Richter’s syndrome is a rare but serious complication of chronic lymphocytic leukaemia, where the disease suddenly transforms into an aggressive form of lymphoma. This transformation requires urgent medical attention and specialised treatment approaches to manage the rapid progression and improve patient outcomes.

Understanding the Challenge of Sudden Transformation

When someone is living with chronic lymphocytic leukaemia, most people understand they are dealing with a slower-growing blood cancer. However, in some cases, the disease can suddenly change into something much more aggressive. This is what doctors call Richter’s syndrome or Richter’s transformation. The main goal of treating this condition is to control the rapidly progressing disease, reduce symptoms, and where possible, achieve remission that might allow for more intensive treatments like stem cell transplantation. Treatment needs to be tailored to each person’s situation, taking into account what type of lymphoma has developed, whether they’ve had previous treatment for leukaemia, and their overall health status.^[1][2]

Richter’s syndrome develops when chronic lymphocytic leukaemia (CLL) rapidly transforms into a high-grade lymphoma. This transformation is not something that happens gradually over time. Instead, patients can become unwell quite suddenly. The most common transformation is into a type of non-Hodgkin lymphoma called diffuse large B-cell lymphoma, which is a fast-growing cancer of the lymphatic system. This occurs in around 90 out of 100 cases of Richter’s syndrome. Less commonly, about 10 out of 100 cases transform into Hodgkin lymphoma instead.^[2][3]

This condition is relatively rare, affecting between 2 and 10 out of every 100 people with chronic lymphocytic leukaemia during the course of their disease. The transformation rate is approximately 0.5 to 1 percent per year. While some studies have reported incident rates ranging from about 1 to 23 percent, more recent data from large databases suggests the transformation rate might be around 0.7 percent. Richter’s syndrome can occur at any time during the course of chronic lymphocytic leukaemia, whether someone has been living with the condition for years or has only recently been diagnosed.^[4][5]

Standard Treatment Approaches

The standard first-line treatment for Richter’s syndrome that has transformed into diffuse large B-cell lymphoma is a chemotherapy regimen known as R-CHOP. This name comes from the initial letters of the drugs used: rituximab, cyclophosphamide, doxorubicin hydrochloride, vincristine sulfate, and prednisone. This combination therapy brings together different mechanisms to attack the cancer cells. Rituximab is a targeted drug that specifically recognises cancer cells, while the chemotherapy drugs work in various ways to stop cancer cells from multiplying. Prednisone is a steroid that helps reduce inflammation and supports the effectiveness of the other drugs.^[5]

Another chemotherapy regimen that is sometimes used is called EPOCH-R, which includes etoposide, prednisone, vincristine, cyclophosphamide, doxorubicin, and rituximab. Both of these regimens involve combining chemotherapy with immunotherapy, which is treatment that helps the body’s immune system fight the cancer. The choice between different chemotherapy regimens depends on several factors, including the patient’s previous treatment history, the specific characteristics of their cancer cells, and their overall health condition.^[5]

Treatment duration typically involves several cycles of chemotherapy, usually administered over a period of several months. Each cycle is followed by a rest period to allow the body to recover before the next treatment. The exact number of cycles depends on how well the cancer responds to treatment and how well the patient tolerates the side effects.^[2]

The side effects of chemotherapy for Richter’s syndrome can be significant. Common side effects include fatigue, nausea and vomiting, hair loss, increased risk of infections due to low white blood cell counts, and mouth sores. The chemotherapy drugs can also affect blood cell production in the bone marrow, leading to anaemia (low red blood cells) and thrombocytopenia (low platelets), which can cause bleeding or bruising. Patients receiving R-CHOP or similar regimens need close monitoring throughout treatment to manage these side effects and adjust treatment if necessary.^[2][5]

For patients who achieve remission with initial chemotherapy, doctors often consider stem cell transplantation as a consolidation treatment. This intensive therapy involves using high doses of chemotherapy to destroy cancer cells, followed by transplantation of healthy stem cells to rebuild the bone marrow. Stem cell transplant is currently the only treatment associated with the potential for long-term survival in Richter’s syndrome. However, not all patients are suitable candidates for transplant, as it requires good overall health and the availability of a suitable donor if an allogeneic (from another person) transplant is planned.^[2][5]

Treatment in Clinical Trials

Because standard chemotherapy alone often does not produce long-lasting remissions, researchers are actively investigating new treatment approaches through clinical trials. One promising area of research involves adding targeted drugs to standard chemotherapy regimens. Scientists at major cancer centres are testing whether combining chemotherapy with drugs like venetoclax can improve outcomes for patients with Richter’s syndrome.^[5][9]

Venetoclax is a targeted drug that works by blocking a protein called BCL-2, which helps cancer cells survive. By blocking this protein, venetoclax can make cancer cells more susceptible to chemotherapy. In one clinical trial conducted at Dana-Farber Cancer Institute, researchers tested a combination of EPOCH-R chemotherapy with venetoclax. The study produced promising rates of complete remissions, although patients did experience significant side effects. Based on these encouraging results, investigators are planning follow-up trials combining R-CHOP with venetoclax to see if this approach can offer better outcomes with more manageable side effects.^[5]

Patients with Richter’s syndrome who have an abnormal p53 protein in their cancer cells tend to become rapidly resistant to chemotherapy agents. The addition of venetoclax aims to restore the cancer’s susceptibility to these drugs, potentially improving treatment effectiveness. These studies represent Phase II clinical trials, where the main goal is to determine how well the treatment works and to continue monitoring safety in a larger group of patients.^[5]

Another exciting area of clinical trial research involves combining different types of targeted therapies. Investigators are currently leading trials that test combinations such as copanlisib with nivolumab, and duvelisib with venetoclax. Copanlisib and duvelisib are both drugs that target a protein called PI3K, which is involved in cancer cell growth and survival. By blocking PI3K, these drugs can help slow down or stop cancer growth. Nivolumab is an immunotherapy drug that works by blocking a protein called PD-1, which helps the immune system recognise and attack cancer cells more effectively. These combination approaches are based on research suggesting that the drugs used together can reinforce each other’s effects, potentially leading to more durable remissions.^[5][9]

For patients who do not achieve remission with standard chemotherapy regimens, another option being explored is CAR T-cell therapy. This is a highly specialised form of immunotherapy that uses genetically modified versions of a patient’s own immune system cells to generate a powerful attack on lymphoma cells. The process involves collecting T-cells (a type of white blood cell) from the patient’s blood, modifying them in a laboratory to express special receptors that can recognise and attack cancer cells, and then infusing the modified cells back into the patient. CAR T-cell therapy has shown promise in treating aggressive lymphomas and is being investigated for use in Richter’s syndrome.^[5][9]

In the United Kingdom, researchers are conducting a trial called the STELLAR trial, which is adding the targeted drug acalabrutinib to standard CHOP-R treatment. Acalabrutinib is a type of drug called a BTK inhibitor, which blocks a protein involved in the growth and survival of certain cancer cells. The trial aims to compare how well people with Richter’s syndrome respond to standard treatment alone versus standard treatment followed by acalabrutinib. Researchers also want to find out how long it takes before the cancer gets worse with each treatment approach. This trial is testing the hypothesis that more people will respond to the combination treatment and that the response will last longer compared to current standard treatment.^[14]

Researchers are also investigating a class of drugs called non-covalent BTK inhibitors and bispecific T-cell engagers. Bispecific T-cell engagers are antibodies designed to bind to both cancer cells and T-cells, bringing them into close contact so that the T-cells can destroy the cancer cells. These innovative therapies are currently being studied in Phase I and Phase II clinical trials for Richter’s syndrome, with the goal of finding more effective and less toxic treatment options.^[9]

Clinical trials for Richter’s syndrome are being conducted at major cancer centres in the United States, including Dana-Farber Cancer Institute and MD Anderson Cancer Center, as well as in Europe. Patient eligibility for these trials depends on several factors, including the type of Richter’s transformation, previous treatments received, genetic characteristics of the cancer cells, and overall health status. Patients interested in participating in clinical trials should discuss this option with their oncology team to determine if they might be suitable candidates for any ongoing studies.^[5][9][14]

Most common treatment methods

• Chemoimmunotherapy combinations
  • R-CHOP regimen containing rituximab, cyclophosphamide, doxorubicin hydrochloride, vincristine sulfate, and prednisone
  • EPOCH-R regimen including etoposide, prednisone, vincristine, cyclophosphamide, doxorubicin, and rituximab
  • Combination of chemotherapy drugs with targeted antibodies like rituximab to attack cancer cells
• Targeted therapy combinations
  • Venetoclax combined with chemotherapy to block BCL-2 protein and make cancer cells more susceptible to treatment
  • PI3K inhibitors such as copanlisib and duvelisib that target proteins involved in cancer cell growth
  • BTK inhibitors like acalabrutinib that block proteins involved in cancer cell survival
• Immunotherapy approaches
  • Nivolumab that blocks PD-1 protein to help the immune system attack cancer cells
  • CAR T-cell therapy using genetically modified immune cells to target and destroy lymphoma cells
  • Bispecific T-cell engagers that bring cancer cells and immune cells together for destruction
• Stem cell transplantation
  • High-dose chemotherapy followed by stem cell transplant to rebuild the bone marrow
  • Currently the only treatment associated with potential for long-term survival
  • Considered for patients who achieve remission with initial treatment