Ahead of Blood Cancer Awareness Month in September, this week’s #BIVDAblog is raising awareness of haematological malignancies and the role played by diagnostics.
The term ‘blood cancer’ is used to describe a broad range of malignancies (137 different types) affecting the blood, bone marrow, lymph, and lymphatic system. Almost 30,000 people are diagnosed with blood cancer every year in the UK, equating to over 70 people a day or one person every 20 minutes. These forms of cancer derive from either of the two major blood cell lineages – the myeloid and lymphoid cell lines – and are separated into three main groups: leukaemia, lymphoma and myeloma. Leukaemia, which results in high numbers of abnormal white blood cells, is diagnosed in 7,600 British people a year. Lymphoma, which describes malignancy that develops from lymphatic cells, is newly diagnosed in 11,700 people. Finally, myeloma, cancer of plasma cells, accounts for 3,750 diagnoses a year, whilst the final 5,350 cases are other, rare blood cancers.
Within these three main groups, however, there are many different types. There are four main types of leukaemia – acute myeloid leukaemia (AML), acute lymphoblastic leukaemia (ALL), chronic myeloid leukaemia (CML), and chronic lymphocytic leukaemia (CLL) – while lymphoma is often challenging to treat because there are so many different types (over 35 in total), which are split into the two main categories of Hodgkin lymphoma and non-Hodgkin lymphoma. Non-Hodgkin lymphomas are a diverse group of cancers, ranging from slow growing to extremely aggressive, that represent the sixth most common cancer in the UK, whilst leukaemia is the eleventh most common and most common in children.
There are many specific genetic variations that cause specific types of blood cancer. Uncommon in solid tumours, chromosomal translocations are a common cause of haematological malignancy. Depending on the point at which a chromosome breaks, a translocation can result in the disruption or misregulation of normal function, or alternatively the production of oncogenes (genes with the potential to cause cancer) through the fusion of the coding region of two genes.
In patients with Burkitt’s lymphoma, for example, a common translocation places the myc gene, which codes for a protein involved in cellular proliferation, under the control of a powerful immunoglobulin promoter, meaning the MYC protein is highly overexpressed in lymphoid cells. Meanwhile, the ‘Philadelphia translocation’, most commonly associated with CML (found in 95% of CML patients), creates the bcr-abl fusion gene, a powerful oncogene.
As a result of the genetic differences between blood cancers and other cancers, a different approach to diagnosis and treatment is often adopted. As with many other cancers, however, diagnosis is still largely dependent on in vitro diagnostics. Indeed, a variety of different IVD techniques can be used in combination to reveal the presence of blood cancer, before identifying the specific malignancy.
Initially, a full blood count can show whether there are too many or too few of a type of blood cell, or identify the presence of an abnormal cell in the blood. A blood film is also useful as malignant cells can show in characteristic ways on light microscopy. Further information can be obtained through the use of flow cytometry, which detects cell surface antigens present on the different blood cell lineages and can identify abnormal cells. For example, while CLL cells have many of the same markers as normal B-cells, they also possess an antigen called CD5 that is normally found on T-cells not B-cells – a clear indication that the B-cells are abnormal. Furthermore, some studies suggest that patients with fewer cells with a non-normal antigen profile have a better prognosis, meaning flow cytometry can help to stage the cancer, which has to be done differently to most other types of cancer due to the lack of measureable solid masses.
A bone marrow biopsy, which allows the number and appearance of certain cells within the bone marrow to be studied under a microscope, is often used to confirm the diagnosis. Additionally, a lymph node biopsy will often be used to diagnose lymphoma, particularly if they are enlarged, whilst a lumbar puncture may be performed to look for leukaemic cells in the cerebrospinal fluid if leukaemia is found in the bone marrow.
Finally, genetic testing can play a significant role in the diagnosis of blood cancers, identifying the genetic makeup of cancerous cells and allowing the most appropriate treatment to be selected as a result. Techniques known as karyotyping and fluorescent in-situ hybridization (FISH) are used to look for numerical and structural chromosomal abnormalities (such as deletions and translocations), whilst mutation analysis can locate smaller changes in the DNA through the use of techniques such as the polymerase chain reaction. These methods enable the exact nature an individual’s disease to be identified, aiding the prognosis of the patient and the development of a therapeutic approach tailored to the individual in question. Once again, a fantastic example of the crucial role played by in vitro diagnostic techniques in personalised medicine, improving treatment for patients whilst saving money by avoiding the use of treatment options that are always likely to be ineffective for certain patients.
Statistics on incidence, survival and prevalence of blood cancers courtesy of the Haematological Malignancy Research Network (HMRN).
Blood cancer charities
- Anthony Nolan
- Delete Blood Cancer
- Leukaemia and Lymphoma Research
- Leukaemia Care
- Lymphoma Association
(Thumbnail Photo: http://www.rsc.org/Publishing/Journals/cb/Volume/2009/9/blood_cells_get_active.asp)