Page 239 - 18F-FDG PET as biomarker in aggressive lymphoma; technical and clinical validation

Summary, discussion and future perspectives
current chemotherapy based escalation strategies did not overcome treatment resistance [8-10].
In Chapter 3 a systematic review and meta-analysis of the predictive value of visual assessment of interim [18F]FDG PET focusing on DLBCL patients summarizes the results of twenty published and eligible studies without treatment adaptation based on the interim [18F]FDG PET result [11]. We concluded that there is indeed predictive value of interim [18F]FDG PET for 2-year progression- free survival (pooled hazard ratio of 3.13). Negative predictive values exceeded 80%, but positive predictive values (ranging from 20 to 74% between studies) were too low to allow for a risk stratified treatment approach in clinical practice. Additional subgroup analyses on differences in timing of interim [18F]FDG PET, patient subgroups, PET techniques and PET response criteria were limited by lack of information, heterogeneity and small sample sizes.
Based on the 2 chapters in this part we concluded that there is predictive value of interim [18F]FDG PET in both HL and DLBCL. Nowadays, interim [18F]FDG PET indeed plays an important role in the “state of the art” treatment of HL. For DLBCL, the role of interim [18F]FDG PET as a biomarker of response was still unclear.
Part II Technical validation of PET in lymphoma
In Chapter 4 the interobserver agreement of the Deauville 5-point scale for both interim [18F]FDG PET and end-of-treatment [18F]FDG PET in DLBCL patients included in the HOVON-84 study was assessed [12]. The central review of the study was performed by 2 nuclear medicine physicians (from a pool of 10). We concluded that the overall agreement was 87.7% and 91.7% for interim and end-of-treatment [18F]FDG PET, respectively. The corresponding positive agreement (i.e. the probability that if one reviewer assigns a positive score, a second reviewer scores positive as well) was 73.7% and 76.3%. Based on these results, we recommended to perform dual reads for treatment evaluation in clinical practice (e.g. within multidisciplinary tumor board meetings) and for trials to perform central review procedures. Especially sites of extranodal lymphoma involvement in the gastrointestinal tract, Waldeyer’s ring, skeletal system and spleen led to a
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