Lymphoma is the most common type of blood cancer. Specifically, lymphoma is a cancer that affects lymphocytes, which are a type of white blood cell. Lymphocytes travel through the blood and lymphatic system to defend the body against foreign invaders like bacteria and viruses. Lymphomas usually develop when a change, or mutation, occurs within a lymphocyte, causing the abnormal cell to replicate faster than, or live longer than, a normal lymphocyte. Like normal lymphocytes, cancerous lymphocytes can travel through the blood and lymphatic system and spread and grow in many parts of the body, including the lymph nodes, spleen, bone marrow, and other organs.
Three major categories of cancers that affect lymphocytes are: Hodgkin Lymphoma (HL): There are five types of HL, an uncommon form of lymphoma that involves the Reed-Sternberg cells. Approximately 9,000 people are diagnosed with HL in the United States each year.
Non-Hodgkin Lymphoma (NHL): There are more than 90 types of NHL, some of which are more common than others. Any lymphoma that does not involve Reed-Sternberg cells is classified as non-Hodgkin lymphoma. Approximately 80,000 people are diagnosed with NHL each year in the United States.
Chronic Lymphocytic Leukemia/Small Lymphocytic Lymphoma (CLL/SLL): Chronic lymphocytic leukemia (CLL) and small lymphocytic lymphoma (SLL) are forms of non-Hodgkin lymphoma (NHL) that arise from B lymphocytes. CLL/SLL are the same disease with slightly different manifestations. Where the cancerous cells gather determines whether it is called CLL or SLL. Leukemic cells develop because of a change that takes place in the cell’s DNA. Approximately 19,000 people are diagnosed with CLL/SLL in the United States each year.
According to the Lymphoma Research Foundation, more than 100,000 people are diagnosed with lymphoma each year and there are nearly one million in the U.S. living with, or in remission from, lymphoma. Overall, non-Hodgkin's lymphoma is the fifth most common cancer affecting adults in the United States. Hodgkin's lymphoma (HL), also known as Hodgkin's disease, represents about 10 percent of all lymphomas.
According to American Cancer Society statistics, approximately 8,830 new cases of HL will be diagnosed in the United States in 2021, and 960 people will die of the disease. Non-Hodgkin's lymphoma is much more prevalent, with an estimated 81,560 new cases and 20,720 deaths in 2021.
Treatment options for lymphoma include chemotherapy and radiation therapy. Effective treatment depends on an accurate assessment of the location and extent of disease at the time of diagnosis, as well as how the patient responds to treatment.
Molecular imaging has become an essential tool in the diagnosis, evaluation and treatment of patients with lymphoma.
The most commonly used molecular imaging technique for diagnosing and treating lymphoma is positron emission tomography (PET) scanning and PET in conjunction with computer-aided tomography (CT) scanning (PET-CT). Non-Hodgkin lymphoma patients who do not respond to chemotherapy treatment may undergo radioimmunotherapy (RIT).
PET involves the use of an imaging device (PET scanner) and a tiny amount of radiotracer that is injected into the patient’s bloodstream. A frequently used PET radiotracer is fluorodeoxyglucose (FDG), which the body treats like the simple sugar glucose. It usually takes between 30 and 60 minutes for the FDG distribution throughout the body to become fixed. A CT is also obtained on the same machine so the FDG and CT scans can be fused together and compared.
Physicians use PET-CT studies to:
For the diagnosis and treatment of lymphoma, PET-CT scans:
In a healthy immune system, the job of some white blood cells is to find invading organisms such as bacteria and viruses. The white blood cell makes a protein called an antibody that searches for a specific part on the invading cell called an antigen. The antibodies stick to the invading cell and cover the outside, which tells other white blood cells to kill it.
In immunotherapy, scientists make monoclonal antibodies in a laboratory that find and stick to the antigen on certain types of lymphoma. In RIT, the monoclonal antibody is paired with a radioactive material. When injected into the patient’s bloodstream, the antibody sticks to the lymphoma cancer cells, allowing a high dose of radiation to be delivered directly to the cancer and less radiation to normal tissues. Following RIT, a patient’s blood levels are checked weekly until levels return to normal.