Characteristics
Multiple myeloma (MM), also called Kahler’s disease, is a blood cancer that arises from plasma cells in the bone marrow. Plasma cells develop when B-lymphocytes, a type of white blood cells, are activated by an infection. In normal circumstances, these plasma cells produce antibodies (also called immunoglobulins) that help the body attack and kill viruses or bacteria. In MM, plasma cells are transformed into cancerous cells that grow out of control. Instead of producing normal immunoglobulins, MM cells produce high amounts of an abnormal antibody called M-protein.
In MM, a malignant plasma cell clone takes the place of the healthy cells in the bone marrow, causing anaemia. Myeloma patients are also at risk for bone fractures. These arise from 2 mechanisms: a direct destruction of the bones by a plasma cell tumour or a disbalance in osteoblasts and osteoclasts (bone cells) in the bones of patients with myeloma, which leads to increased bone destruction. Finally, the buildup of M protein in the blood or urine of MM patients has the ability to cause kidney damage or damage other organs.
In 2021, 995 patients were diagnosed with MM in Belgium. It is slightly more common in men than in women and the disease mostly affects people above 65 years of age. The exact cause and the risk factors for the development of MM are largely unknown. Interestingly, there seems to be a close link between MM and 2 other plasma cell disorders: monoclonal gammopathy of undetermined significance (MGUS) and smoldering myeloma (SMM). MGUS and SMM are therefore considered to be precancerous conditions with a risk for the development into MM of 1% and 10%, respectively.
Patient materials
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Symptoms
The most common causes for symptoms in MM patients are known by the acronym CRAB, in which C stands for calcium elevation, R for renal failure, A for anemia (i.e., a low level of red blood cells) and B for bone disease. However, the clinical symptoms vary from person to person. In the early stages of the disease, patients may not experience any symptoms at all and when symptoms develop, they are often vague, or mimic symptoms of other conditions.
Bone problems, including bone pain, bone weakness and fractures are a common symptom in patients with MM. In addition to this, low levels of normal blood cells can cause a broad range of symptoms. When patients have too few red blood cells (anemia) they often feel tired, dizzy, or weak and can suffer from shortness of breath. Due to a lack of normal immunoglobulins, MM patients also tend to easily pick up infections such as coughs or colds. Finally, a low number of platelets (thrombocytopenia) can lead to easy bruising and bleeding
Elevated levels of calcium in the blood (hypercalcemia) also cause a specific set of symptoms. This includes an extreme thirst, a frequent need to pee, dehydration, and kidney problems. In addition, high levels of calcium may also induce cognitive problems, such as confusion, or drowsiness.
Finally, excess levels of M protein in the blood can further decrease the kidney function of patients and can lead ‘hyperviscosity’ of the blood. The latter refers to a thickening of the blood due to high levels of protein and can lead to confusion, dizziness, and stroke-like symptoms.
Diagnostic tests
When MM is suspected, a blood test will be performed to measure the number of red blood cells, white blood cells and platelets in the blood. In addition to this, also the level of creatinine and calcium in the blood will be checked. Further blood tests (i.e., serum protein electrophoresis) allow the identification of the M-protein. A routine urine sample is usually also examined to look for M- protein that has filtered through the kidney.
The diagnostic work-up for MM also includes an evaluation of the bone marrow. To this end, a bone marrow sample is removed from the hipbone or sternum (breastbone) and sent to the lab for a further evaluation of the size, shape, and genetic features of the cells in the bone marrow.
To further assess the spread of the disease and evaluate which organs are affected by MM, medical imaging techniques, such as bone X-rays, MRI, and (PET)-CT are used.
Treatments
The treatment for MM can often help to control symptoms and improve the quality of life of patients. For the moment, MM is still incurable, which means that subsequent rounds of therapy are needed when the disease comes back.
The initial treatment for patients with MM can be intensive or non-intensive, depending on the age and fitness of the patient. While both approaches involve a combination of different anti-myeloma medicines, the intensive approach uses higher drug doses and is followed by a stem cell transplantation. In most patients, the MM will eventually return, requiring further treatment.
In the past, chemotherapy was one of the main treatment modalities for MM. More recently, however, chemotherapy has become less important due to the development of new anti-myeloma agents. Nowadays, treatment regimens for patients with MM consist of 2-3 different kinds of medicines. The types of drugs that are being used in these combinations are proteasome inhibitors (e.g., bortezomib, carfilzomib, ixazomib), immunomodulatory agents (e.g., lenalidomide, pomalidomide), monoclonal antibodies (e.g., daratumumab, isatuximab, elotuzumab) and corticosteroids (e.g., dexamethasone). The choice and dose of the different agents in these combinations depends on many factors, including the stage of the cancer, the fitness of the patient, the presence of certain comorbidities (e.g., heart condition, renal impairment, etc.) and previous therapies.
More recently, also bispecific antibodies and CAR-T cell therapy have entered the treatment arsenal for patients with MM. MM continues to be an active field of clinical research and as a result, participation in clinical trials may provide access to alternative treatment options.
Apart from treating the MM itself, patients may also receive therapy to alleviate symptoms, or counter complications. This may include the use of bisphosphonates to reduce the level of calcium in the blood, radiotherapy to the bone to relieve bone pain or enhance bone strength, plasma exchange to remove excessive amounts of M-protein from the blood, or a dialysis for patients with kidney failure.
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