Lymphoma is a cancer that begins in cells of the immune system, in particular in the lymph system, an interconnected network of vessels and nodes that circulate a fluid called lymph . The lymph is rich in lymphocytes, a type of white blood cells that help the body fight off infections and other diseases . Lymphoma occurs when lymphocytes become cancerous . The two main types of lymphomas are Hodgkin lymphoma (HL) and non-Hodgkin lymphomas (NHL), and are differentiated by the type of lymphocytes affected and their appearance under the microscope [1, 3].
Non-Hodgkin lymphoma (NHL) is a heterogenous group of cancers of the lymphatic system, characterized by overproduction and accumulation of immature white blood cells called lymphocytes. NHL is classified in B-cell NHL and T-cell NHL depending on the type of lymphocytes affected [1, 3, 4] (Figure 1). These cancerous lymphocytes can travel to and accumulate in many parts of the body, including in the lymph nodes, bone marrow, spleen or other organs, affecting the normal function of the lymphatic system or the organ in which they are growing [1, 3]. NHL can further be sub-classified based on the pathologic appearance, the chromosome features and the presence of certain proteins on the surface of the cells [1, 4].
Figure 1: Schematic of normal blood cells and NHL development
Treatment for NHL depends of its sub-type, how aggressively the cancer cells multiply, how immature they are (grade), the extent to which it has spread over the body (stage) as well as the patient’s general health and age . The main treatment strategies include chemotherapy, radiotherapy and, in some cases, surgery . High dose chemotherapy with a stem cell transplant may also be used in some patients to try to increase the chance of curing NHL .
While treatment advances in the last three decades have improved NHL response rates, most patients eventually relapse or are refractory to these therapies . Treatment options for these patients include salvage therapy and, in some cases, stem cell transplants . However, treatment mortality for these therapies is high and the survival benefit is limited [6, 7].