Abstract P091

Characteristic of patients with a positive end of treatment PET or experiencing early relapse despite interim PET negativity: analysis from the EORTC-LYSA-FIL H10 trial.

Introduction: Assessment with early positron emission tomography (ePET) is an important predictor of outcome in both limited and advanced stages. The EORTC-LYSA-FIL 20051 H10 trial included patients with untreated favourable and unfavourable localized stage HL patients. The H10 trial was designed to established whether in ePET negative patients (after two cycles of ABVD) radiotherapy could be safely omitted. The aim of this analysis is to evaluate the clinical characteristics and outcome of the subset of patients who were ePET negative but had either a positive end-of-treatment (EoT) PET or experienced early relapse. regardless of treatment arm.

Methods: We evaluated all patients who had a negative ePET in both the standard and experimental arms. Considering the accrual period of the study population, October 2006 and July 2009, the evaluation of the response at EoT was done according to the 1999 Cheson criteria. Very few patients had been evaluated with an EoTPET. We compared the characteristics of patients with negative ePET that maintained in remission with patients with negative ePET but who had early treatment failure. Early treatment failure was defined as either a positive EoT PET or progressive disease or start of new treatment within 6 months of EoT.

Results: Of 1925 eligible patients 1402 had a negative ePET. Of these, 1064 (76%) achieved a CR/CRu and 59 (4.2%) had early treatment failure. The remaining 279 patient with a partial response did not progress or start second line treatment. By comparing the characteristics of those who maintained in remission versus early relapses we identified significant differences and a multivariate logistic regression analysis showed that stage II with an OR of 2.67 (95% CI 1.54-4.63) and bulky disease defined by MT ratio with an OR 2.24 (95% CI 1.51-3.33) are associated with worse outcome. The overall survival analysis showed that considering patients with an ePET negative early relapse had a significantly worse OS (86%) versus patients maintaining in remission (97%, p <.001). Survival was not significantly different among patients with an early relapse and a positive interim PET (86% vs 89%).

Conclusions: While a negative ePET is associated with a favorable prognosis in early stage HL, a small subgroup of patients experience early relapse with stage II disease and MT ratio >0.35 as independent risk factors for early relapse. In concordance with data on patients in advanced stage HL, early relapse among ePET