The Impact of PET/CT Staging on the Incidence of Late Hodgkin Lymphoma Relapse for Patients Treated with Limited Radiation Fields

Abstract

A recent pooled analysis1 reported a risk of late Hodgkin lymphoma relapse (LR) between 5-20 years after treatment of early stage classical Hodgkin lymphoma (HL) treated with involved field radiotherapy (IFRT). PET/CT staging was not standardly performed in the included trials, but our institution routinely performed PET/CT in this era. This study aims to assess the impact of PET/CT staging on the incidence of LR for patients with early stage HL treated in the IFSRT era. We performed a retrospective assessment of all patients treated for stage I-II HL with multiagent chemotherapy followed by involved field or involved site radiotherapy (IFSRT) from 2000 to 2011 at our institution. The German Hodgkin Study Group (GHSG) risk stratification criteria system was utilized. Patients routinely underwent bone marrow biopsy and PET/CT scan for staging. Overall (OS) and event-free survival (EFS) was estimated using the Kaplan-Meier method. Any recurrence or death was considered an event. Incidence of relapse was estimated using the cumulative incidence function. LR was defined as any relapse occurring ≥ 5 years from initial diagnosis. A total of 134 patients were included. Median age was 34 years (range, 4-77). Stage: 15% IA, 1% IB, 66% IIA, and 17% IIB. 60% were unfavorable risk. 77% had disease in the mediastinum. 109 patients (81%) completed a staging PET/CT. ABVD (93%) was the most commonly prescribed chemotherapy. Radiation dose and fractionation ranged from 20-40 Gy in 1.5-2 Gy fractions. The median follow up for all patients and those staged with PET/CT was 8.1 and 8.2 years respectively. A total of 27% have more than 10 years of follow up. OS for the entire cohort at 5, 10 and 15 years was 97.5%, 96.0%, and 88.9% respectively. EFS for the entire cohort at 5, 10, and 15 years was 96.6%, 94.8%, 85.2% respectively. Only 3 of 134 patients experienced a relapse and of these 2 have died. Two of the 3 patients who relapsed did not have a staging PET/CT. Relapses occurred at 11, 18, and 30 months after treatment, corresponding to a cumulative incidence of relapse at 3 years of 2.6%. No late relapses were observed (>5 years). Continued decline in OS and EFS beyond 5 years was due to death from unrelated causes and was limited to patients over the age of 70 years at initial HL diagnosis. 5 patients developed a non-skin secondary malignancy at a median time of 6.3 years after diagnosis. Of these malignancies, 1 was fatal (acute myeloid leukemia). Based on the findings of Brockelmann et al., the anticipated incidence of late relapse should have been between 2-5%, however in this cohort with a majority of patients undergoing staging PET/CT, there were no late relapses. Our results provide support for further study of the hypothesis that the use of PET/CT at the time of initial staging may be associated with a lower risk of late relapse. 1. Brockelmann et al. Late Relapse of Classical HL: An Analysis of the GHSG HD7 to HD12 Trials. JCO. 2017.