End of chemotherapy response assessment

Defining complete response. The definition of complete response may vary by cooperative group or protocol.

Defining complete response. The definition of complete response may vary by cooperative group or protocol.

The International Working Group (IWG) defined complete response for adults with Hodgkin lymphoma in terms of complete metabolic response as assessed by 18F-FDG PET, even when a persistent mass is present.[35] These criteria were endorsed in the Lugano classification, with the recommendation for a 5-point scale to assess response.[6,36] COG protocols have adopted this approach for defining complete response.

Defining complete response. The definition of complete response may vary by cooperative group or protocol.

Previous studies have varied in the use of findings from the clinical examination, anatomical imaging, and functional imaging to assess response. Although complete response can be defined as absence of disease by clinical examination and/or imaging studies, complete response in Hodgkin lymphoma trials is often defined by a greater than 80% reduction of disease and a change from initial positivity to negativity on functional imaging.[37] This definition is necessary in Hodgkin lymphoma because fibrotic residual disease is common, particularly in the mediastinum. In some studies, such patients are designated as having an unconfirmed complete response.

Timing of PET scanning after completing therapy. Timing of PET scanning after completing therapy is an important issue.

Timing of PET scanning after completing therapy. Timing of PET scanning after completing therapy is an important issue.

For patients treated with chemotherapy alone, PET scanning is ideally performed a minimum of 3 weeks after the completion of therapy, while patients whose last treatment modality was radiation therapy should not undergo PET scanning until 8 to 12 weeks postradiation.[35]

Screening frequency and overscreening.

Screening frequency and overscreening.

A COG study evaluated surveillance CT and detection of relapse in intermediate-stage and advanced-stage Hodgkin lymphoma. Most relapses occurred within the first year after therapy and were detected based on symptoms, laboratory, or physical findings. The method of detection of late relapse, whether by imaging or clinical change, did not affect overall survival. Routine use of CT at the intervals used in this study did not improve outcome.[38] Other investigations have supported the concept of reduced frequency of imaging.[39,40]

Screening frequency and overscreening.

Caution should be used in diagnosing relapsed or refractory disease based solely on anatomical and functional imaging because false-positive results are not uncommon.[41-43] Consequently, pathological confirmation of refractory or recurrent disease is recommended before modification of therapeutic plans.