What are blood cancers?

Risk factors: The risk factors and causes of many types of blood cancers are not well known, and most cases of blood cancer occur in individuals with no identifiable risk factors. However, for AML, which along with CLL is among the most common types of blood cancer seen in adults, these specific risk factors have been found: Down syndrome and other genetic disorders, chronic exposure to ionizing radiation and chemicals such as benzene in the workplace, high doses of radiation therapy and chemotherapy to treat lymphoma or other types of cancer, and tobacco smoke. Those who are immunocompromised by certain bacteria or human retroviruses, such as the Epstein-Barr virus (EBV), human immunodeficiency virus (HIV), or human T-cell leukemia virus (HTLV), are at greater risk of developing lymphomas. Familial clustering also has been associated with the development of lymphomas.

Etiology and the disease process: Cancer develops as a result of a variety of factors and over a number of years. Blood cancers differ widely by group and within each subtype in their progression, causes, and molecular presentation. The leukemias begin in two types of white blood cells: neutrophils and monocytes, which are germ-ingesting cells, and lymphocytes, which are immune-defense cells. Abnormal white blood cells in the bone marrow multiply and enter the bloodstream, crowding out normal cells. Lymphomas develop when these immune-defense cells multiply and cause tumors in the lymph nodes or other parts of the immune system. Development of blood cells through the hematopoietic process is arrested, and abnormal blood cells proliferate. Every stage of hematopoietic development can result in a particular type of cancer. Non-Hodgkin lymphoma (NHL) is manifested by well-differentiated cells with slow progression, while other forms are more aggressive with lymphocytes of limited differentiation. Tumors of the bone marrow are characteristic of myelomas. In myeloma, cells that are to become immune cells develop in the bone marrow from stem cells, as do all blood cells. B lymphocytes, which are a type of white blood cell that typically develop into plasma cells, undergo multiple genetic changes as they change into plasma cells, causing malignant plasma cells to develop. These myeloma cells travel throughout the bloodstream, reside in the bone marrow, and damage healthy tissue. The myeloma interferes with the plasma cell’s production of protective proteins called immunoglobulins or antibodies by producing M proteins or abnormal immunoglobulin, making those affected susceptible to infection.

Incidence: As reported by the Leukemia & Lymphoma Society (LLS) in April 2014, the most common forms of leukemia seen in adults are chronic lymphocytic leukemia (CLL) and acute myelogenous leukemia (AML). The most common form in children and young adults is acute lymphocytic leukemia (ALL), accounting for 74 percent of new leukemia cases in the under-twenty population in 2010. The average median age at diagnosis for leukemia was sixty-six, with incidences of CLL and AML beginning to increase significantly at age fifty and older and incidences of chronic myelogenous leukemia (CML) increasing significantly above age sixty-five. Between 2006 and 2010, the age-adjusted incidence rate for leukemia was 12.8 per 100,000 men and women per year. In the United States in 2014, new cases of ALL were estimated to number 6,020; new cases of AML, 18,860; CLL, 15,720; and CML, 5,980. Overall, chronic leukemias accounted for an estimated 6 percent more cases than acute leukemias. Incidence rates for all types of leukemia are higher among men than women and higher among those of African descent than those of European descent.

The LLS reported that an estimated 79,990 cases of lymphoma would be diagnosed in the United States in 2014. The majority of these cases (70,800) were projected to be of the non-Hodgkin type. Incidence rates of both Hodgkin and non-Hodgkin lymphoma tend to be higher for men than women; between 2006 and 2010, the incidence among men was 3.2 per 100,000 for Hodgkin lymphoma and 23.9 per 100,000 for non-Hodgkin lymphoma, while incidence rates among women were 2.4 per 100,000 and 16.4 per 100,000, respectively. New cases of Hodgkin lymphoma peak in young adults between ages twenty and twenty-four, decrease throughout middle age, then begin to increase again after age sixty, while incidence rates of non-Hodgkin lymphoma remain low until age fifty and above. Non-Hodgkin lymphoma is the sixth most common cause of cancer deaths among men and the seventh most common among women.

It was estimated that 24,050 new cases of myeloma would be diagnosed in the United States in 2014. The LLS reported that between 2006 and 2010, the median age for diagnosis of myeloma was sixty-nine, with the highest incidence rates—39.7 per 100,000—occurring between ages eighty and eighty-four. The incidence rate of myeloma is higher for men than women across racial and ethnic groups: 7.5 per 100,000 among men, compared to 4.8 per 100,000 among women.

Symptoms: Signs and symptoms of blood cancers vary widely and may be similar to those of other, less severe illnesses. Symptoms vary based on the category and subtype of blood cancer; for example, symptoms of acute leukemia may include pallor, shortness of breath with exertion, lack of energy, night sweats or a mild fever, slow healing of cuts and bruises, unexplained weight loss, tiny red spots under the skin, bone and joint aches and pains, and low white blood cell count (especially neutrophils and monocytes). Although specific bone marrow and blood tests are needed to diagnose any type of blood cancer, some of those affected with certain subtypes of leukemia may have enlarged lymph nodes in the neck, groin, or armpit, and they may suffer from frequent infections.

Often individuals who have Hodgkin disease or non-Hodgkin lymphoma experience painless, swollen lymph nodes, loss of appetite, vomiting, bloating, abdominal pain, fullness (due to enlargement of the liver, spleen, or abdominal lymph nodes), pain in the lower back, bone pain, constant coughing, and unexplained lethargy.

Early symptoms of myeloma are bone pain, particularly with movement, and infections involving the skin, the urinary tract, the bronchial tract, or lungs. These symptoms may also be accompanied by pallor resulting from anemia, weakness, and exaggerated fatigue.

Screening and diagnosis: Blood tests and specific bone marrow tests are needed to diagnose blood cancer; however, individuals in early stages of the disease may not have symptoms suggesting cancer. Current evidence does not suggest that routine blood screening before the onset of symptoms will detect cases of blood cancer and lead to improved medical outcomes or be cost effective in those at average risk of developing cancer according to their medical, family, and occupational history. The first indication that a person has blood cancer may be the results of a blood test performed as part of an annual physical. The blood sample may reveal anemia or changes in white blood cells, a possible indicator of leukemia. If an individual has symptoms that suggest blood cancer, the physician will take a medical history and check for swelling of the liver, spleen, or lymph nodes in the armpits, groin, or neck. Urinalysis will also be performed to detect substances or cellular material in the urine. Other tests include a blood test to assess blood cell count, a cytogenetic exam to analyze the number and shape of chromosomes to check for genetic abnormalities, and bone marrow aspiration and biopsy to check for cancerous cells in liquid bone marrow or the bone specimen. If cancerous cells are present, additional tests may be ordered to ascertain if the disease has spread and to organs or systems. These tests may include tumor marker tests (immunophenotyping, based on the type of antigen or marker on the surface of the cell), a spinal tap or lumbar puncture to obtain a sample of cerebrospinal fluid, chest x-rays to look for signs of infection or lymph-node involvement, or ultrasound scans.

Staging is used to assess the extent or severity of the disease, to plan treatment, and to predict the outcome or prognosis. Classification of each type of blood cancer into stages is based on the site that is affected, the progression of the disease, and the appearance of the affected cells. For example, CLL is staged according to the risk-based Rai classification system, using symptoms such as blood lymphocyte count, presence of enlarged lymph nodes or organs, platelet count, and anemia. Other forms of leukemia, such as acute leukemia, are not staged because of acute onset, which typically means the cancer has spread to other organs at the time of diagnosis.

Although leukemic cancerous cells circulate in the blood and bone marrow, in lymphomas cells form tumors in lymphatic tissue. The Ann Arbor staging system is used for both Hodgkin disease and non-Hodgkin lymphomas on the basis of specificity of site of lymph-node involvement. The TNM (tumor/lymph node/metastasis) system may be used to stage the size of a tumor, lymph-node involvement, and existence or extent of spread through other parts of the body. The International Staging System (ISS) is used for staging multiple myelomas based on blood tests for two proteins, albumin and beta-microglobulin, which are markers for the disease.

Treatment and therapy: Blood cancers are typically treated with one or more of the following: chemotherapy, radiation therapy, stem-cell transplantation, and immunotherapy. The goal of chemotherapy, drugs given in combination and via different methods of delivery, is to destroy cancerous cells or to stop them from growing and multiplying, producing long-term remission or a cure. Radiation therapy may be used to treat localized cancers such as lymphomas and certain types of leukemia, or it may be used to relieve symptoms when cancerous growths cause pain or pressure on bones, nerves, or organs. However, chemotherapy and radiation therapy can cause long-term or late effects, affecting fertility or growth and causing learning disabilities or illnesses secondary to the primary cancer, such as leukemia.

Chemotherapy doses considered tolerable by most patients may not be sufficient to arrest, cause remission in, or cure acute leukemia, myeloma, or lymphoma. In patients who may be at high risk of relapse, who relapse after a successful course of treatment, or who do not respond as expected to conventional treatment, stem cell transplantation can enable production of normal blood cells such that intensive chemotherapy can bring about recovery. Immunotherapy, using antibodies from the patient or a donor, may be used alone or in combination with other therapies to attack cells that remain after chemotherapy and that may attach to antigens on the malignant cells. They also are used as vaccines to suppress malignant cells that remain in the body following therapy.

New chemotherapies, immunotherapies, vaccines, gene therapies, and types of bone marrow transplants to suppress the growth of cancerous cells and affect the course of the disease are always being developed and tested. Patients should be reminded that pain and uncomfortable symptoms arising from the toxic effects of cancer treatments can be managed by consulting with their physicians. Supportive care to improve functioning and quality of life, transfusions, antibiotics to protect against infection, and a healthy diet and lifestyle are critical for those undergoing cancer treatment.

Prognosis, prevention, and outcomes: Many factors affect the outcome of a patient’s blood cancer, including the type, location, and stage of disease, as well as individual and demographic factors such as the person’s general health, age, and response to treatment. A cancer survivor will undergo follow-up care, which includes frequent monitoring of blood counts, x-rays, urine tests, and imaging tests such as computed tomography (CT) or positron emission tomography (PET) scans. Those whose remission lasts five years are considered cured. Five-year survival rates for those with blood cancer have been rising since 1975 and the advent of more effective cancer treatments.

No specific guidelines for preventing blood cancer exist, as its causes are not known and many types are relatively rare. Limiting exposure to environmental toxins and leading a healthy lifestyle may help prevent blood cancers in those of average risk. The relative overall five-year survival rate of leukemia for those diagnosed between 2003 and 2009 was 59 percent—nearly double the rate for those diagnosed between 1975 and 1977 (34 percent), according to the LLS. Relative survival rates vary by age at diagnosis, race, gender, and type of leukemia. Of all types of leukemia, those with CLL had the highest relative survival rate during this period, at 83.1 percent.

Hodgkin disease is considered one of the most curable cancers, with many patients cured after their initial treatment. The five-year survival rate has increased substantially since the 1970s, from 72 percent to 88 percent. Similarly, due to advances in treatment of non-Hodgkin lymphoma, the five-year survival rate has increased from 47 percent in the 1970s to 71 percent in those diagnosed between 2003 and 2009.

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