Lymphoma is a type of cancer that originates in the lymphatic system, a network of tissues and organs that help rid the body of toxins, waste, and other unwanted materials. When doctors assess this disease, they use various tests to understand its characteristics and spread. One blood test often included in this evaluation measures a substance called lactate dehydrogenase, or LDH.
What Is Lactate Dehydrogenase (LDH)?
Lactate dehydrogenase is an enzyme found in nearly all living cells, with high concentrations in the heart, liver, kidneys, muscles, and red blood cells.
LDH converts sugar into energy by catalyzing the reaction between pyruvate and lactate, a process active during low oxygen conditions. When cells or tissues are damaged or break down rapidly, they release LDH into the bloodstream. A simple blood test measures these levels, indicating cellular injury or turnover.
The Role of LDH in Lymphoma Diagnosis
Lymphoma involves the rapid proliferation and turnover of abnormal white blood cells, specifically lymphocytes. As these cancer cells grow quickly and break down, they release substantial amounts of LDH into the bloodstream, leading to elevated levels. For example, in Hodgkin lymphoma, Reed-Sternberg cells and surrounding inflammatory cells contribute to this elevation through their metabolic activity and cell breakdown. Elevated LDH can indicate a higher “tumor burden,” meaning the total amount of cancer present.
An LDH test does not diagnose lymphoma on its own. Instead, it serves as one piece of a larger diagnostic puzzle. Doctors consider LDH levels alongside other diagnostic procedures, such as biopsies of affected lymph nodes and imaging scans like PET or CT scans. These combined assessments provide a more complete picture of the disease, guiding further evaluation and treatment decisions.
LDH as a Prognostic Factor
In many types of lymphoma, particularly non-Hodgkin lymphoma, the LDH level at diagnosis helps predict the disease’s course. Higher LDH levels suggest a more aggressive or widespread disease. Studies show a correlation between elevated LDH and a less favorable prognosis. For instance, an LDH level greater than 320 U/L has been associated with a poorer chance of achieving complete remission in certain lymphomas.
LDH is incorporated into prognostic models that estimate disease progression and help plan treatment intensity. One such model is the International Prognostic Index (IPI), which combines several factors, including LDH levels, to stratify patients into different risk groups. Elevated LDH is a risk factor within the IPI, signifying a more challenging disease course and influencing therapeutic choices. This helps tailor treatment strategies.
Monitoring Lymphoma Treatment and Remission
Beyond diagnosis and prognosis, LDH tests monitor treatment response. A decrease in LDH levels during therapy often indicates effective reduction of cancer cells. This decline suggests the lymphoma is responding well. The European Society for Medical Oncology recommends checking LDH levels at specific intervals, such as 3, 6, 12, and 24 months after achieving complete remission.
Conversely, an LDH level that remains high despite treatment, or begins to rise after normalization, can signal inadequate response to therapy. A rising LDH can also suggest relapse, meaning the cancer has returned after remission. While LDH changes are valuable indicators, they are interpreted with imaging studies and clinical assessments for a comprehensive view of disease status and treatment effectiveness.
Other Conditions That Elevate LDH Levels
An elevated LDH level is not exclusively indicative of lymphoma or cancer. LDH is a non-specific marker of tissue damage; many conditions can cause its levels to rise. When cells are injured or destroyed, they release this enzyme. Therefore, a high LDH result requires medical evaluation to determine its specific cause.
Several common non-cancerous conditions can lead to elevated LDH levels. These include heart attack, where damaged heart muscle releases LDH, or liver diseases like hepatitis or cirrhosis. Kidney disease, muscle injuries, and certain types of anemia, especially hemolytic anemia where red blood cells break down prematurely, can also increase LDH. Even strenuous exercise or certain medications can temporarily elevate LDH, highlighting why a single test result is never interpreted in isolation.