Attending Physician and Investigator in the Metabolism Branch at the National Cancer Institute
When is scanning necessary and why?
Scanning is used at several different points to assess the areas of disease that are present. It's used at initial diagnosis to "stage a patient," which means to determine how extensive the disease is or how far it has spread. Once a patient has started treatment scanning is used to assess how effective the treatment is and if it's working well. Scanning is also used at the completion of treatment to assess if the patient had a complete response to therapy. Lastly, scanning is used in the follow-up period, which can go on for a number of years after the completion of therapy.
Which are the most typical scans used for detecting Hodgkin lymphoma?
For patients with Hodgkin lymphoma, the two main types of imaging performed are computerized tomography scans (CAT or CT) and positron emission tomography scan (PET). The CT scan is the most common and uses computer processing to combine a series of X-ray views taken from many different angles. This creates cross-sectional images throughout the body. The PET scan involves giving fluorodeoxyglucose (FDG), which is a radioactive molecule attached to glucose. The PET scan allows us to assess the activity of the abnormal area. The CT scan identifies which areas are abnormal, but the PET scan can distinguish between normal metabolism and abnormal metabolism.
For patients with newly diagnosed Hodgkin lymphoma, CT scans are typically used. A PET scan can be a very helpful adjunct to the CT scan and is often performed in addition. While the CT scan is the gold standard, the PET scan is useful for detecting smaller lesions that the CT scan might not detect.
What is the accuracy of scans, especially regarding a Hodgkin lymphoma diagnosis?
You can't make a lymphoma diagnosis based on a scan. You need to have tissue from a biopsy and make a histological or pathological diagnosis of lymphoma. The scans can certainly suggest that you have lymphoma but cannot make a diagnosis. With Hodgkin lymphoma, there are certain distributions of disease that are more common so there can be a high degree of suspicion that a patient has Hodgkin lymphoma but you can never determine it without doing a biopsy.
What should a patient know going into a scan?
A patient should understand what the scan involves. With a CT scan patients get something called contrast. There's oral contrast and intravenous contrast and these are given before the scan. The scan itself is usually a 20 or 30 minute procedure. The PET scan is a little different because patients need to have an injection of FDG (fludeoxyglucose) before the scan. This is a type of radiopharmaceutical agent.
What should a patient know after their scan is read?
It's depends on the time point of the scan in relation to therapy - whether it is at initial diagnosis, during therapy, at the end of treatment, or in follow-up. If it's an initial scan, you want to know how extensive the Hodgkin lymphoma is and if there is disease above and below the diaphragm because that impacts what staging
As a patient goes through treatment, they have a scan for response assessment in the middle of treatment. At that point, you want to know how improved your scan is, how decreased the lesions are compared to how they were at initial diagnosis. If you have a PET scan in the middle of treatment, which is a little controversial, you want to know if the activity of the lesions has decreased and if there is any activity at all. You may have a negative PET scan during treatment.
At the end of treatment, you want to know if there is any disease remaining. Is there any activity on the PET scan? Often with Hodgkin lymphoma, there will be abnormalities on the CT scan which may remain following treatment, even when there is no active disease present. The PET scan is very important in determining if that tissue is what's called PET-avid/positive, or not. Often with Hodgkin lymphoma, patients who have a very good response may still have persistent CT abnormalities, but the PET scan is completely negative which is a very common scenario.
In follow-up, CT scans are done but PET scans are not. From a patient's perspective, you want to know that there has been no recurrence of the Hodgkin lymphoma and that there aren’t any lymph nodes or abnormalities on the follow-up CT scans.
Are there any concerns or considerations about scanning, particularly with Hodgkin lymphoma patients and survivors?
That’s a very good question and something patients are very concerned about at the moment. There is a radiation risk when you have a CT scan. This is particularly important in the follow-up setting when patients have finished treatment and had a good response to the treatment. In the ensuing years, they continue to have scanning; and that is associated with exposure to radiation during each scan. With more and more scans, patients are exposed to more and more radiation. There is a very minimal risk a patient that has had a lot of CT scans over several years can develop a tumor or a malignancy as a result of the radiation the risk is very, very low; but it is still a concern. In that respect, as researchers in this field, when we're developing treatments and planning new strategies, we are trying to reduce the frequency of scanning and investigate new ways of monitoring disease.
There also are some new CT scanning machines that reduce radiation exposure compared to older ones or conventional ones. That's important for the future for patients.
Additionally patients are familiar with PET scans because they are now done at many points during treatment, but they can often be falsely positive. There are many things apart from lymphoma that can cause a PET scan to be abnormal and physicians should always take this into consideration when performing and interpreting scans. Patients need to consider that as well, just because the PET scan is positive doesn't always mean that there is active lymphoma present.
How are you involved with the Lymphoma Research Foundation (LRF)?
I serve on the Scientific Advisory Board for LRF. Earlier this year, I was a mentor at the first ever LRF Clinical Research Mentoring Program, which is focused on junior researchers interested in careers as lymphoma researchers. I also partake in LRF education programs and last year spoke about scanning at LRF's North American Education Conference on Lymphoma held in New York. I also talk about new advances in lymphoma treatment at local (DC metro area) LRF information meetings.