Blood cancer

Blood cancers develop when blood cells fail to form correctly and start to grow uncontrollably in the bone marrow or lymphoid organs (ie; thymus, lymph node, spleen). Blood cancers do not produce solid tumours, but instead spread through the bloodstream or the lymphatic system. Due to a failure of normal blood cell development, blood cancers often result in anaemia (not enough red blood cells), bleeding (not enough platelets) and infections (not enough immune cells).

Some blood cancers are slow growing, while others form, grow and spread rapidly. Some blood cancers are more likely to affect children or older people.

Blood cancers are caused by changes to the DNA or genes responsible for blood cell production. We don’t know exactly what triggers these changes. Exposure to radiation or chemicals is linked with some but not all blood cancers.

There are three blood cancer groups.

1. Leukaemia occurs when abnormal blood cells in the bone marrow become cancerous.  Leukaemias can be acute (rapid onset and rapid progression) or chronic (slower onset and slower progression). They can affect either the myeloid cells (ie; red blood cells, platelets or non-lymphocyte white blood cells) or lymphoid cells (ie; T or B lymphocytes) in the bone marrow.

Chronic lymphocytic leukaemia (CLL) is the most common form of leukaemia diagnosed in Australia, mainly occurring in people aged over 60. CLL affects B lymphocytes and usually develops and progresses slowly, often not needing any treatment in the early stages.

Chronic myeloid leukaemia (CML) is less common than CLL and results in overproduction of immature and mature myeloid cells. Like CLL, CML is a slow growing leukaemia that can remain relatively stable for months or years. It can, however, progress into a more aggressive acute phase that more closely resembles an acute leukaemia.

Acute myeloid leukaemia (AML) results from accumulation of immature myeloid cells in the bone marrow, leading to a loss of normal blood cell production. AML affects about 1,000 Australians diagnosed each year and is more common in adults compared to children.

Acute lymphoid leukaemia (ALL) results from accumulation of immature lymphoid cells (B or T), and like AML results in loss of normal blood cell production. Around 400 Australians are diagnosed with ALL each year, with ALL being more common in children than adults.

2. Myeloproliferative neoplasms (MPNs) arise when the bone marrow makes too many of one or more types of mature blood cells (red blood cells, platelets or white blood cells). Symptoms develop due to accumulation of these mature cells in the blood, bone marrow and spleen.

3. Lymphoma develops in the lymphatic system from white blood cells, which help the body fight infections. The two main types are non-Hodgkin lymphoma (which accounts for about 90 per cent of lymphomas) and Hodgkin lymphoma, identified by the types of cells they contain. Lymphoma rates have been rising over the past 20 years, for reasons that aren’t yet clear.

Mantle cell lymphoma (MCL) is a rare but fast-growing form of non-Hodgkin lymphoma, affecting the B cells. Men are three times more likely than women to be diagnosed with MCL, usually after the age of 70.

4. Myeloma begins when abnormal plasma cells (a type of mature B lymphocyte) accumulate in the bone marrow and impair the production of normal blood cells. Myeloma accounts for 13 per cent of all blood cancers, with about 1,900 Australians, most aged over 60, diagnosed each year.

Some people are at higher risk of developing blood cancers from

• Exposure to intense radiation or previous treatment with chemotherapy or radiation therapy
• Exposure to certain industrial and agricultural chemicals or heavy metals, over a long period
• Some genetic disorders such as Down syndrome
• Infections such as the Human Immunodeficiency virus (HIV-AIDS) and the Epstein-Barr virus, and the Human T-Cell leukaemia virus.

Blood cancers are often first diagnosed following a visit to a GP for symptoms including tiredness, bruising, frequent infections and weight loss.  Diagnosis involves a physical examination and blood test, followed by confirmation of the blood cancer type using a biopsy, imaging (c-ray, CT or PET scans, ultrasound, MRI) and/or cytogenetic testing.

Treatments for blood cancers vary according to cancer type. They can include chemotherapy, steroid therapy, surgery, interferon, stem cell transplants, targeted drug therapies, immunotherapies, radiation therapy, and drugs only available through clinical trials.