Successful Long-Term Outcomes in Patients with Lymphoma Achieving Only Partial Response on [¹⁸f]FDG-PET Prior to Allogeneic Transplant

Introduction

Allogeneic hematopoietic stem cell transplant (HSCT) is an option in patients with lymphoma with refractory or multiply relapsed disease. Consensus remains to be reached on the prognostic value of positron emission tomography using 18-fluorodeoxyglucose ([¹⁸F]FDG-PET) prior to allogeneic HSCT.

Methods

Patients having undergone allogeneic HSCT for lymphoma between 2004 and 2013, who also had pre-transplant PET assessment, were identified. Patient demographic and disease-related data was collected retrospectively from electronic patient records. Contemporaneous PET-CT reports were used to document disease status prior to HSCT. Kaplan-Meier analysis was used to assess the impact of categorical variable on patient outcome.

Results

44 eligible patients were identified. 30 (68.2%) were male, with a median age of 38 years (range 14-68). 23 (52.3%) had Hodgkin lymphoma, six (13.6%) follicular lymphoma, five (11.4%) mantle cell lymphoma, and three had (6.8%) diffuse large B-cell lymphoma; other B and T-cell lymphomas accounted for the remainder. 39 patients (88.6%) had advanced stage disease, and 32 (72.7%) had received at least four prior lines of chemotherapy or radiotherapy. 20 (45.5%) had had a prior autograft. At pre-transplant staging using PET, 18 (40.9%) achieved a complete response (CR), seven (15.9%) a very good partial response, and 12 (27.3%) a partial response (PR). Two patients (4.5%) had stable disease and five (11.4%) had progressive disease going into transplant. Overall survival (OS) at five years was 38.9%, and progression-free survival (PFS) 35.7%. There was no significant impact of patient age, gender, disease, disease stage or number of lines of previous therapy on OS or PFS. Overall, patients with less than CR on pre-transplant PET showed a trend towards an inferior PFS (48% vs 24% at 3 years, p=0.092), but there was no impact on OS. In particular, patients with PR going into allograft showed OS (55% at three years) and PFS (42% at three years) comparable with those in CR (51% and 48% at three years respectively). However, analysis of disease progression (treating death in remission as a competing risk) showed that those with less that CR on pre-transplant PET had a significantly higher risk of disease progression than those in CR (46% vs 8%, p=0.0068). Non-relapse mortality was 19.5% at 1 year and 39% at 3 years.

Conclusion

Although a complete response is highly desirable prior to allogeneic transplant in any patient with lymphoma, our study shows that those showing only a partial response to prior therapies may still have a successful long-term outcome. Considering that such patients invariably relapse following autologous transplant, PET may have a role in deciding between autologous and allogeneic transplant in patients who fail to achieve either a CR or VGPR. However, such a question needs to be answered with prospective data.