PET Response-Adapted Treatment in Hodgkin Lymphoma

Abstract

The present review will focus on the issue of interim PET scan intended as surrogate test for chemosensitivity in Hodgkin lymphoma (HL). When performed early during treatment, PET scan is able to predict the final treatment outcome with variable accuracy, depending on HL tumour burden. In early-stage disease, interim PET shows a very high sensitivity and negative predictive value, while specificity and positive predictive value are only moderate, due to a substantial number of false-positive studies. In advanced-stage disease, a better positive predictive value has been reported, at the partial expense of the negative predictive value, which proved suboptimal, due to a non negligible percentage (5–10 %) of cases experiencing treatment failure despite a negative interim PET scan. The latter transformed, in the last decade, from a simple imaging technique to a prognostic tool indissoluble from HL therapeutic strategy. As a consequence, several PET response-adapted strategies have been proposed in clinical trials; some of them already concluded, while others are still ongoing. In early-stage lymphoma, two phase II trials explored whether treatment de-escalation by omitting involved-field radiation could be safely offered in interim PET-negative patients, without compromising the treatment efficacy, with opposite conclusions. In advanced-stage disease, most trials have been addressed to explore the efficacy of escalating treatment in interim PET-positive patients after few courses of ABVD treatment, while two others are still ongoing aimed at assessing treatment de-escalation in patients with a negative interim PET scan after two courses of BEACOPP escalated.