There are two main types of lymphoma: Hodgkin’s lymphoma or Hodgkin’s disease, identified in 1832 by Dr. Thomas Hodgkin, and non-Hodgkin’s lymphoma. Because lymph tissue is found in many parts of the body, lymphoma can start nearly anywhere. The lymph nodes become enlarged and the cancer can spread through the lymph system. Each year, there will be about 9,000 new cases of Hodgkin’s disease and about 72,000 cases of non-Hodgkin’s lymphoma diagnosed, according to the American Cancer Society.
Hodgkin’s disease and non-Hodgkin’s lymphoma are different diseases that both arise from the lymph node tissues in the body. In fact, there are many, many types of non-Hodgkin’s lymphoma. The different types can be distinguished from one another by looking at the cells under a microscope. Regardless of the type of cell, early diagnosis and appropriate treatment is the key to a patient’s long term well-being.
Atlanta: American Cancer Society; 2015
There are no screening tests that find Hodgkin’s disease or non-Hodgkin’s lymphoma early in its course and some people with the disease show no symptoms at all. The signs and symptoms of lymphoma may vary depending on the location of the lymph tissue that is involved with the disease. Since enlarged lymph nodes are the primary sign, the diagnosis of lymphoma may be delayed because enlarged lymph nodes commonly occur with infections. Doctors often observe swollen nodes over a period of weeks to look for changes or reductions in size. Some of the most common early symptoms of lymphoma may be:
In addition to the local signs related directly to the enlarged lymph nodes, patients may also experience:
If the lymph node does not resolve on its own and doctors suspect lymphoma, they will most likely perform a physical exam and a biopsy, where either a small piece of the node or, more commonly, the entire node is removed for examination under the microscope. PET scans can help doctors select a site for biopsy when the first suspected site is not easily accessible. PET scanning is also used by physicians to characterize the extent of lymphoma spread.
PET scans can help physicians select an appropriate site to biopsy.
Treatment options, as well as the outlook for recovery, depend on determining both the exact type and the stage of lymphoma. Once identified, the physician performs a biopsy on the suspected lesion, and by examining the cells under a microscope can determine the type of lymphoma. Proper staging of the location and extent of the tumor is an important step before deciding on the most appropriate treatment. Physicians utilize PET scans to provide staging information and to help detect disease that may have spread beyond the lymph nodes to other areas such as bone marrow, liver or spleen. In addition to providing essential staging information, the initial PET scan provides a baseline for subsequent evaluation of whether the therapy was effective.
A number of other diagnostic tests used to gather information for staging, may be performed in addition to the PET scan and a sentinel node biopsy. These may include:
Hodgkin’s lymphoma is usually treated with chemotherapy and/or radiotherapy, depending on the stage and cell-type of the disease. Non-Hodgkin’s lymphoma patients are usually treated with chemotherapy; radiation, alone or in combination with chemotherapy, is used less often. Highly specific monoclonal antibodies directed at lymphoma cells are used for initial treatment and recurrence of some types of non-Hodgkin’s lymphoma, as are antibodies linked to a radioactive atom. High-dose chemotherapy with stem cell transplant and low dose chemotherapy with stem cell transplant are options if non-Hodgkin’s lymphoma persists or recurs after standard treatment.
Proper staging of the location and extent of the tumor is the first step in appropriate treatment.
Atlanta: American Cancer Society; 2015
Once treated, patients are often restaged to determine the effectiveness of the treatment. A follow-up whole-body PET scan can help evaluate whether the therapy was effective and can be particularly useful in helping the physician detect residual disease.
Before PET, it was extremely difficult to monitor patients to see if the lymphoma had returned. Multiple CT scans would have to be done to capture images of the whole body and anatomical imaging merely identified changes in tumor size. In lymphoma, the tumor’s glucose metabolism falls very rapidly after effective chemotherapy and PET imaging can detect an increase or decrease in glucose utilization. Often, lymphoma tumors are large in diameter and do not immediately shrink to normal size after treatment. Physicians utilize PET imaging to characterize a residual mass, or determine if active tumor cells remain within the scar tissue.
Early studies have shown that PET may also identify patients who are more likely to achieve remission and less likely to relapse, by showing a characteristic pattern of reduction in glucose uptake in the abnormal lymph nodes half-way through and during planned chemotherapy. A negative PET scan does not mean that treatment should be stopped, but it predicts a superior outcome to a positive PET scan at mid treatment.
The treatment of lymphoma has been one of the true cancer success stories of the last 20 to 30 years. Continued improvements in chemotherapy and radiotherapy have resulted in better survival rates.
PET can be used to image tumor response to therapy and to detect recurrence in treated lesions.
PET is a noninvasive test that physicians utilize to stage the body for the presence or absence of active tumor, localize the tumor, assess the tumor response to treatment and detect recurrence in treated lesions.
PET Utilization for Lymphoma
Source: Atlas of Clinical Positron Emission Tomography by Sallie F. Barrington, Michael N. Maisey and Richard R. Wahl. Oxford University Press, Inc. New York, NY.
Oncologic PET/CT: A primer for radiologists by Stephen Humes, MD. AuntMinnie.com