Treatment and prognosis of stage I follicular lymphoma in the modern era - does PET matter?

Follicular lymphoma (FL) is the most common subtype of indolent non-Hodgkin lymphoma. Patients with stage I disease are usually treated with radiotherapy (RT). In previous studies, mostly from the pre positron emission tomography-computed tomography (PET-CT) era, the 5 year progression-free survival (PFS) and overall survival (OS) rates of stage I disease were 60-80% and 80-93%, respectively. This study retrospectively evaluated the outcome of stage I FL which was treated with involved field RT in the PET-CT era between 2002 and 2015. Ninety-one patients were enrolled. Five year PFS and OS rates were 73% and 97%, respectively. Relapse occurred in 19 (21%) patients, 74% occurring outside the radiation field. In conclusion, PET-CT staging of clinical stage I FL may contribute to the improved prognosis in patients treated with RT compared to historical cohorts, possibly due to better identification of "genuine" stage I disease.