Chronic lymphocytic leukemia refractory represents a situation where the disease does not respond to treatment or comes back after an initial response. Understanding when and how to diagnose this condition is important for patients and their healthcare teams as they make decisions about next steps in care.

Introduction: Who Should Undergo Diagnostics

People diagnosed with chronic lymphocytic leukemia may experience periods when their disease seems stable, followed by times when it starts to progress or stops responding to treatment. When someone with CLL finds that their disease has returned after a period of remission, or when their current treatment is no longer controlling the disease, doctors need to perform careful diagnostic evaluations to understand what is happening. This is particularly important for people who are experiencing new or worsening symptoms, or whose routine blood tests show concerning changes.^[1]

Not everyone with CLL will need treatment right away. In fact, many people newly diagnosed with this condition enter what doctors call active surveillance, where the disease is closely watched without starting active treatment. During active surveillance, the healthcare team uses tests and examinations to check whether CLL is progressing or if your condition is getting worse, which might suggest it’s time to begin treatment. However, when disease does progress or return after treatment, more detailed diagnostic work becomes necessary.^[5]

Anyone who previously had CLL under control but now notices swollen lymph nodes in the neck, underarm, stomach, or groin should seek medical evaluation. Similarly, people who feel increasingly tired, develop fever and frequent infections, notice easy bruising or bleeding, experience unexplained weight loss, or have drenching night sweats should contact their healthcare provider promptly. These signs may indicate that the disease is becoming active or that it’s no longer responding to current therapy.^[2]

The window of time between when disease starts to come back and when the next treatment begins represents an important opportunity. During this period, doctors need to perform diagnostic tests to understand the current state of the disease, assess its aggressiveness, and determine the best path forward. This time also allows the healthcare team to optimize the patient’s overall health by addressing infections, updating vaccinations, checking for other health problems, and treating conditions unrelated to CLL that might affect well-being or future treatment options.^[3]

Classic Diagnostic Methods Used to Identify Relapsed or Refractory Disease

When doctors suspect that chronic lymphocytic leukemia has relapsed or is no longer responding to treatment, they begin with a thorough physical examination. During this examination, the healthcare provider carefully checks for swollen lymph nodes in multiple areas of the body, including the neck, underarms, and groin. They also examine the abdomen to see if the spleen has become enlarged, which can be felt as a sense of fullness or discomfort below the ribs. An enlarged spleen often signals that leukemia cells are accumulating in this organ.^[4]

Blood tests form the foundation of diagnosing relapsed or refractory CLL. A complete blood count measures the number of different types of cells in the blood. In CLL that has progressed, doctors typically see an increase in the number of abnormal lymphocytes, which are a type of white blood cell. At the same time, there may be fewer healthy white blood cells, red blood cells, and platelets because the leukemia cells crowd them out of the bone marrow. This crowding can lead to infections because of low normal white blood cells, anemia (feeling tired and weak) from low red blood cells, and easy bruising or bleeding from low platelets.^[2]

Another important blood test looks at the size, shape, and appearance of cells under a microscope. This test, called a peripheral blood smear, allows the laboratory to examine what the blood cells actually look like. In CLL, this test often shows many small, round lymphocytes and sometimes cells called “smudge cells” which are fragile leukemia cells that break apart during preparation of the blood sample.^[2]

Doctors also perform specialized tests that identify specific proteins on the surface of the cancer cells. These proteins, called markers, help confirm the diagnosis of CLL and distinguish it from other blood cancers. They also provide information about how aggressive the leukemia cells might be. This testing is particularly important when disease comes back because the characteristics of the leukemia cells can change over time.^[2]

Laboratory tests look for changes in the cancer cell DNA. Cancer happens when cells develop changes in their genetic material, and certain DNA changes in CLL cells indicate more aggressive disease or resistance to specific treatments. For example, some patients develop mutations in genes called BTK or other related genes, which can cause resistance to certain targeted therapies. Doctors test for these mutations when someone’s disease stops responding to treatment with BTK inhibitors, which are medications that block a protein called Bruton’s tyrosine kinase. Understanding which mutations are present helps doctors choose the most appropriate next treatment.^[1]

Sometimes doctors recommend a bone marrow biopsy and aspiration. During this procedure, a healthcare professional collects cells from inside the bone, usually from the hip bone. The bone marrow is where blood cells are made, and examining these cells under a microscope shows how much of the marrow is filled with leukemia cells. This test is particularly useful when blood counts are low and the reason isn’t clear, or when doctors need to understand how extensively the disease has spread in the bone marrow.^[14]

Imaging tests help doctors see whether leukemia has affected lymph nodes or organs inside the body that cannot be felt during a physical exam. Computed tomography (CT) scans use X-rays to create detailed pictures of the inside of the body. These scans can show enlarged lymph nodes in the chest, abdomen, or pelvis, as well as an enlarged spleen or liver. Imaging becomes especially important when doctors need to understand the full extent of disease burden and how it has changed since the last evaluation.^[14]

When someone’s disease comes back with unusual symptoms or grows much faster than expected, doctors may be concerned about a serious complication called Richter transformation. This happens when CLL transforms into a more aggressive type of lymphoma. To diagnose this transformation, doctors may perform a lymph node biopsy, where they remove a piece of an enlarged lymph node and examine it under a microscope. Special tests on this tissue can confirm whether the cells have changed into a different, more aggressive cancer. This distinction is critically important because the treatment approach differs significantly when transformation has occurred.^[3]

Diagnostics for Clinical Trial Qualification

When someone with relapsed or refractory CLL considers participating in a clinical trial, they undergo additional specific diagnostic tests that serve as standard criteria for enrollment. Clinical trials test new treatments or combinations of treatments, and researchers need to carefully document the characteristics of each participant’s disease to understand how well the experimental therapy works. These qualifying tests ensure that the study includes the right patients and provides reliable information about the treatment being studied.

One key assessment used in clinical trials is measuring measurable residual disease, often abbreviated as MRD. This extremely sensitive test can detect tiny numbers of leukemia cells that remain in the blood or bone marrow even when the disease appears to be in remission by standard tests. MRD testing has become increasingly important in venetoclax-based limited-duration therapy, where treatment is given for a fixed period rather than continuously. There is growing evidence that patients who achieve MRD negativity, meaning no detectable leukemia cells by this sensitive test, tend to have better outcomes. However, researchers are still determining whether MRD status should become a standard measure used in routine clinical practice outside of trials.^[1]

Clinical trials often require detailed genetic testing of the leukemia cells. Researchers want to know whether patients have specific high-risk features such as TP53 aberrations (abnormalities in a gene called TP53), unmutated IGHV status (a characteristic of the immune system genes in the leukemia cells that indicates more aggressive disease), or specific chromosome abnormalities like deletion of part of chromosome 17, written as del(17p). These genetic features help predict how the disease will behave and how it might respond to treatment. Patients with these high-risk characteristics represent a population with significant unmet medical needs, and many clinical trials specifically focus on finding better treatments for them.^[1]

Before enrolling in most clinical trials, patients undergo comprehensive testing to assess their overall health and organ function. Blood tests check kidney function, liver function, and blood cell counts. These baseline measurements help researchers understand whether someone is healthy enough to tolerate the experimental treatment and whether they meet the specific eligibility criteria for the study. Many trials also require performance status assessments, which measure how well someone can carry out daily activities. This evaluation helps ensure that participants can safely undergo the study treatment.^[3]

Clinical trials testing new types of therapies, such as chimeric antigen receptor T-cell therapy (CAR-T) or bispecific antibodies, often require additional specialized tests. For CAR-T cell therapy trials, doctors need to confirm that a patient has enough healthy T cells (a type of immune cell) to collect and modify in the laboratory. They also need to ensure the patient doesn’t have active infections or other conditions that might interfere with the cell collection process or the treatment itself. These cellular therapies represent promising new approaches that have shown significant activity in relapsed and refractory CLL in early studies.^[1]

Trials evaluating sequential use of different treatments need to document what therapies a patient has previously received and how they responded. This history becomes part of the qualifying criteria. For instance, some trials specifically enroll patients whose disease progressed while taking continuous BTK inhibitors, while others focus on people who completed venetoclax-based treatment but later relapsed. Understanding the sequence and outcomes of prior treatments helps researchers determine which patients are most likely to benefit from the new therapy being tested.^[3]

Some trials require patients to undergo imaging studies at specific intervals to measure disease burden precisely. These imaging tests, which might include CT scans, positron emission tomography (PET) scans, or ultrasound examinations, create a baseline picture of where and how much disease is present at the start of the trial. Researchers then repeat these tests at defined time points to see whether the experimental treatment is shrinking lymph nodes, reducing the size of an enlarged spleen, or achieving other measurable improvements. This careful documentation helps determine whether a new treatment is effective.^[3]