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An overview of blood cancers

Hematological cancers, also known as blood cancers or hematologic malignancies, are a group of cancers that affect the bone marrow, blood cells and/or lymphatic system. These cancers affect the production and function of blood cells, leading to a range of symptoms and complications, and are the fourth most common cause of cancer mortality in the population. In this article, we will explore the different types of hematological cancers, the available diagnostic methods, treatment options, ongoing research in the field and recent advances.


Types of Hematological Cancers

Hematological cancers can be classified into three main types of blood and bone marrow cancers: leukemia, lymphoma, and myeloma (Jiang et al., 2022). While lymphoma tends to affect the lymph nodes and related tissues, leukemia affects the blood and bone marrow. In the case of myeloma, plasma cells, which are in charge of creating antibodies, are the affected ones, weakening the immune system (Figure 1).

Figure 1. Type of blood cancers (PW, 2023).

Leukemias are originated in the blood and the bone marrow. This type of cancer occurs when the body creates too many abnormal white blood cells, interfering with the bone marrow’s ability to make other blood cells, such as red blood cells and platelets. Since the bone marrow is occupied by these abnormal white blood cells, there is less space for the production of red blood cells and platelets, leading to different problems like anemia. Leukemia can also be divided into four different types. Acute lymphoblastic leukemia (ALL) and acute myeloid leukemia (AML), which primarily affect children and adults, respectively, are two types that progress rapidly. In contrast, chronic lymphocytic leukemia (CLL) and chronic myeloid leukemia (CML) are slower-growing types that commonly affect older adults (Juliusson & Hough, 2016).


Lymphomas are cancers that originate in the lymphatic system, a network of vessels, nodes and organs that filter waste and toxins and help fight infection. Lymphomas can also be divided into two main types: Hodgkin lymphoma (HL) and non-Hodgkin lymphoma (NHL). The main difference between non-Hodgkin and Hodgkin lymphoma is that the Hodgkin one is characterized by the presence of abnormal lymphocytes called Reed-Sternberg cells that can be detected in the diagnosis to differentiate between these two types of lymphomas, as Hodgkin lymphoma tends to progress in a more predictable way than non-Hodgkin lymphoma, making it easier to recognize and treat (Mugnaini & Ghosh, 2016).


Multiple myeloma, also known as myeloma, is a cancer of plasma cells, which are a type of white blood cell responsible for producing antibodies. Myeloma cells accumulate in the bone marrow, leading to the production of abnormal antibodies and interference with the capacity of the organism to produce normal blood cells (Firth, 2019).

Symptoms and Diagnosis

The symptoms of blood cancers are diverse and can vary depending on the specific type and stage of cancer. However, some common symptoms are persistent fatigue, unexplained weight loss, frequent infections, enlarged lymph nodes, easy bruising or bleeding, bone pain, shortness of breath and night sweats (Figure 2) (Garg et al., 2021).

Figure 2. Symptoms of blood cancers (Blood cancer UK, 2023).

To diagnose blood cancers, apart from suspecting based on different symptoms, doctors also use different methods to confirm the diagnosis of a blood cancer and the subtype of it. A thorough physical examination is conducted to check for any enlarged lymph nodes, organ enlargement, or other signs of cancer. Blood tests, such as complete blood count (CBC), can help identify abnormalities in the number and type of blood cells. Imaging tests like X-rays, CT scans, MRI scans, or PET scans may also be used to determine the extent of the disease and identify any abnormalities in the lymph nodes organs (small organs that are part of the lymphatic system principally located in the neck, armpits, groin, abdomen, and chest), or bones. If there is a suspicion of blood cancer, a bone marrow aspiration and/or biopsy can be performed. In this procedure, a small sample of bone marrow is taken from the hipbone or sternum using a needle. Then, the sample is examined under a microscope to detect if there are cancer cells and can also be used to identify the probable subtype of the blood cancer.


Treatment Options

There a different treatment options for blood cancers (Figure 3); choosing one or another will depend on several factors, including the type of cancer, its stage, the patient's age and overall health. Traditionally, the most used treatments have been chemotherapy and/or radiotherapy (Kansara & Speziali, 2020). Chemotherapy uses different drugs to kill cancer cells or slow down their growth, it can be administered orally, intravenously, or directly into the spinal fluid. Radiation therapy follows the same principle as chemotherapy to kill cancer cells. The difference is that it involves the use of high-energy radiation to destroy them; it is more commonly used in localized lymphomas or as a part of the conditioning regimen before a stem cell transplant. The problem with these two therapies is that they destroy both cancerous and healthy cells, as they are not directed therapies that can distinguish between malignant and normal ones.

Figure 3. Current available treatment strategies for blood cancer (Garg 2021).

Nowadays, there are other novel therapies that are more specific to treat cancers that are known as immunotherapies. Immunotherapy enhances the body's immune system to recognize and attack specific cancer cells, avoiding the destruction of healthy cells and their source effects. Monoclonal antibodies and CAR-T cell therapy are examples of immunotherapies used in hematological cancers. Monoclonal antibodies recognize specific molecules (antigens) that are expressed on the surface of cancer cells. When recognizing them, immune cells can be activated to eliminate them or they can also block some mechanisms that cancer cells use to survive (Tsao et al., 2021). CAR-T cells are a revolutionary immunotherapy that uses engineered synthetic immune cells that recognize and eliminate cells that express a specific target antigen without affecting healthy cells (Sterner & Sterner, 2021).


Normally blood cancers are treated using a combination of traditional chemotherapy and radiotherapy with immunotherapies. Moreover, apart from those treatments, in some cases, there is also a need to perform a bone marrow transplantation (Simpson & Dazzi, 2019). The bone marrow transplantation involves replacing diseased or damaged bone marrow with healthy stem cells to restore normal blood cell production. It is often used for high-risk subtypes of cancer or for patients who here already cured with the therapies already mentioned but relapsed and got the disease again in a short time.


Advancements in the understanding of hematological cancers and the development of targeted therapies have significantly improved patient outcomes. Researchers are continuously studying the underlying molecular and genetic mechanisms of these cancers, leading to the identification of potential therapeutic targets. Clinical trials are ongoing to test novel treatment approaches, including targeted therapies, immunotherapies, and gene therapies.


Conclusion

Hematological cancers encompass a range of malignancies that affect the blood, bone marrow and lymphatic system. Understanding the different types, causes, symptoms, and diagnostic methods is crucial for early detection and appropriate management. While treatment options have improved over the years, ongoing research and clinical trials offer hope for more effective therapies and improved outcomes for patients with hematological cancers. Awareness, early detection, and access to appropriate medical care remain key in the fight against these challenging diseases.




Bibliographical References

Firth, J. (2019). Haematology: Multiple Myeloma. Clin. Med. 19, 58–60. https://www.rcpjournals.org/content/clinmedicine/19/1/58 Garg, A., Garg, S., Mishra, N., Enaganti, S., and Shukla, A. (2021). Chapter 12 - Advanced Drug Delivery Systems in Blood Cancer. In Advanced Drug Delivery Systems in the Management of Cancer, K. Dua, M. Mehta, T. de Jesus Andreoli Pinto, L.G. Pont, K.A. Williams, and M.J. Rathbone, eds. (Academic Press), pp. 141–154. https://www.sciencedirect.com/science/article/abs/pii/B9780323855037000080?via%3Dihub Jiang, Y., Lin, W., and Zhu, L. (2022). Targeted Drug Delivery for the Treatment of Blood Cancers. Molecules 27. https://www.mdpi.com/1420-3049/27/4/1310 Juliusson, G., and Hough, R. (2016). Leukemia. Prog. Tumor Res. 43, 87–100. https://karger.com/books/book/142/chapter-abstract/5079491/Leukemia?redirectedFrom=fulltext Kansara, R.R., and Speziali, C. (2020). Immunotherapy in Hematologic Malignancies. Curr. Oncol. 27, S124–S131. https://www.mdpi.com/1718-7729/27/12/5117 Mugnaini, E.N., and Ghosh, N. (2016). Lymphoma. Prim. Care 43, 661–675. https://www.sciencedirect.com/science/article/abs/pii/S0095454316300525?via%3Dihub Simpson, E., and Dazzi, F. (2019). Bone Marrow Transplantation 1957-2019. Front. Immunol. 10, 1246. https://www.frontiersin.org/articles/10.3389/fimmu.2019.01246/full Sterner, R.C., and Sterner, R.M. (2021). CAR-T Cell Therapy: Current Limitations and Potential Strategies. Blood Cancer J. 11, 69. https://www.nature.com/articles/s41408-021-00459-7 Tsao, L.-C., Force, J., and Hartman, Z.C. (2021). Mechanisms of Therapeutic Antitumor Monoclonal Antibodies. Cancer Res. 81, 4641–4651. https://aacrjournals.org/cancerres/article/81/18/4641/670332/Mechanisms-of-Therapeutic-Antitumor-Monoclonal


Visual Sources

Cover Image: What are Early Symptoms of Blood Cancer? (2023). [Image]. Kymera Medical. Retrieved June 29th, 2023, from https://kymeramedical.com/what-are-early-symptoms-of-blood-cancer/# Figure 1. Blood cancer - Types, symptoms, causes and its treatment (2023) [Image]. PW. Retrieved June 29th, 2023, from https://www.pw.live/biology-articles/blood-cancer Figure 2. Blood cancer symptoms and signs (2023) [Image]. Blood Cancer UK. Retrieved June 29th, 2023, from https://bloodcancer.org.uk/understanding-blood-cancer/blood-cancer-signs-symptoms/ Figure 3. Current available treatment strategy for blood cancer. Garg (2021). [Image]. Advanced drug delivery systems in blood cancer. Academic Press. Retrieved June 29th, 2023, from https://www.sciencedirect.com/science/article/abs/pii/B9780323855037000080?via%3Dihub



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