Dr Aparna Dhar, HOD-Medical Genetics and Genetic Counselling, CORE Diagnostics talks about the role of molecular testing in blood cancer treatment
Blood cancers, also called hematologic malignancies, are the cancers of the blood, bone marrow, and lymph nodes. It is due to uncontrolled blood cell production and altered function. These cancers can affect anyone, including children. Hematological malignancies account for 8% of new cancer diagnoses in India.
However, misinformation and lack of awareness about blood cancer and its types are the biggest challenges observed today among the Indian population. Due to lack of awareness, people aren’t aware that blood cancer can be managed, a patient can have a second chance at life with chemotherapy, targeted therapy, stem cell transplant etc.
And, with the availability of advanced and sophisticated molecular diagnostic methods, we have answers to questions regarding cancer diagnosis, prognosis, risk stratification and the best course of treatment.
We’ll briefly discuss the types of blood cancers, the known or likely genes causing blood cancers, and a range of in vitro molecular diagnostics laboratory testing methods to detect them and help guide treatment options.
Blood cancer can be categorised as:
- Myeloid neoplasms (Acute myeloid leukemia, AML; Chronic myelogenous leukemia CML)
- Lymphoid neoplasms (Acute lymphoblastic leukemia, ALL; Chronic lymphocytic leukemia, CLL and Lymphomas)
- Myeloproliferative Neoplasms (polycythemia vera, essential thrombocythemia, primary myelofibrosis).
Of all types of blood cancers, the three most common types that affect the Indian population are Lymphoma (starts in the lymphatic system), Leukemia (starts in the bone marrow) and Multiple Myeloma (starts in the bone marrow).
Lymphomas and leukemia affect adults and children both, but Myeloma is a relatively common condition which affects adults. Acute Myeloid Leukemia (AML) is the most common type of leukemia in adults and Acute Lymphoblastic Leukemia (ALL) accounts for 25% of all childhood cancers. It is the most common malignancy in children.
What causes blood cancer?
The specific causes of blood cancer are not yet known. However, there are certain factors that contribute to blood cancer:
- Age: Different types of cancer affect people of different ranges, with Leukemia being the highest among children below 14 or above 40.
- Tobacco: consumption of tobacco is any form can lead to cancer. It can weaken the immune system and damage or alter a person’s DNA, making it susceptible to developing cancer cells which are difficult to control.
- Alcohol: excessive intake of alcohol can interfere with the production of new cells in your bone marrow.
- Exposure to radiation and harmful chemicals: With growing urbanisation and occupational changes in a growing country like India, exposure to harmful radiation and chemicals can lead to interference with your DNA, increasing your risk of developing blood cancer.
- Family history: If your family has had a history of haematological diseases, it is likely you will experience signs and symptoms of blood cancer as well.
Common symptoms to be on the lookout for are:
In most cases of blood cancer, the patient feels tired and weak. This is due to a decrease in the number of red blood cells in the blood which results in lack of blood.
Fever is a common symptom of cancer. The immunity becomes weak; thus, the patient often has a fever.
Prone to repeated infections. When leukemia cells develop in the body, then complaints of infection can be seen in the patient’s mouth, throat, skin, lungs, etc.
People who have cancer tend to have an abnormally low weight. If the body weight is reduced without any obvious cause, then it can be seen as the primary symptom of cancer.
Pain in bones and joints can be a symptom of not only arthritis but also blood cancer. As blood cancer is a disease in the bone marrow, large amounts can be seen around the bones and joints.
The abnormal formation of leukemia cells in the body prevents the bone marrow from producing healthy blood cells such as platelets. Due to its deficiency, more bleeding problems can be seen from the nose of the patient, during menstruation, gums, etc.
Testing
There are a plethora of tests offered to understand the molecular and genetic basis of blood cancers. These tests guide informed treatment- related decisions. A combination of various techniques, radiology (PET, CTscan etc.) and multiple biomarkers tested by different technologies can help shed light on a comprehensive understanding of the patient’s disease to the treating physician.
The diagnosis of AML is made using immunophenotyping and analysis of underlying genetic abnormalities using cytogenetics (for risk classification) and molecular testing. Analysis of FLT3, NPM1, and CEBPA genes are recommended as a minimum by international guidelines. Subtypes of AML, such as acute promyelocytic leukemia (APL), have specific molecular markers associated with them. Analysis of PML-RARA in APL is now standard of care.
CML is characterized by a specific chromosomal translocation (part of a chromosome fuses to part of another chromosome) of chromosomes 9 and 22 known as the Philadelphia chromosome. This characteristic chromosomal abnormality can be detected by cytogenetics, by FISH, or by PCR targeted at the BCR/ABL fusion gene. CML is treated using targeted drugs. These drugs are monitored using RT-PCR (molecular testing).
Diagnosis of CLL is made by examining smears of the peripheral blood and bone marrow, immunophenotyping and (IgVH) gene mutation status. Immunophenotyping of the patient’s cells plays a central role in the diagnosis of a patient with lymphoma. The immunophenotypic analysis will guide molecular test selection such as T-cell clonality analysis, IGVH analysis, or targeted FISH analysis.
Diagnosis of Multiple Myeloma is made by analysing the blood and urine sample for: M protein (electrophoresis), Quantitative immunoglobulins, Serum free light chains, serum albumin and serum beta-2 microglobulin (β2-M), Lactase dehydrogenase (LDH). In addition a bone marrow biopsy/aspirate is used to test for immunohistochemistry, flow cytometry, cytogenetics (FISH) or minimal residual disease test.
Treatment of blood cancer
Treatment depends on the type of blood cancer, age, how fast the cancer is progressing, and whether the cancer has spread to other parts of the body.
Because treatments for blood cancer have vastly improved over the last several decades, many types of blood cancers are now highly treatable. Common treatments include the following:
- Chemotherapy: Anticancer drugs are introduced to the body (via injection into the vein or sometimes by taking a pill) to kill and halt the production of cancer cells.
- Radiation therapy: This form of cancer treatment uses high-energy rays to kill cancer cells.
- Targeted therapies: This form of cancer treatment uses drugs that specifically kill malignant blood cells, without harming normal cells. Targeted therapies are most commonly used to treat leukemia.
- Stem cell transplantation: Healthy stem cells can be infused into your body to help resume healthy blood production following therapy to destroy malignant blood cells.
- Cancer surgery: This treatment involves removing the affected lymph nodes to treat some lymphomas.
- Immunotherapy: This treatment activates the immune system to specifically kill cancer cells.
Conclusion
There is a lack of awareness about blood cancer, especially among the rural population. Ignoring the symptoms at an early stage and/or delay in diagnosis leads to delay in seeking care. Every blood cancer patient who gets diagnosed early and has access to treatment is a victory in itself.
The challenge of the next decade now is to develop indigenous methods of delivering CAR-T cells, immunotherapies, and molecularly targeted therapies, and using them in the right combination and sequence in order to extend the quality and quantity of life meaningfully for
A minimum of 30% of the future cancer burden can be easily prevented, if necessary, measures are taken in the early stages. From tobacco sales and consumption control to expansion and equal distribution of medical facilities, awareness & education programs about risks, prevention, and bone marrow donation, a lot can be done to minimise the rise of blood cancer in India.
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