Myelodysplastic sydrome (MDS) is a disorder in which the bone marrow stops being able to produce enough blood cells. It is caused by acquired (that is, not inherited) genetic damage to the marrow stem cells and mainly affects those over age sixty. The reason for the stem cell damage is usually unknown, although some cases are caused by exposure to benzene, radiation, or certain types of chemotherapy. Analysis of the name myelodysplasia is the first step toward understanding this confusing disorder: myelo is Greek for marrow, dys- means abnormal, and -plasia means formation or development. Thus, myelodys- plasia means abnormal bone marrow development. The result is insufficient blood formation for the needs of the body.
MDS is usually diagnosed when weakness, infection, or bleeding causes a person to seek medical help; some cases are found on routine blood testing before symptoms arise. Analysis of the CBC will show reductions in one, two, or three of the blood counts (red, white, platelets). The patient will then be referred to a hematologist, who will rule out other causes of low blood counts (such as deficiencies of vitamin B12, folic acid, and iron) and perform a bone marrow biopsy.
A curious finding in MDS is that, although the disorder is characterized by lower than normal blood counts, a patient’s bone marrow will often exhibit an excess of blood-producing cells compared to normal. The appearance of the MDS marrow cells, however, is bizarre; they are misshapen, abnormally enlarged, and altered in a way that enables them to be labeled dysplastic. The problem is that the exuberant growth is exceeded by accelerated cell death: instead of releasing healthy blood cells into the circulation, MDS cells mostly die in the bone marrow. Although MDS is not a cancer, the dysplastic and damaged marrow stem cells are primed to sustain further damage and be converted into leukemia. The likelihood of conversion to leukemia can be predicted with some accuracy and is highly correlated with overall survival (the greater the chance of leukemia, the lower the survival). The method of prediction is called the International Prognostic Scoring System (IPSS). The IPSS uses three criteria to determine if a patient has a low, intermediate, or high risk of developing leukemia. They are:
1. The percentage of bone marrow cells that are leukemia blasts (ranging from less than 5 percent to 20 percent).
2. The chromosome pattern of the bone marrow cells.
3. The number of blood counts (one, two, or three) that are low, considering the red cells, white cells, and platelets.
An MDS patient’s hematologist will calculate the IPSS score and risk category, which will dictate the possible treatments. Those with low or low to intermediate scores may need only a low-intensity approach to maintain their blood counts, such as blood transfusions or injections of blood cell growth factors. Those with intermediate to high IPSS scores may require chemotherapy followed by a stem cell transplant from another person in an effort to eradicate the diseased marrow. Patients with any score may benefit from the drug azacytidine (Vidaza), which is a form of low-intensity chemotherapy. When Vidaza works well, it can diminish the need for blood transfusions, delay the onset of leukemia, and extend life. The related drug decitabine (Dacogen) was recently approved by the FDA for use in MDS patients with high or intermediate IPSS categories. Some patients may benefit from infusions of antithymocyte globulin (ATG), a horse or rabbit serum that suppresses the immune system (which may be attacking the bone marrow). A special category of MDS is that characterized by a 5q minus chromosome abnormality (also called deletion 5q). Patients with such an abnormality in their bone marrow may respond well to the drug lenalidomide (Revlimid), which can induce dramatic improvements in red blood counts and liberate them from blood transfusions.
In 1832 a distinguished English physician named Thomas Hodgkin reported on a group of patients who had a rapidly fatal disease characterized by greatly enlarged lymph nodes and swelling of the liver and spleen. He did not know what caused the disease and did not mention cancer in his seminal publication. He treated one patient with cascarilla and soda without effect and recommended caustic potash for less advanced cases. Please don’t ask me what these treatments were! Let’s just be relieved and grateful to the physicians and scientists who have contributed to today’s understanding that Hodgkin’s disease is a type of lymphoma (now called Hodgkin lymphoma) and that modern treatments can cure more than 75 percent of cases.
Lymphomas are the most common hematologic malignancy. There are two main categories, Hodgkin lymphoma (HL) and non-Hodgkin’s lymphoma (NHL). NHL occurs much more often than HL. The type is determined by a pathologist’s analysis of a biopsy specimen. Lymphomas can arise virtually anywhere in the body because of the widespread distribution of lymph cells and lymph nodes. Although lymphomas may cause any of a number of symptoms, most cases are detected after a patient feels a swollen lymph node or the enlarged node presses on a vital organ, causing internal symptoms.
If the diagnosis is non-Hodgkin’s lymphoma, testing will reveal if it derives from B- or T-cells (80 percent are from B-cells). Hodgkin lymphoma is always of B-cell origin. Current classification systems recognize five types of HL and more than thirty types of NHL. Whereas HL mainly affects young adults and those fifty-five or older, NHL typically affects those over age fifty (some forms are more common in younger individuals). I have many excellent resources to learn about both HL and NHL. I focus on non-Hodgkin’s lymphoma.
Decades of sophisticated scientific research into the mysteries of the immune system have enabled us to understand the origins of the many kinds of non-Hodgkin’s lymphoma. Normal lymphocytes go through a multistep process of maturation from bone marrow stem cell to fully functional infection-fighting immune cell. Each step is represented by a specific cell type, and each of these cells can be affected by the malignant process and give rise to a lymphoma. This is why there are so many types of NHL.
The oncologist will tell a patient the specific type of NHL he or she has. Follicular lymphoma and diffuse large cell lymphoma are the two most common types; less common types include small lymphocytic, mantle cell, lymphoplasmacytic (Waldenstrom’s macroglobulinema), MALT (mucosa-associated lymphatic tissue), and peripheral T-cell lymphomas. The doctor will also state whether it falls into the low-, intermediate-, or high-grade category. The grade relates to how aggressively the lymphoma is likely to grow: low-grade types grow over years, whereas intermediate-grade lymphomas grow over months, and high-grade lymphomas grow even faster. To relate this to the concepts of growth and apoptosis, low-grade lymphomas are marked by diminished apoptosis, whereas intermediate- and highgrade lymphomas have accelerated growth as their defining characteristic. If lymphoma can be thought of as a pot of boiling water, then lowgrade lymphomas are at a gentle simmer, whereas high-grade ones are on a rapid boil.
The faster growing the lymphoma, the more urgent the need for treatment. It is also often the case that the faster growing the lymphoma, the greater the chances that it can be eradicated with chemotherapy. This is why patients with diffuse large cell lymphoma, for example, are told that there is a good chance for cure with treatment, whereas those with low-grade lymphomas are told that we do not yet know how to eradicate this disease.
As illustrated by the case of Don, the seventy-five-year-old with lymphoma, some low-grade lymphomas are observed closely and not treated until necessary; approximately 20 percent will actually undergo spontaneous remission and shrink for a time without treatment. If fever, night sweats, weakness, or progressive enlargement of lymph nodes occurs, then treatment might be necessary. When the time comes, a number of highly effective treatments are available to control the disease.
Just as I have emphasized in other cancers, no two lymphomas are exactly alike. Focusing on the most common type of NHL, B-cell diffuse large cell lymphoma, about half of all cases will be cured with a treatment regimen called CHOP-Rituxan. This consists of three chemotherapy drugs administered intravenously (C = Cytoxan or cyclophosphamide, H = hydroxy-daunorubicin or doxorubicin/Adriamycin, and O = Oncovin or vincristine); an oral steroid medicine, called prednisone (P); and a genetically engineered antibody that specifically attacks B-cell lymphomas, called rituximab (Rituxan), which is administered intravenously along with chemotherapy.
Can it be predicted who will and who won’t be cured with CHOPRituxan? Oncologists employ a prognostic system called the IPI (International Prognostic Index) to each case of diffuse large cell lymphoma to classify it into a low-, intermediate-, or high-risk category; the higher the risk, the lower the chances for cure. A related system called the FLIPI (Follicular Lymphoma IPI) can be applied to cases of follicular lymphoma. Both the IPI and the FLIPI use clinical information, such as the patient’s age, the stage of the cancer, and the elevation (or lack thereof ) of the blood marker LDH (lactate dehydrogenase). But it is not a perfect way to predict survival. A more sophisticated method based on determining the genetic makeup of the lymphoma is being pioneered and is hoped to be available in the near future. Patients with NHL often confront a complex disease that has many good treatment options. New and effective therapies for lymphoma are rapidly being developed. Cure or long-term disease control should always be the goal. This may be achieved with chemotherapy drugs, antibody therapies, radioactive antibodies, or a stem cell transplant. Although innovative approaches such as lymphoma-specific vaccines were not successful in recently performed clinical trials, harnessing a patient’s own immune system to control his or her lymphoma will continue to be a major focus of researchers.
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