Use of PET Scan in Hodgkin Lymphoma

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The most recent Lugano Staging Classification system for Hodgkin and non-Hodgkin lymphomas has recommended that if a patient with Hodgkin lymphoma has a PET-CT, it is not necessary to perform a bone marrow biopsy (Cheson BD et al. J Clin Oncol. 2014;32(27):3059-3068). John Sweetenham, MD, explains this is an important step forward from a patient perspective, reducing the invasiveness of the staging methods for this disease.

During therapy, a PET scan performed after two or three cycles of chemotherapy can have prognostic significance--a negative PET scan suggests a higher probability of cure versus a positive PET scan. Similarly, the end-of-treatment PET scan is a very useful prognostic indicator--if a patient has a negative PET at the end of their primary therapy, there is an approximate 80% probability they will have a long remission. The positive predictive value of a PET is not quite as strong as the negative predictive value.

Many questions remain regarding PET, Sweetenham notes, including whether a PET scan, performed early on in the course of the treatment, should change the direction of treatment direction. For example, he adds, if the patient has a negative PET, could the amount of treatment be reduced? On the other hand, if PET-positive, can treatment be intensified to overcome resistance?

Robert Chen, MD, describes a trial that may provide answers to these questions.

In this US-based trial, patients with advanced Hodgkin lymphoma will receive two cycles of ABVD followed by an interim PET scan. If PET-negative, they will finish the standard six cycles of ABVD. However, if PET-positive, they will switch from ABVD to BEACOPP, a more intense regimen.

For patients with early-stages of disease, Anas Younes, MD, describes the UK RAPID trial approach of using interim PET scan results to adjust treatment, including incorporating a combination of modalities (Radford J, et al. Blood. 2012;120:547). Additionally, Sweetenham and Chen discuss the predictive value of a PET scan prior to transplant, but after salvage therapy.

Data from Memorial Sloan Kettering suggest that if patients are PET-negative after salvage chemotherapy, they have a better two-year progression-free survival after transplant. Whereas, if they remain PET-positive after salvage chemotherapy, they tend to have a worse long-term outcome, even after stem-cell transplant (Moskowitz CH et al. Blood. 2012;119(7):1665-1670).