Waldenstrom’s macroglobulinemia that has returned after treatment or stopped responding to therapy presents a significant challenge, but modern medicine offers a range of treatment approaches that can help control symptoms and slow disease progression, with ongoing research bringing new hope for patients facing this difficult situation.

Navigating Treatment When the Disease Returns

When Waldenstrom’s macroglobulinemia comes back after a period of remission, or when it doesn’t respond well to initial treatment, patients and their doctors must carefully plan the next steps. The term relapsed describes disease that reappears or begins growing again after a period when it was under control. The term refractory refers to situations where the cancer cells continue growing despite treatment, or when the positive effects of treatment don’t last very long.^[1] This situation requires thoughtful decision-making, taking into account how long the previous remission lasted, what treatments were used before, the patient’s age and overall health, and whether certain side effects appeared during earlier therapies.

For many patients whose disease has relapsed or become refractory, additional treatment approaches can successfully provide new periods of remission. The choice of which therapy to use next depends on several important factors. Doctors consider how much time passed since the last treatment, whether the patient could be eligible for stem cell transplantation, and which specific medications were used previously.^[1] Some treatments that worked well before may be used again, while others might be tried for the first time. The goal is always to find the most effective option while minimizing the burden of side effects on the patient’s quality of life.

Understanding the biological characteristics of the disease has become increasingly important in selecting treatments. Scientists have identified specific genetic changes that occur in Waldenstrom’s macroglobulinemia, including mutations in genes called MYD88 and CXCR4. These discoveries have played a significant role in developing new treatments and helping doctors choose the most appropriate therapy for each patient.^[7] The presence or absence of these mutations can influence how well certain drugs work, making genetic testing an increasingly valuable tool in treatment planning.

Standard Treatment Options for Relapsed or Refractory Disease

When Waldenstrom’s macroglobulinemia returns or doesn’t respond to initial therapy, several established treatment approaches are available. One important category is chemoimmunotherapy, which combines chemotherapy drugs that kill cancer cells with immunotherapy drugs that help the immune system fight the disease.^[7] This combination approach takes advantage of two different ways of attacking the cancer at the same time.

A commonly used chemoimmunotherapy regimen combines dexamethasone, rituximab, and cyclophosphamide. This combination has proven highly effective in the relapsed setting. In studies involving patients with relapsed or refractory Waldenstrom’s macroglobulinemia, this combination achieved an overall response rate of 87% after six complete treatment cycles. This included a 4% very good partial response rate, 64% partial response rate, and 19% minor response rate.^[7] These numbers mean that the vast majority of patients experienced some degree of disease control, though the depth of response varied.

Another important chemoimmunotherapy option combines bendamustine with rituximab, often abbreviated as benda-R. Rituximab is a monoclonal antibody, which means it’s a laboratory-made protein that can recognize and attach to specific markers on cancer cells, helping the immune system destroy them. Bendamustine is a chemotherapy drug that damages the DNA inside cancer cells, preventing them from multiplying. In one retrospective analysis involving 111 patients with relapsed or refractory Waldenstrom’s macroglobulinemia, the bendamustine-rituximab combination achieved a major response rate of 74%. Another study of 71 patients with relapsed or refractory disease reported an overall response rate of 80.2% and a major response rate of 74.6%.^[7]

Bruton’s tyrosine kinase inhibitors, or BTKis, represent another major category of treatment for relapsed or refractory Waldenstrom’s macroglobulinemia. These drugs work by blocking a specific enzyme called Bruton’s tyrosine kinase, which cancer cells need to survive and multiply. Ibrutinib was the first drug in this class specifically approved by the U.S. Food and Drug Administration for Waldenstrom’s macroglobulinemia in 2015.^[9] Other BTK inhibitors used in treating this disease include acalabrutinib and zanubrutinib.^[4] These medications are typically taken as pills, which can be more convenient than intravenous infusions, though they must be taken continuously to maintain their effect.

Proteasome inhibitors form another important class of drugs available for relapsed or refractory disease. These medications work by blocking the proteasome, a cellular structure that breaks down proteins. When the proteasome is blocked, abnormal proteins build up inside cancer cells, eventually causing the cells to die. Bortezomib is a commonly used proteasome inhibitor for Waldenstrom’s macroglobulinemia, sometimes given in combination with rituximab and occasionally with dexamethasone added.^[4] Carfilzomib and ixazomib are other proteasome inhibitors that may be used in treating this disease.^[9]

For some select patients, high-dose chemotherapy followed by stem cell transplantation may be considered. This intensive treatment approach involves collecting the patient’s own stem cells (called autologous transplant) or receiving stem cells from a donor (called allogeneic transplant) after receiving very high doses of chemotherapy.^[1] This approach is not suitable for everyone and is typically reserved for younger, healthier patients with aggressive disease. The high-dose chemotherapy is meant to eliminate as many cancer cells as possible, while the stem cell transplant helps restore the bone marrow’s ability to produce healthy blood cells.

Another established drug for relapsed or refractory Waldenstrom’s macroglobulinemia is everolimus, which is marketed under the brand name Afinitor. Additionally, ofatumumab, known by the brand name Arzerra, may be used for patients who cannot tolerate rituximab.^[1] Ofatumumab is another monoclonal antibody that works similarly to rituximab but targets a slightly different part of the same protein on cancer cells, which may be helpful when patients have developed resistance or intolerance to rituximab.

The chemotherapy drugs bendamustine, fludarabine, cyclophosphamide, chlorambucil, and cladribine may be used individually or in various combinations, often together with targeted therapy drugs or corticosteroids such as dexamethasone or prednisone.^[4] Corticosteroids help reduce inflammation and can make chemotherapy more effective, though they come with their own side effects including increased blood sugar, mood changes, and weakened bones with long-term use.

Other medication combinations that doctors may recommend include cyclophosphamide, dexamethasone and rituximab (abbreviated as DRC); bortezomib and rituximab with or without dexamethasone; CVP which combines cyclophosphamide, vincristine and prednisone; R-CVP which adds rituximab to CVP; thalidomide combined with rituximab; and CHOP which combines cyclophosphamide, doxorubicin, vincristine and prednisone.^[4] The choice among these options depends on individual patient factors, previous treatments, and how quickly the disease needs to be controlled.

Some patients with Waldenstrom’s macroglobulinemia develop a condition called hyperviscosity syndrome, where the blood becomes too thick due to high levels of IgM protein. This can cause serious problems including bleeding, vision difficulties, and nervous system issues. For these patients, a procedure called plasmapheresis or plasma exchange may be necessary.^[4] This procedure involves removing blood from the patient, separating out the plasma that contains the excess IgM protein, replacing it with a substitute fluid, and returning the blood to the patient. While this provides rapid relief from hyperviscosity symptoms, it’s a temporary measure that must be combined with other treatments that address the underlying disease.

Promising Therapies Being Tested in Clinical Trials

Clinical research is actively exploring new treatment options for patients with relapsed or refractory Waldenstrom’s macroglobulinemia. These studies are organized into different phases that serve specific purposes. Phase I trials focus primarily on safety, determining the appropriate dose and identifying side effects. Phase II trials examine whether the treatment is effective against the disease. Phase III trials compare the new treatment against current standard options to see if it offers advantages.^[3]

One of the most promising drugs currently being studied for relapsed or refractory Waldenstrom’s macroglobulinemia is venetoclax. This medication belongs to a class called BCL2 inhibitors, which work by blocking a protein called BCL2 that helps cancer cells avoid normal cell death. Many types of cancer cells, including those in Waldenstrom’s macroglobulinemia, produce too much BCL2, which allows them to survive when they should die. By blocking this protein, venetoclax can trigger the natural death process in cancer cells.^[5]

A phase II trial tested venetoclax monotherapy, given at a dose of 800 mg daily for two years, in 32 patients with relapsed or refractory Waldenstrom’s macroglobulinemia. Notably, 16 of these patients had previously been treated with BTK inhibitors. The trial showed impressive results, with an overall response rate of 84%, a major response rate of 81%, and a minor response rate of 19%. With a median follow-up of 33 months, the treatment demonstrated sustained effectiveness.^[4] These results were particularly encouraging because the treatment worked even in patients whose disease had progressed despite BTK inhibitor therapy, which is often a challenging situation.

A larger multicenter retrospective analysis examined venetoclax treatment in 76 patients with relapsed or refractory Waldenstrom’s macroglobulinemia across nine U.S. medical centers. The patients had a median age of 66 years and had received a median of three prior lines of treatment. Genetic testing showed that 94% had MYD88 mutations, 40% had CXCR4 mutations, and 22% had TP53 mutations. The study found that 82% of patients had been previously treated with a covalent BTK inhibitor and 71% had received an alkylating agent. Despite this heavy pretreatment, venetoclax achieved an overall response rate of 70% and a major response rate of 63%. The median progression-free survival was 28.5 months, and the 2-year progression-free survival rate was 57%. The median overall survival had not been reached, and the 2-year overall survival rate was 82%.^[5] These results confirm that venetoclax can be highly effective even in heavily pretreated patients.

Several other innovative drugs are being investigated in clinical trials for relapsed or refractory Waldenstrom’s macroglobulinemia. Acalabrutinib, another BTK inhibitor, is being studied both alone and in combination with other drugs.^[9] Daratumumab, which is a monoclonal antibody that targets a protein called CD38 on cancer cells, is also under investigation. Tirabrutinib represents another BTK inhibitor being tested in clinical studies.^[9]

Researchers are also exploring entirely new approaches to treating Waldenstrom’s macroglobulinemia. One particularly innovative approach is CAR T-cell therapy, which stands for chimeric antigen receptor T-cell therapy. This treatment involves collecting a patient’s own immune cells called T-cells, genetically modifying them in a laboratory to recognize and attack cancer cells, and then infusing them back into the patient. A specific CAR T-cell therapy called 19(T2)28z1XX, which targets a protein called CD19 on lymphoma cells, is being studied for Waldenstrom’s macroglobulinemia.^[9] While this approach is still experimental, it represents the cutting edge of cancer immunotherapy.

Another drug being studied is ulocuplumab, though its specific mechanism of action in Waldenstrom’s macroglobulinemia requires further investigation through ongoing trials.^[9] Clinical trials are being conducted at medical centers in the United States, Europe, and other regions around the world. Patients interested in participating in clinical trials should discuss eligibility criteria with their healthcare team, as these criteria vary depending on the specific study and may include factors such as previous treatments received, disease characteristics, and overall health status.

Most common treatment methods

• Chemoimmunotherapy
  • Dexamethasone, rituximab, and cyclophosphamide combination achieving 87% overall response rate in relapsed or refractory disease
  • Bendamustine combined with rituximab (benda-R) with major response rates of approximately 74%
  • CHOP regimen combining cyclophosphamide, doxorubicin, vincristine, and prednisone
  • CVP or R-CVP regimens using cyclophosphamide, vincristine, and prednisone with or without rituximab
• Bruton’s Tyrosine Kinase Inhibitors (BTKis)
  • Ibrutinib, the first FDA-approved therapy specifically for Waldenstrom’s macroglobulinemia
  • Acalabrutinib and zanubrutinib as alternative BTK inhibitors
  • Taken as continuous oral therapy to block enzyme needed for cancer cell survival
• Proteasome Inhibitors
  • Bortezomib alone or combined with rituximab and dexamethasone
  • Carfilzomib and ixazomib as alternative proteasome inhibitors
  • Work by blocking protein breakdown in cancer cells, causing cell death
• BCL2 Inhibitors
  • Venetoclax showing 70% overall response rate in heavily pretreated patients
  • Median progression-free survival of 28.5 months in large retrospective study
  • Effective even after BTK inhibitor failure
• Monoclonal Antibodies
  • Rituximab targeting CD20 protein on cancer cells
  • Ofatumumab for patients intolerant to rituximab
  • Daratumumab under investigation in clinical trials
• Stem Cell Transplantation
  • High-dose chemotherapy followed by autologous stem cell transplant using patient’s own cells
  • Allogeneic transplant using donor stem cells for select patients
  • Reserved for younger, healthier patients with aggressive disease
• Supportive Procedures
  • Plasmapheresis for rapid relief of hyperviscosity syndrome
  • Removes excess IgM protein from blood temporarily
  • Combined with definitive treatments addressing underlying disease
• Investigational Therapies
  • CAR T-cell therapy (19(T2)28z1XX) targeting CD19 on cancer cells
  • Novel BTK inhibitors including tirabrutinib and acalabrutinib
  • Combination approaches tested in Phase I, II, and III clinical trials