Interim ¹⁸F-FDG PET in hodgkin lymphoma: Would PET-adapted clinical trials lead to a paradigm shift?

Hodgkin lymphoma (HL) is a curable disease with currently available chemotherapy regimens. Major late morbidities can potentially be avoided in most limited-stage HL patients if the treatment can be adapted to the patient's early response profile. The therapy efficacy can also be increased early during therapy in nonresponding HL patients with the addition of involved-field radiation therapy or a switch to an escalated therapy protocol, particularly in advancedstage or unfavorable-risk patients. ¹⁸F-FDG PET is a well-established surrogate for tumor chemosensitivity early during therapy. The ongoing PET-adaptive clinical trials are testing the hypothesis that a decision can reliably be made on escalating or deescalating therapy based on interim PET results. Discussed in this review is the integral role of interim ¹⁸F-FDG PET in HL, challenges, critical issues to improve its accuracy, and the observations from completed interim PET studies and ongoing PET-adaptive clinical trials.