130IN - Pet-Based Response Criteria in Lymphoma: Current Status and Future Directions

Abstract

ABSTRACT PET-based response criteria in lymphoma: Current status and future directions 18FDG-PET/CT is now the more valuable imaging tool for response assessment in Hodgkin lymphoma (HL), diffuse large B cell lymphoma (DLBCL) and Follicular lymphoma (FL) by its property to image the residual metabolic activity irrespective of residual volume. In 2009 the Deauville Criteria (DC) were proposed for interim PET iPET and recently the Imaging working group of the International Conference on Malignant Lymphoma decided to use the DC for interim and end treatment reporting. DC are as follows: 1. no uptake; 2. uptake ≤ mediastinum (MBP); 3. uptake > mediastinum but ≤ liver; 4. uptake moderately higher than liver; 5. uptake markedly higher than liver and/or new lesions; X new areas of uptake unlikely to be related to lymphoma. The use of these criteria for iPET reporting has been validated in HL, DLBCL and FL and confirmed the predictive value of iPET. With a score ≥ 4 for positivity Biggi has reported in HL after 2 cycles of ABVD, a 3-y failure-free survival of 28% for PET + ve versus 95% for PET-ve patients (P = 0.0001). Itti has shown in DLBCL a 3-year progression-free-survival (PFS) of 59% in PET2 + ve patients vs. 81% (71–91%) in PET2-ve patients after two cycles of R/CHOP or ACVBP (P = 0.003). At end treatment complete metabolic response (CMR) is defined for score 1-3 under standard treatment. The validity at end treatment of using DC has been recently confirmed in prospective studies in 106 patients (LYSA) with follicular lymphoma, 115 patients with PMLBCL from the IELSG-26 study and 141 patients with DLBCL from the SAKK38/07 study. For good reporting base line PET is mandatory. DC suffers some limitations: visual reporting biased by the contrast and for iPET DC reflects the response to treatment at one time point, but misses the kinetics of tumor destruction. DSUVmax technique (relative variation between the SUVmax of the lesion with the maximum uptake at base line and the SUVmax of the residual site after one or more cycles of treatment) expresses this kinetics. Few studies have shown its superiority to predict outcome in DLBCL and HL over the visual DC. Future directions will combine visual and quantitative criteria, molecular markers or baseline metabolic tumour volume at staging with tumour response under treatment to define new prognostic indices. Disclosure: The author has declared no conflicts of interest.