patients. It is a subcutaneous injection and is administered in a healthcare setting. Patients are required to stay in the office for a little while after the shots are given to be sure that they don’t have a bad reaction. Because the patient is monitored in the office after the shot, the provider’s office will bill insurance for the observation period. The old billing code for this often comes up as “chemotherapy observation” because the same code was used for patients who needed monitoring after chemo. This means that patients may see “chemo” on the explanation of benefits from their insurance company. This does not mean that they received chemo. Xolair is NOT chemotherapy. It’s just a quirk of the medical billing. There is now a new code for post injection observation for meds that are not chemo but not everyone has caught up to it. Just figured I would mention this as people ask about it from time to time.

The MastAttack 107: The Layperson’s Guide to Understanding Mast Cell Diseases, Part 81

94. How are mast cells involved in cancer?

  • Mast cells are very involved in cancer biology. They are frequently found in tumors. Tumors can trick mast cells into doing things they need to stay alive, like make blood vessels to supply the tumor with blood, and tissue remodeling, to push aside the healthy tissue and make room for the tumor.
  • Cancer is mast cell activating. All cancers. This is because cancers often trick the body into doing things that help the cancer and not the body, like I just described above. Having cancer frequently causes allergy symptoms because of mast cell activation.
  • Cancer can also cause the body to make more mast cells than normal, a condition called mast cell hyperplasia. This can happen because the body is trying to fight off the cancer with more immune cells or because it has been tricked by the cancer to make more mast cells to help the cancer.
  • Please note that mast cell hyperplasia is NOT the same as mastocytosis. Mast cell hyperplasia is too many healthy mast cells that function normally. Mastocytosis is too many aberrant mast cells that do not function normally. Cancer does not cause mastocytosis.
  • Long term inflammation increases future risk of cancer at the site of inflammation. This applies almost universally. Mast cells participate significantly in inflammation so they can contribute to the risk of cancer. For example, patients with long term colon inflammation, which may be caused by mast cells, are at increased risk of colon cancer.
  • Patients with mastocytosis have increased risk of developing cancer, especially those with systemic mastocytosis. As many as 40% of patients with systemic mastocytosis develop another blood disorder with too many broken cells. Frequently, the other blood disorder is a blood cancer like chronic myelogenous leukemia.
  • It is not yet known if mast cell activation carries an increased risk of developing cancer.
  • Two forms of systemic mastocytosis are cancerous, mast cell leukemia and mast cell sarcoma. These are both extremely rare and it is extremely rare for a person with a history of mast cell disease to develop either of these conditions.

For further reading, please visit the following post:

The MastAttack 107: The Layperson’s Guide to Understanding Mast Cell Diseases, Part 48

Mast cells in the GI tract: How many is too many? (Part Three)

The MastAttack 107: The Layperson’s Guide to Understanding Mast Cell Diseases, Part 48

59. Is systemic mastocytosis a form of cancer? Why do some papers say the life expectancy for systemic mastocytosis patients is much shorter?

Systemic mastocytosis is a term that different people use in different ways, often without defining them for the audience. This can lead to some confusion.

In its broadest sense, systemic mastocytosis is actually a disease category rather than one specific diagnosis. The subtypes of systemic mastocytosis are indolent systemic mastocytosis (ISM), smoldering systemic mastocytosis (SSM), systemic mastocytosis with associated hematologic disease (SM-AHD), aggressive systemic mastocytosis (ASM), and mast cell leukemia (MCL).

When patients talk about systemic mastocytosis without specifying which diagnosis, they almost always mean indolent systemic mastocytosis (ISM), the most common form of SM. ISM is benign and has a normal life expectancy. But when providers and researchers talk about systemic mastocytosis, they usually mean the disease category that includes all of these diagnoses.

I just recently explained in another post what a neoplasm is. It is essentially when the body grows something that doesn’t belong there, like extra cells or a tumor. Cancers are neoplasms but not all neoplasms are cancerous. Indolent systemic mastocytosis is not cancerous. Even without taking drugs to kill off lots of mast cells, the prognosis is excellent with a normal life span. However, aggressive systemic mastocytosis and mast cell leukemia are considered cancerous. Without taking drugs to kill off mast cells, the body would be unable to cope with the huge number of mast cells and the damage they cause. Smoldering systemic mastocytosis is sort of a bridge between ISM, which is benign, and ASM, which is not.

If you are not aware that research papers usually use the term systemic mastocytosis to mean all forms of systemic mastocytosis and not just indolent systemic mastocytosis (ISM), it is easy to get confused and misunderstand what is being said. There was a paper published in 2009 that discussed expected survival for the various forms of systemic mastocytosis. It provides a very jarring statistic for patients who may not understand the context. This study found that many patients with systemic mastocytosis died 3-5 years after diagnosis.

Let’s pull this apart. We know there are five forms of SM: indolent SM, the most common form, which usually has a normal life span; smoldering SM, which usually has a shortened life span; aggressive SM, which can have a very shortened life span; mast cell leukemia, which has a very shortened life span; and SM with an associated hematologic disorder, which may have a shortened life span. When you average the life expectancies for a mixed group of patients with these various diagnoses, it shows that overall, SM patients are more likely to die 3-5 years after diagnosis when compared to healthy people of the same age.

Additionally, a lot of the patients in this study group were older and died of causes unrelated to systemic mastocytosis. However, because they were part of the study, their deaths of unrelated causes were still included in this data.

Let’s recap: in a research paper, the term systemic mastocytosis includes forms of SM that are malignant and can really shorten your life expectancy as well as forms that are benign and do not shorten your life expectancy. When you average the life expectancies of all of these forms together, it looks like patients are more likely to die 3-5 years after diagnosis. A bunch of other papers then used the data from this study in 2009 without explaining the details behind it. However, most patients with SM have normal life spans.

For more detailed information, please visit these posts:

The Provider Primer Series: Diagnosis and natural history of systemic mastocytosis (ISM, SSM, ASM)

The Provider Primer Series: Natural history of SM-AHD, MCL and MCS

The question I get asked the most

Whether or not SM is cancer is, by far, the question I get asked the most.  Because I get asked so often, I have done a lot of digging on this topic in the last few months.  Here’s what I found.

On the surface, from a biological point of view, SM looks like cancer.  It is characterized by excessive, improper cell growth.  It can cause organ infiltration and damage.  Over 90% of patients have a mutation in the CKIT gene, which is a proto-oncogene.  A proto-oncogene is a gene that becomes an oncogene when mutated.  An oncogene is a gene that contributes to cancer.  CKIT mutations can lead to gastrointestinal stromal tumors (GIST), melanoma, acute myeloid leukemia and, of course, mast cell disease.  So if SM has unregulated cell growth and a mutation in a proto-oncogene, that makes it cancer, right?
The World Health Organization (WHO), an organization I generally consider to know what they are doing, says it doesn’t.  To find out exactly why, I talked to a pathologist familiar with mast cell disease.  This is what she said:
“All cancers are neoplasms, but not all neoplastic cells are cancerous.  It is cancerous when the cells grow out of control.  In mastocytosis, even if you do nothing (meaning take no medications designed to kill off the mast cells), most of the time, the prognosis is very good because the cells are not growing that much.  Not like a cancer.  The other thing is when the cells invade other organs and the bloodstream and damage the organs.  When it is widespread and damaging, it is malignant.”
The majority of people with systemic mastocytosis have indolent disease, for which the life expectancy is normal, usually without any kind of therapy to kill off mast cells.  So if we follow the guidelines laid out above, SM is not cancer.   It is a myeloproliferative neoplasm (MPN.)
I know some people with ASM identify as having cancer.  ASM has a lot more features we typically associate with cancer, so I think that’s fine.  And MCL, obviously, is leukemia.
There is some terminology that gets thrown around incorrectly and I think it scares people who don’t understand that the wrong terms are being used.  One of them is chemo.  People with more aggressive types of mast cell disease may need chemo drugs.  People sometimes use the term incorrectly to reference more common treatments.  If you’re a rookie, I can see how you might get scared thinking that lots of people with indolent disease are on chemo.
Another term is compassionate use.  Compassionate use is the use of an experimental drug outside of a clinical trial.  It is generally allowed only when the person has no other treatment options and is gravely ill.  I have seen some people use it when discussing patient assistance programs, in which a pharmaceutical company will distribute a drug to a patient at a significant discount or at no cost.  They are not the same thing.
In the last few months, I have noticed that some people with SM will tell people that they have a “rare kind of leukemia.”  This is not accurate.  With the obvious exception of MCL, mast cell disease is not leukemia.  SM is a blood disorder. 
I think that part of why some people with mast cell disease say they have leukemia is because they want the sort of empathy given to cancer patients.  I understand that.  I wrote a whole post about how I hate when people say, “At least it’s not cancer.”  But it’s important to remember that cancer has two entities: the medical, biological aspect of the disease, and the social construct.  When you have ISM and you tell someone you have leukemia, their first thought is that you could die from it.  Mast cell disease is scary enough with scaring everyone around you extra with misinformation. 
I know that it’s frustrating that people know what cancer is and they probably don’t know what mast cell disease is.  And to be clear, I’m not talking about an offhand comment you make to some stranger asking you why you have a port at the grocery store to get them to go away.  I’m talking about the people who are actually in your life.  (I’m also obviously not referring to the SM-AHNMD people, who may very well have leukemia in addition to SM.)  If our mission is to educate people, stuff like this matters.  The words we use  matter.  A lot.  
I’m aware that this post is probably going to make some people angry, and that’s fine.  You can feel however you want to feel.  But I’m getting enough questions about this from people who are really worried, so I feel it’s important to set the record straight.