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Lymphoma is a cancer of the lymphatic system, which includes the lymph nodes, spleen, thymus, and bone marrow. There are two major types of lymphoma: Hodgkin’s lymphoma, also known as Hodgkin’s disease (HD) and non-Hodgkin’s lymphoma (NHL).

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.

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).

What is PET?

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.


How is PET used for lymphoma?

Physicians use PET-CT studies to:

  • diagnose and stage: by determining the exact location of a tumor, the extent or stage of the disease and whether the cancer has spread in the body.
  • plan treatment: by selecting the best therapy based on the unique biology of the cancer and of the patient.
  • evaluate the effectiveness of treatment: by determining the patient’s response to specific drugs and ongoing treatment. If the treatment is not working well enough, then PET can help doctors decide whether to change the type of treatment early on.
  • manage ongoing care: by early detection of the cancer coming back.


Advantages of PET

For the diagnosis and treatment of lymphoma, PET-CT scans:

  • are the most accurate single test to evaluate lymphoma.
  • have resulted in a change in treatment plan for more than one-third of lymphoma patients registered in the National Oncologic PET Registry (NOPR).
  • are recommended for the diagnosis and re-staging and follow-up of most types of lymphoma by cancer experts, including the National Comprehensive Cancer Network.
  • provide the most accurate means of detecting lymphoma recurrence. Using PET-CT scans, physicians are able to determine the difference between scar tissue produced by treatment and active lymphoma before this would be revealed by CT alone.


What is radioimmunotherapy (RIT)?

Radioimmunotherapy(RIT) is a personalized cancer treatment that combines radiation therapy with the precise targeting ability of immunotherapy, a treatment that copies the action in the body’s immune system.

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.