End-of-treatment but not interim PET scan predicts outcome in nonbulky limited-stage Hodgkin's lymphoma

Background: Early interim positron emission tomography (PET) scans appear powerfully predictive of outcome in Hodgkin's lymphoma (HL), particularly in advanced-stage disease where it has been predominantly studied. The prognostic value of interim PET in limited-stage patients with nonbulky disease has not been well established. Patients and methods: Ninety-six patients with nonbulky limited-stage HL were identified who had interim and end-of-treatment PET scans. Response rate, overall survival (OS), and progression-free survival (PFS) were calculated. Results: Four-year PFS and OS for the entire cohort were 88% and 97%, respectively. Interim PET did not predict outcome, with PFS in positive and negative patients 87% versus 91% (P = 0.57), respectively. End-of-treatment PET result was predictive of outcome, with PFS of 94% in end PET-negative patients versus 54% in end PET-positive patients (P < 0.0001). Four-year OS was 100% in end PET-negative patients and 84% in end PET-positive patients (P < 0.0001). Conclusions: Interim PET scans were not predictive of outcome, compared with scans carried out at completion of therapy. End-of-treatment PET was highly predictive of PFS and OS, regardless of interim PET result. In this low-risk patient population, even patients with interim positive PET scans show a favorable prognosis.