Hairy Cell Leukemia: An Overview for New Patients
History
Hairy Cell Leukemia (HCL) is a rare disease contributing to about 2% of all adult leukemia cases. Cell mutations similar to HCL were first observed as early as 1923 and called leukemic reticuloendotheliosis. In 1958, Dr. Bertha Bouroncle had several patients with these cell mutations and further explored the characterization of this disease. By 1958, this disease was classified as a lymphoproliferative disorder and called hairy cell leukemia. At that time, patients had a survival rate of only four to five years post diagnosis. Fortunately, several clinical trials took place in the 1980’s and various treatments were discovered, the first being interferon alpha. Cladribine and pentostatin were later developed as viable treatments for HCL, achieving a near normal life expectancy for patients with the disease.
Approximately 600 to 800 new cases of HCL are diagnosed in the US every year with men being four times more at risk than women. Even though there is a lower incidence within Asian, Arab and African populations, these populations are commonly underserved. Several environmental factors may also increase risk for getting HCL, such as exposure to pesticides, diesel and ionizing radiation.
Diagnosis
HCL is understood to originate from a mutated B-cell, a common type of white blood cell that protects your body from infection. The mutated cell will start to take on a hairy-like exterior and multiplies throughout the bone marrow, spleen and other parts of the body. Some indicators of HCL include low blood counts, low monocyte counts, enlargement of the spleen and possible infection when diagnosed. Mutated hairy cells may or may not be circulating throughout one’s blood, so the best method of diagnosis is a bone marrow biopsy. Retrieving and staining bone marrow cells can help identify hairy cell mutations, thus most accurately confirming the diagnosis. Additional testing may be useful, such as an ultrasound of the spleen for accurate measurements, or a CT scan to better understand which parts of the body are most affected.
Treatment Criteria
A majority of patients with HCL require immediate treatment, however approximately 10% of patients are on a watch and manage basis. Treatment is usually recommended when hemoglobin, also known as red blood cells, are less than 11 g/dL. Furthermore, a platelet count less than 100,000 uL or an absolute neutrophil count less than 1000/uL may indicate that treatment is required. Lastly, any symptoms related to the enlargement of the spleen are also a concern for treatment.
Blood counts do tend to fluctuate frequently in HCL patients so it is imperative to have a couple of values before deciding on treatment. Treatment is not curative and there are side effects such as increased risk of infections. If a patient is asymptomatic, it may be best to hold off on treatment as there may not be long-term benefits of beginning treatment sooner than necessary.
Cladribine and Pentostatin
The most common chemotherapies used to treat HCL are cladribine and pentostatin, both effective up front and in relapse settings. These drugs are very similar, however, cladribine’s doses are all given upfront over the course of one week, and pentostatin is given as a dose every two weeks. Pentostatin can also be stopped as needed if the patient is recovering from a virus. These treatments are highly effective for classic HCL, with 100% overall response rate upfront and a 70-90% complete response rate.
It is estimated that 40% of patients will experience a relapse in their lifetime. One of the most significant side effects from these chemotherapies is the decreased blood count during the initial stages of treatment which is approximately four weeks. This can lead to immunosuppression, which is a decrease in the number and efficiency of immune system cells or myelosuppression, which is the overall suppression of bone marrow function. If a kidney infection is found, patients could experience neurological toxicities, such as balance problems. The immune system will not normalize until approximately a year post treatment. Overall, there are several side effects with chemotherapy treatments and careful consideration should be taken before choosing these options.
Other Treatments
In 2011, Dr. Farhad Ravandi (MD Anderson Cancer Center in Houston, TX) found that cladribine with the addition of rituximab is highly effective in HCL treatment. Similarly, Dr. Enrico Tiacci (University and Hospital of Perugia in Italy) found that vemurafenib with the addition of rituximab is effective. This combination treatment is unique as it is not chemotherapy based, yet, displays similar results. In 2018, the Federal Drug Administration (FDA) in the U.S. approved moxetumomab pasudotox which was developed by Dr. Robert Kreitman at the National Institutes of Health (NIH). This drug is effective in treating HCL, however, it has a more complex schedule. Moxetumomab pasudotox, marketed as Lumoxiti, is FDA approved in the U.S. for relapsed or refractory disease only, not for patients who are newly diagnosed or have not previously been treated.
Overall, there are many factors for patients and their doctors to consider before choosing a treatment for the patient’s HCL. Whether it is chemotherapy or a pill, all forms of treatment will involve some side effects. It is important for patients to discuss with their doctors and take careful consideration before starting any treatment process.
Complications
There are a number of complications that may arise due to HCL. Whereas a weakened immune system is one of the most prominent concerns, HCL can also put patients at risk for other types of cancers. Specifically, non-melanoma skin cancer is common, so it is vital for HCL patients to visit a dermatologist once a year. Furthermore, it is important to have regularly scheduled scans, such as mammograms and colonoscopies.
HCL patients may also have an increased risk for auto-immune disorders, the most common being palindromic arthritis which can be treated with steroids. Inflammatory arthritis can also develop and if this occurs HCL patients are encouraged to make an appointment with a rheumatologist.
Quality of Life
Survivorship plays a vital factor for HCL patients’ long-term outlook and quality of life. An HCL diagnosis can greatly affect one’s mental health. Family members and friends may constantly try to uplift patients with positive messages, however, these messages can hinder patients from being able to express their emotions and struggles. This is called toxic positivity.
It is important for patients to prioritize their mental health even post treatment. Some patients may consider getting treatment for PTSD due to healthcare trauma. Being diagnosed with cancer can be overwhelming so talking to a professional and finding the right coping mechanisms can greatly improve quality of life.
While there are effective treatments for HCL, survivors can experience long-term effects of the disease, so it is vital for patients, including after treatment is finished or they are in remission, to continue prioritizing their health and focusing on their wellbeing.
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Source Information
An October 10, 2021 webinar presentation and discussion hosted by the Hairy Cell Leukemia Foundation with speaker Dr. Leslie Andritsos served as a major source of information for this blog. Dr. Andritos is a hematologist at the University of New Mexico Comprehensive Cancer Center. She is trained in the treatment of patients with hematological malignancies as well as blood and marrow transplantation. Dr. Andritsos received her undergraduate training at Texas Tech University and attended medical school at the University of Texas Medical Branch in Galveston. Following this, she completed her training in Internal Medicine, Hematology/Oncology, and Blood and Marrow Transplantation at Washington University in St. Louis. Dr. Andritsos is currently a Professor of Internal Medicine in the Division of Hematology/Oncology at the University of New Mexico Comprehensive Cancer Center, a member of the Blood and Marrow Transplant and Cellular Therapies Program, and the Leukemia Research Program of the OSU Comprehensive Cancer Center.
Author Information
We gratefully acknowledge the work of Kuyili Velagapudi, our Spring 2022 Communications Intern. Kuyili is a Public Health and Communication Studies student at The College of New Jersey.