The National Comprehensive Cancer Network® (NCCN®) – an alliance of leading cancer centers – announced the publication of new NCCN Guidelines® for histiocytosis. These clinical practice guidelines provide the latest evidence and expert-consensus for diagnosing and treating the three most common forms of histiocytosis in adults: Langerhans cell histiocytosis (LCH), Erdheim-Chester Disease (ECD,) and Rosai Dorfman Disease (RDD). Although the guidelines are focused on adult patients, there may be insight for pediatric physicians as well. The Guidelines are listed as “histiocytic neoplasms” and can be found on NCCN’s website.
You can find consensus guidelines for the diagnosis and clinical management of Erdheim-Chester disease, here. It is encouraged that you share this with your physicians for reference.
On November 1st, 2022, Memorial Sloan Kettering Cancer Center (MSK) announced that the U.S. Food and Drug Administration (FDA) has approved the oral MEK inhibitor drug cobimetinib (Cotellic®) for the treatment of adult patients with the family of blood diseases known as histiocytic neoplasms (HN). These diseases include Erdheim-Chester disease, Rosai-Dorfman disease, and Langerhans cell histiocytosis. Cobimetinib is an oral inhibitor of MEK1 and MEK2, currently approved to treat melanoma. Gratitude and congratulations to the Principal Investigator of this study, Dr. Eli Diamond, neuro-oncologist and neurologist at MSK and Chair of the Scientific Committee for the Histiocytosis Association. We applaud the efforts of Dr. Diamond and the entire study team for this tremendous advancement. Read more here.
The diagnosis of ECD can be challenging and requires review of the biopsy of a tumor specimen in light of clinical and radiographic findings.
The classic diagnostic finding of ECD is abnormal imaging of the bones around the knee on a CT scan, PET scan, MRI, or a technetium bone scan. A PET CT scan (head to toes) is the preferred imaging study as it also allows to search for other sites of disease more accurately as compared with other radiographic tests. A biopsy of one of the affected sites from ECD using a needle or through surgery is usually conducted and reviewed by an expert pathologist under the microscope for features suggestive of ECD. One of these characteristics is the presence of foamy (bubbly) histiocytes with signs of inflammation.
A special test called immunohistochemistry is undertaken by using stains (dyes) that check for certain markers (antigens) in the tumor sample. The stains are called as “positive” if the tumor cells bind to the dye and are visible under the microscope, and negative if they do not. Altogether, the pattern of “positive” and “negative” stains help pathologists make a diagnosis from a biopsy sample. ECD cells are positive for the “markers” (stains) CD68 and factor XIIIa , and negative for CD1a. Langerhans cell histiocytosis, by contrast, is positive for CD1a. In addition, testing for mutations of the BRAF and other genes through special tests called as next generation sequencing (NGS) studies on the biopsy specimen or blood may be undertaken to help aid in the diagnosis or treatment. There are many hospitals, laboratories, or companies that perform NGS, and it is recommended to discuss with your doctor about which one to use for your case . In cases where the classic knee bone involvement or characteristic staining on biopsy is not present (seen less than 10% of the time), presence of a mutation in combination with other features mentioned above may lead to a diagnosis of ECD.
Baseline evaluation and testing
Once the diagnosis of ECD is made, detailed history, physical exam, and tests are undertaken to determine the extent of the disease, i.e., determining what organs are involved with the disease:
- History: A detailed health history is undertaken including the onset and duration of symptoms, past illnesses, health and lifestyle habits, and medical conditions experienced by the family
- Physical examination: Includes a detailed exam of the body to search for signs of ECD. A specialized neurological exam may also be undertaken to evaluate if ECD has affected the brain and the nervous system, and includes testing for reflexes, coordination, muscle strength, sensations, and memory
- Blood tests:
- Complete blood count with differential – to check for hemoglobin, platelets, and different types of white blood cells
- Chemistries, including kidney and liver function tests: To evaluate the function of kidney and liver
- C-reactive protein (CRP)- a marker of inflammation which can be elevated in ECD
- Urine and serum osmolality, water deprivation test- to check if the ECD has affected the pituitary gland hormone that helps in concentration of urine is being secreted adequately
- Other hormone tests – to assess whether ECD has affected endocrine organs like the pituitary gland, thyroid gland, or the adrenal glands
- BRAF and other genetic mutation testing- to check for BRAF-V600E and other mutations in the blood
- Tests on biopsy specimen:
- Immunohistiochemistry: This test uses various types of dyes to find markers that can help in the diagnosis of ECD and differentiate it from other diseases. At times, BRAF-mutation testing can also be achieved relatively quickly using immunohistochemistry methods
- Molecular testing for BRAF and other mutations: This test involves testing the tissue for changes in the BRAF gene, especially the BRAF-V600E mutation, as well as other mutations that can be driving the ECD (KRAS, NRAS, etc.). Some of these tests require sending the biopsy sample to a specialized laboratory that can take several days to weeks to result. Knowledge of these mutations can help with the diagnosis and treatment of ECD
- PET (positive emission tomography) scan: To check for tumor cells in the body, a small amount of radioactive sugar is injected into a vein followed by taking pictures in a PET-scanning machine. The disease-causing cells look brighter than surrounding cells due to increased uptake of glucose
- CT (compound tomography) scan: This is an x-ray that takes a number of detailed pictures of various organs and structures within the body, often conducted in combination with a PET scan. Dye may be injected into a vein or taken by mouth to make the images more clear
- Bone scan: This is a type of x-ray that looks for rapidly dividing cells in the bones. A small amount of radioactive material is injected into a vein, collects in any abnormal parts of the bones, and is detected on a scanner
- MRI (magnetic resonance imaging): A special type of scan that used magnetic waves to obtain detail pictures of various body parts. A substance called gadolinium may be injected into a vein to get clearer pictures
- Ultrasound: This is a procedure where sound waves are used to create echoes and collect pictures of organs
- Electrocardiogram: This is a tracking of the heart rate and rhythm
- Echocardiogram: This uses sound waves to provide pictures of the heart in order to evaluate blood flow and heart function
- Bone marrow aspiration and biopsy: This procedure involves suctioning of a small amount of bone marrow and taking a small piece of the bone by inserting a hollow needle in the hip bone
- Specialist examinations: This may include a neurological examination to test ability to walk, muscle testing, coordination, etc.; other specialist visits or specific testing may be recommended by your physician
Staging
In many diseases or cancers, there is the concept of “staging” which refers to the extent or severity of the disease within the body (for example, “stage 4 lung cancer.” There is no standard staging system for ECD. The severity of the disease is determined by how widespread the involvement occurs outside of bone and whether internal organs are affected.
Treatment
General principles of treatment
Most patients with ECD will require treatment at the time of diagnosis. In some patients who do not have any symptoms or any critical organ involvement like brain or heart, it is reasonable to pursue a “wait and watch” strategy for some period of time without treatment. In these cases, close monitoring by a specialist is needed, and may include repeated imaging studies like PET scan or CT scan.
Patients with ECD should have their treatment planned by a team of health care providers who are experts in the disease, including and not limited to the following:
- Cancer specialist (hematologist/oncologist)
- Hormone specialist (endocrinologist)
- Autoimmune disease specialist (rheumatologist)
- Lung specialist (pulmonologist)
- Brain and nervous system specialist (neurologist)
- Skin specialist (dermatologist)
- Heart specialist (cardiologist)
- Nephrologists (Kidney Specialists)
- Ophthalmologist (Eye Specialist)
- Psychologist and supportive care specialist
Treatments available for ECD
The treatment approach to ECD has evolved significantly due to discovery of mutations in the BRAF and other genes, leading to the successful use of targeted therapies in most cases. Treatments for ECD can be divided into two categories- targeted and conventional treatments. Patients may also consider enrolling in a clinical trial if available near them.
Targeted Therapies: Targeted therapies include treatments that attack specific genes or protein in the cancer cells. Targeted therapies are likely required to be taken for a long time, as there is concern that the ECD will recur upon stopping the drug. There are different types of targeted therapies available for ECD:
- BRAF-inhibitors (vemurafenib, dabrafenib, encorafenib): These drugs are typically used when there is presence of the BRAF-V600E mutation in the tumor cells. These drugs are taken by mouth and the dose can vary based on side effects and response to treatment. The common side effects include skin reactions (rash or skin cancer), joint pains, and fatigue. Seeing a skin doctor regularly can help with management of these effects. Other less common but important adverse effect is abnormal heart rhythm or reduced heart function. Some patients on these drugs will get routine electrocardiograms and echocardiograms to monitor the effects on the heart. Some of the side effects may necessitate switching one type to BRAF-inhibitor to another.
- MEK-inhibitors (cobimetinib, trametinib, binimetinib): These drugs are typically used when there is no BRAF-V600E mutation in the tumor cells. These drugs are taken by mouth and the dose can vary based on side effects and response to treatment. Common side effects include skin rash, and patients may need to see a skin doctor for management. These drugs can also reduce the heart function, and sometimes an echocardiogram may be needed to monitor the effects on heart. Another notable side effect is changes in the layer of the tissue in the back of eye that senses light (retina) leading to blurry vision or loss of vision. It may be necessary to get regular eye exams while on treatment with these drugs.
- Other inhibitors – mTOR inhibitors (sirolimus, everolimus), imatinib, sorafenib: These are less commonly used targeted therapies but can occasionally result in disease remission. These drugs are taken by mouth and the dose can vary based on side effects and response to treatment. Side effects with mTOR inhibitors include abnormal cholesterol levels, lung inflammation (pneumonitis), and worsening of diabetes mellitus. Side effects with imatinib and sorafenib include rash, fatigue, and diarrhea.
There are several BRAF inhibitors (vemurafenib, dabrafenib, and encorafenib) and MEK inhibitors (cobimetinib, trametinib, binimetinib, selumetinib). The BRAF inhibitors are given for histiocytosis with the BRAFV600E mutation, and the MEK inhibitors are given in many different instances, including (1) cases of mutations in the MAPK pathway other than BRAFV600E (2) cases where no mutation has been identified and (3) for BRAFV600E mutations as well. In some instances of histiocytosis with BRAFV600E mutation, combined BRAF and MEK inhibitors are given. Which specific inhibitor medication (i.e. cobimetinib versus trametinib) a physician may administer can depend on several factors, such as (1) the amount of evidence that exists for a particular medication for a specific disease or age group (2) the experience of the physician administering a particular medication and (3) possible drug interactions between the inhibitor and an individual’s other medications.
Conventional Treatments:
- Immunotherapy (interferon-alpha, peginterferon-alpha): Interferon was the most commonly used treatment for ECD before the introduction of BRAF and MEK-inhibitor therapies. Interferon is administered as an injection under the skin. Most common side effects that are experienced by the patients include fatigue, joint pain, flu-like symptoms, and depression.
- Chemotherapy (cladribine, cytarabine, vinblastine, methotrexate): These drugs are given through the vein or mouth (methotrexate only). Chemotherapy works by slowing the growth of or killing rapidly dividing tumor cells. These drugs have the potential to weaken the immune system and can lead to infectious complications. Vinblastine can cause damage to the nerves leading to neuropathy, manifesting as numbness, tingling, or pain of fingers and toes. Cladribine can increase the risk of a particular type of pneumonia (pneumocystis pneumonia) so preventative antibiotics may need to be administered alongside.
- Anti-cytokine therapy (anakinra, canakinumab, tocilizumab, infliximab): These treatments work by reducing the inflammation that is generated by tumor cells. Most commonly used drug is anakinra and is given as an injection under the skin. Common side effects include skin rash at the site of injection, headache, and sore throat. Tocilizumab and infliximab are given through the vein. Common side effects of these drugs include headache, nausea, stomach pain, and diarrhea.
- Other treatments (steroids, surgery, radiation): Steroids may be given through the vein or by mouth to reduce inflammation from ECD. The side effects include weight gain, stomach upset, sleep disturbances, and increased blood sugars. Surgery may be used to remove ECD lesions or to reduce the pressure from a large lesion behind the eye. Occasionally, radiation therapy using high energy x-rays or protons may be used to kill tumor cells. The side effects of radiation can depend on the site of radiation and the amount of normal tissue exposed to the radiation.
Monitoring on Treatment
Once treatment is initiated, patients will likely need monitoring for assessing the response to therapy and also management of side effects of treatments. Some of the tests that may be undertaken include:
- Physical exam, including neurological exam
- Skin exams in patients on BRAF- and MEK-inhibitor treatments
- PET scan to check for reduced brightness and size of the tumor sites
- Additional imaging studies (CT, MRI) may be undertaken based on organs involved at diagnosis. Imaging (PET, CT, MRI) is usually repeated every few months and can be variable for each patient
- Blood tests to assess for changes from the disease or the treatments
- Hormone evaluation and treatment with the help of an endocrinologist
Treatment of Relapsed ECD
If the tumor grows back after treatment, it is called as relapsed disease. In such cases, one of the other targeted or conventional treatments than used previously may be utilized. In some cases, a repeat biopsy of tumor cells may be needed for confirmation of diagnosis and mutation testing. If a clinical trial is available, that may be a consideration as well.
Supportive Care
Despite improvement in treatments, patients with ECD struggle with many symptoms such as extreme tiredness, body pain, depressed mood, anxiety, and memory difficulty. In many cases, getting additional input from psychology, supportive/palliative care, psychiatry, and pain specialists may be helpful. Leading a healthy lifestyle (exercise, balanced diet) may help improve some of these symptoms in addition to medications.
Prognosis
The prognosis of ECD has continued to improve with introduction of newer treatments and early diagnosis. That has allowed ECD to become more of a chronic disease; however, at this point it is still considered incurable. It is important for patients to continue to follow up with their healthcare provider to ensure no complications such as second cancers or side effects of treatment develop. If there is development of any new symptoms, it is critical to notify the healthcare team to catch these problems in a timely manner.