Ask the Doc: Could I get blood cancer from exposure to harmful pesticides?

In the final instalment of a four-part Q&A series on cancer, Dr Dawn Mya Hae Tha, a senior consultant of haematology at Parkway Cancer Centre, discusses blood cancers and the new treatment, CAR T-cell therapy

The most prevalent blood cancer is lymphoma, which carries symptoms such as night sweats, fatigue, a sickly pallor or joint pain. PHOTO: GETTY IMAGES

Which is the most prevalent blood cancer in Singapore, and what are common signs and symptoms to look out for?

The most prevalent blood cancer is lymphoma. Blood cancers usually originate in the bone marrow, lymph nodes, or various organs. They can also spread to other organs. Symptoms are related to the specific organ affected; for example, there could be abdominal swelling and pain if the liver and spleen are enlarged.

Common symptoms include fever, weight loss, night sweats, bleeding, fatigue, a sickly pallor, lymph node swelling, bone and joint pain.

How do blood cancers differ from one another?

Blood cancers can be divided into three categories:

Acute or Aggressive
From the onset, acute leukaemia and aggressive or high-grade lymphoma progress rapidly in a matter of a few weeks to a few months. Without treatment, death is almost always imminent.

Chronic leukaemia, indolent/ low-grade lymphoma and multiple myeloma can go undetected over a long period of time - from many months to years - until the patient becomes symptomatic. Some conditions can be monitored without being treated, till symptoms and indications surface.

Myelodysplastic syndrome and myeloproliferative diseases are blood disorders that can vary from mild to severe conditions. Mild disorders can remain dormant for years, yet progress to severe conditions or transform into acute leukaemia.

What are some of the risk factors for blood cancers?

While the exact cause of blood cancers is generally unknown, associated risk factors have been identified for specific diseases.

Acute myeloid leukaemia is known to be associated with previous exposure to agents toxic to cells (like chemotherapy and radiotherapy for previous cancers); harmful chemicals and pesticides; and underlying chronic blood disorders such as myelodysplastic syndrome and myeloproliferative neoplasms.

Some blood cancers are also linked to inherited and acquired genetic mutations, or chronic viral conditions such as the Human Immunodeficiency Virus or Epstein Barr Virus.

Ethnic variation can also be found in the prevalence of some blood cancers. For example, chronic lymphocytic leukaemia is more prevalent in Caucasians but T-cell lymphoma is more prevalent in Asians.

Apart from blood tests, blood grouping may also be necessary at the diagnosis stage because patients frequently need a blood transfusion. PHOTO: GETTY IMAGES

How are leukaemia, lymphoma, myeloma diagnosed?

Mainly by detecting cancer cells in involved tissues or organs.

Bone marrow tests can be carried out to detect cancer cells originating from there. The tests will also detect the spread of cancer cells from other parts of the body to the bones. For instance, lymphoma usually originates in the lymphoid tissue and can spread to other parts of the body, including bones.

Blood tests can detect cancer cells present in a patient's blood. Basic screening tests including kidney and liver function are done, prior to treatment. Infectious disease screening can be done to uncover associated infections, and blood grouping may also be necessary at the diagnosis stage because patients frequently need a blood transfusion.

Imaging studies, computerised tomography (CT) scan, positron emission tomography (PET-CT scan) and magnetic resonance imaging (MRI) scans can also evaluate the stage of blood cancers (usually in lymphoma).

A lumbar puncture and or cerebrospinal fluid examination may also be performed to evaluate if blood cancer has spread to the brain and the spinal cord.

What are treatment options available?

Aimed at achieving durable remission, leading to the cure of the disease, treatment options vary depending on the type of blood cancers.

A combination of chemotherapy, chemoimmunotherapy and/or targeted drugs are used to induce remission in blood cancers. Subsequently, further rounds of the same treatments, or consolidation with peripheral blood or bone marrow stem cell transplantation will be done. Sometimes, radiotherapy is used as a consolidation therapy. Some patients may also need maintenance therapy.

Should there be a relapse, salvage therapy can be done with available conventional treatment options, or via clinical trials. Newer treatment options for relapsed diseases include immunotherapy like Bispecific T-cell Engagers and cell therapy like Chimeric Antigen Receptor T-cells.

What is CAR T-cell therapy, and how promising is it?

Cancer cells survive by suppressing or bypassing the immune system. T-cells are a type of immune cells that keep abnormal cells in check, and kill cancer cells. While a patient's T-cells cannot recognise or kill cancer cells on their own, they can be modified into chimeric antigen receptor (CAR) T-cells.

It involves altering the genes inside T cells to help them attack cancer cells, and has been approved by the U.S. Food and Drug Administration for use among a specific group of patients.

Anti-CD19 CAR-T treatment can be delivered for relapsed acute lymphoblastic leukaemia in children and adults aged below 25 (recently approved in Singapore), Anti-CD19 CAR-T treatment is also available for relapsed diffuse large B-cell lymphoma, and anti-BCMA CAR-T treatment addresses relapsed multiple myeloma.

Potential side effects such as neurological complications and cytokine release syndrome as a result of overwhelming immune activation can be expected, so a multidisciplinary team approach among experts is necessary to help manage patients undergoing this type of treatment.

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