Hairy cell leukaemia is a rare type of blood cancer that requires careful treatment decisions based on each patient’s symptoms and disease progression. While the condition develops slowly and may not need immediate treatment in all cases, modern therapies have helped many people achieve long periods without symptoms and maintain a good quality of life.

Understanding Treatment Goals and Options for Hairy Cell Leukaemia

When someone receives a diagnosis of hairy cell leukaemia, a rare form of blood cancer affecting white blood cells called B lymphocytes, understanding the treatment path ahead becomes essential. This condition gets its name from the hair-like projections visible on cancer cells when examined under a microscope. Unlike many other cancers, hairy cell leukaemia often grows very slowly, which means that not every person diagnosed will need treatment right away.^[1]

The primary goals of treatment focus on controlling symptoms, restoring normal blood cell counts, and helping patients maintain their quality of life. Treatment decisions depend on several factors including blood count levels, the size of the spleen, whether infections occur frequently, and how the disease affects daily activities. Some patients may only need monitoring for months or even years before any treatment becomes necessary, while others require immediate intervention to address severe symptoms or dangerous blood count levels.^[4]

Medical organisations have established standard treatments that work well for most patients with this disease. At the same time, researchers continue exploring new therapies through clinical trials, which are carefully controlled research studies testing whether new treatments are safe and effective. These trials offer hope for improved outcomes, especially for patients whose disease returns after initial treatment or who do not respond well to standard approaches.^[3]

Standard Treatments for Hairy Cell Leukaemia

The backbone of hairy cell leukaemia treatment involves chemotherapy, which uses special drugs to destroy cancer cells. However, the chemotherapy used for this disease differs from the intensive treatments often associated with other cancers. The most commonly used drugs belong to a group called purine nucleoside analogues, and they have proven remarkably effective at controlling this specific type of leukaemia.^[12]

Cladribine Treatment

Cladribine, also known by the abbreviation CDA, stands as one of the most effective treatments for hairy cell leukaemia. This drug works by interfering with how cancer cells divide and grow, ultimately leading to their death. Most patients receive cladribine as an injection just under the skin once daily for five consecutive days. Some treatment centres may give it as a continuous infusion into a vein over seven days, while others use alternative schedules such as two-hour infusions for five days or weekly doses for six weeks.^[12]

What makes cladribine particularly appealing is that most people need only one course of treatment. This single course can lead to what doctors call a complete remission, meaning that all signs and symptoms of the disease disappear and blood counts return to normal. Studies show that between 85 and 90 percent of people with hairy cell leukaemia achieve complete remission after cladribine treatment. About half of these patients remain in remission for ten years or longer without needing additional treatment.^[9]

During the days and weeks following cladribine treatment, patients may experience side effects. The most significant concern is that the drug temporarily reduces all types of blood cells, not just the cancer cells. This means the body becomes more vulnerable to infections, may bruise or bleed more easily, and patients often feel extremely tired. The white blood cell count, which helps fight infections, may drop to very low levels. For this reason, patients need close monitoring during this period, and some may need to take antibiotics or antiviral medications to prevent infections while their immune system recovers.^[7]

Pentostatin Treatment

Pentostatin represents another highly effective purine nucleoside analogue used to treat hairy cell leukaemia. Unlike cladribine, which is given as a short course, pentostatin is administered into a vein every two weeks. Treatment continues until the leukaemia is under control or all signs of disease disappear. The total length of pentostatin treatment varies from person to person depending on how well the disease responds, but generally lasts between three to six months.^[12]

Pentostatin works similarly to cladribine by targeting the cancer cells’ ability to survive and multiply. The side effects are also similar, with temporary drops in blood cell counts being the primary concern. Some patients may develop fever, fatigue, nausea, or skin rashes. The choice between cladribine and pentostatin often depends on the treatment centre’s experience, the patient’s other health conditions, and sometimes the patient’s preference regarding treatment schedule.^[4]

Other Standard Treatment Options

When hairy cell leukaemia returns after initial treatment or if the first treatment does not work well enough, doctors may recommend additional therapies. One option involves repeating treatment with cladribine or pentostatin, which often works well even in these situations. Another approach combines chemotherapy with a type of targeted therapy called rituximab.^[17]

Rituximab is a monoclonal antibody, a laboratory-made protein that attaches to specific markers on the surface of cancer cells. When rituximab binds to these markers, it helps the immune system recognise and destroy the cancer cells. Rituximab may be used alone or in combination with chemotherapy drugs. This combination approach sometimes works better than chemotherapy alone, especially for patients whose disease has come back.^[17]

In some cases, doctors may recommend a different chemotherapy drug called bendamustine, particularly for patients whose disease has relapsed after standard treatments. Bendamustine is often given together with rituximab. This combination has shown promising results in controlling disease that has not responded to or has returned after initial treatment with cladribine or pentostatin.^[12]

Surgical removal of the spleen, a procedure called splenectomy, was once commonly used to treat hairy cell leukaemia before effective chemotherapy became available. Today, this surgery is rarely needed because chemotherapy works so well. However, splenectomy might still be considered in unusual situations, such as when the spleen becomes extremely enlarged and causes severe symptoms, or when a patient cannot receive chemotherapy for some reason.^[4]

Innovative Treatments Being Tested in Clinical Trials

Research into new treatments for hairy cell leukaemia continues to advance, offering hope for even better outcomes in the future. Clinical trials test these promising approaches in carefully designed studies that follow strict safety guidelines. These trials typically progress through different phases, each with specific goals and questions to answer.^[3]

BRAF Inhibitors

One of the most exciting developments in hairy cell leukaemia research involves understanding the genetic changes that cause the disease. Scientists discovered that more than 90 percent of patients with hairy cell leukaemia have a specific change, or mutation, in a gene called BRAF. This gene normally helps control how cells grow and divide. The mutation, known as BRAF V600E, causes cells to grow out of control and become cancerous.^[6]

This discovery led to the development of drugs called BRAF inhibitors that specifically block the abnormal protein produced by the mutated gene. Two BRAF inhibitors, vemurafenib and dabrafenib, have been tested in clinical trials for hairy cell leukaemia. These drugs work differently from traditional chemotherapy because they target a specific molecular problem in the cancer cells rather than affecting all rapidly dividing cells in the body.^[17]

Clinical trials have shown that BRAF inhibitors can be effective, especially for patients whose disease has returned after chemotherapy or who have the variant form of hairy cell leukaemia that does not respond well to standard treatments. In these trials, some patients experienced improvement in their blood counts and reduction in spleen size. The drugs are typically taken as pills daily, making them more convenient than intravenous chemotherapy for some patients.^[17]

BRAF inhibitors may be used alone or in combination with other drugs. Some trials have tested vemurafenib or dabrafenib together with rituximab, or dabrafenib with another targeted drug called trametinib. These combination approaches aim to improve effectiveness and potentially reduce the chance of the disease developing resistance to treatment.^[17]

Side effects of BRAF inhibitors differ from those of chemotherapy. Patients may experience skin rashes, joint pain, fatigue, fever, or sensitivity to sunlight. Some people develop other skin problems such as thickening of the skin or small skin growths. These side effects are generally manageable, and doctors monitor patients closely during treatment to address any problems that arise.^[17]

Other Targeted Therapies

Another drug being studied in clinical trials is ibrutinib, which belongs to a class of medications called BTK inhibitors. BTK stands for Bruton’s tyrosine kinase, a protein that plays an important role in the survival and growth of B cells, including the abnormal B cells in hairy cell leukaemia. By blocking BTK, ibrutinib can help slow down or stop the growth of cancer cells.^[17]

Ibrutinib is taken as a daily pill, and clinical trials have tested its effectiveness in patients with hairy cell leukaemia, particularly those whose disease has returned after other treatments. Early results have shown that some patients respond to this drug, with improvements in blood counts and reduction in disease burden. Research continues to determine the best ways to use ibrutinib, whether alone or in combination with other treatments.^[17]

Understanding Clinical Trial Phases

Clinical trials testing new treatments for hairy cell leukaemia progress through several phases. Phase I trials focus primarily on safety, testing different doses of a new drug to find out how much can be given safely and what side effects occur. These trials usually involve small numbers of patients who have not responded to standard treatments.^[3]

Phase II trials examine whether a treatment actually works against the disease. These studies involve more patients and aim to determine whether the new treatment shrinks tumours, improves blood counts, reduces symptoms, or achieves other beneficial effects. Researchers also continue to monitor side effects and gather more information about the drug’s safety profile.^[3]

Phase III trials compare a new treatment directly with the current standard treatment. These are usually large studies involving hundreds of patients. Participants are randomly assigned to receive either the new treatment or the standard treatment, allowing researchers to determine whether the new approach is better, worse, or about the same as existing options. Phase III trials provide the strongest evidence about whether a new treatment should become part of standard care.^[3]

Clinical trials for hairy cell leukaemia are conducted at medical centres around the world, including locations in the United States, Europe, and other regions. Not every patient is eligible for every trial. Eligibility depends on factors such as whether the patient has received previous treatment, how well the disease responded to prior therapies, blood count levels, and other health conditions. Patients interested in participating in a clinical trial should discuss the options with their doctor, who can help determine whether a trial might be appropriate and available.^[3]

Most common treatment methods

• Chemotherapy with purine nucleoside analogues
  • Cladribine given as injections under the skin daily for five days, or as a continuous seven-day infusion into a vein, representing the most effective single treatment course
  • Pentostatin administered into a vein every two weeks for three to six months until the disease is controlled
  • Bendamustine used for patients whose disease has relapsed, often combined with rituximab
• Targeted antibody therapy
  • Rituximab, a monoclonal antibody that attaches to markers on cancer cells and helps the immune system destroy them
  • Used alone or in combination with chemotherapy drugs like cladribine or bendamustine
  • Particularly helpful for patients whose disease has returned after initial treatment
• BRAF inhibitors (in clinical trials)
  • Vemurafenib and dabrafenib, oral drugs that block the abnormal BRAF protein found in most hairy cell leukaemia cases
  • Tested alone or with rituximab or trametinib
  • Especially studied for relapsed disease or variant hairy cell leukaemia
• Other targeted therapies (in clinical trials)
  • Ibrutinib, a BTK inhibitor taken as a daily pill that blocks proteins involved in cancer cell survival
  • Being tested in patients whose disease has returned after other treatments
• Active surveillance
  • Close monitoring without immediate treatment for patients without symptoms or serious blood count problems
  • Regular check-ups every three to six months to track blood counts and watch for symptoms
  • Treatment begins only when specific indicators suggest it would be beneficial

Managing Side Effects and Supporting Recovery

Treatment for hairy cell leukaemia can cause side effects that vary depending on which drugs are used and how each person’s body responds. The most significant concern with chemotherapy drugs like cladribine and pentostatin is the temporary reduction in all types of blood cells. When white blood cells drop to low levels, the body cannot fight infections as effectively. When red blood cells decrease, patients may feel tired and weak. Low platelet counts can lead to easy bruising or bleeding problems.^[4]

To protect patients during this vulnerable period, doctors may prescribe antibiotics to prevent bacterial infections or antiviral medications to guard against viral illnesses. Patients receive instructions about when to contact their care team, such as if they develop a fever, notice unusual bleeding, or feel increasingly unwell. Blood counts are monitored regularly through simple blood tests, and most people see their counts gradually improve over several weeks to months as their bone marrow recovers and begins producing healthy cells again.^[4]

Other side effects of chemotherapy may include fatigue, nausea, skin rashes, or temporary hair thinning (though significant hair loss is uncommon with the drugs used for hairy cell leukaemia). Most side effects can be managed with supportive care and medications. The care team works closely with patients to monitor symptoms, provide treatments to ease discomfort, and ensure the safest possible recovery.^[12]

Active Surveillance: When Watching and Waiting Makes Sense

Because hairy cell leukaemia often develops very slowly, many patients do not need treatment immediately after diagnosis. Instead, they enter a period called active surveillance or watchful waiting. This does not mean doing nothing; rather, it involves careful monitoring without starting medication until treatment becomes necessary.^[4]

During active surveillance, patients visit their doctor regularly, typically every three to six months. At each visit, the care team checks blood counts through simple blood tests, asks about any new symptoms, and performs a physical examination to feel whether the spleen or liver has enlarged. This regular monitoring allows doctors to detect any changes early and recommend treatment if the disease begins to cause problems.^[4]

The decision to start treatment is based on specific criteria. Treatment usually becomes necessary if blood counts drop too low and cause symptoms, if the spleen grows very large and causes discomfort, if frequent or serious infections occur, or if other concerning changes develop. Some patients remain on active surveillance for years without needing treatment, while others may need to start therapy sooner. The individual pattern of disease progression determines the right timing for each person.^[15]

Living with Hairy Cell Leukaemia and Follow-Up Care

For most people with hairy cell leukaemia, treatment leads to excellent results. Many patients achieve complete remission and can return to their normal activities. However, the disease can return months or years later in some people, a situation called relapse. For this reason, ongoing follow-up care remains important even after successful treatment.^[9]

Follow-up visits typically occur every few months initially, then may be spaced further apart as time passes and the patient remains well. During these visits, doctors check blood counts and ask about any symptoms. If the disease returns, treatment can be repeated and is often effective again. Many patients who experience relapse respond well to another course of the same treatment they received initially, or to a different approach if needed.^[4]

Life expectancy for people with hairy cell leukaemia is often similar to that of the general population when the disease is properly treated and monitored. Most people can maintain good quality of life, continue working, and participate in their usual activities. Staying healthy through good nutrition, regular exercise, and avoiding infections when possible all contribute to overall wellbeing.^[9]

Patients and their families may find it helpful to connect with others who have experienced hairy cell leukaemia. Support groups, whether in-person or online, provide opportunities to share experiences, ask questions, and learn from others who understand the journey. Patient organisations dedicated to leukaemia and blood cancers also offer educational resources, information about the latest research, and connections to expert medical centres.^[18]