Prognostic significance of mid- and post-ABVD PET imaging in Hodgkin's lymphoma: the importance of involved-field radiotherapy.

BACKGROUND Although positron emission tomography (PET) response to chemotherapy (CT) has prognostic significance in Hodgkin's lymphoma (HL), it is unclear whether patients with 2-[fluorine-18]fluoro-2-deoxy-D-glucose (FDG)-PET positivity during and/or after CT can be rendered disease free with consolidative involved-field radiotherapy (IFRT). METHODS Patients with HL treated with adriamycin, bleomycin, vinblastine and dacarbazine (ABVD)-based CT and radiotherapy (RT) at our institution from January 2000 to March 2007 were eligible. All patients had either a post-treatment PET or PET-CT before initiation of RT or a negative midtreatment PET or PET-CT. The primary end point was failure-free survival (FFS) for patients with and without residual FDG avidity after ABVD. The treatment outcome of patients with interim PET positivity during CT was also reported. RESULTS Seventy-three patients were included in this study. Twenty patients (out of 46) were PET positive on interim PET, and 13 patients (out of 73) were PET positive at the conclusion of CT. At a median follow-up of 3.4 years for surviving patients, the 2-year FFSs for patients PET-negative versus PET-positive disease after ABVD were 95% and 69%, respectively (P < 0.01). On bivariable Cox regression, post-ABVD positivity (hazard ratio 4.8, P = 0.05) was predictive of disease recurrence after controlling for bulky disease. Of the 20 patients with interim PET positivity, three recurred, with a 2-year FFS of 85%. Among the 13 patients with interim PET positivity, but became PET negative at the completion of CT, the 2-year FFS was 92%. CONCLUSION Sixty-nine per cent of patients with residual FDG avidity after ABVD were free of disease after consolidative RT, indicating a majority of patients with persistent lymphoma can be cured by sterilizing this PET-positive disease.