Definitive radiotherapy for localized follicular lymphoma staged by 18F-FDG PET-CT: a collaborative study by ILROG

Jessica L. Brady, Michael S. Binkley, Carla Hajj, Monica Chelius, Karen Chau, Alex Balogh, Mario Levis, Andrea Riccardo Filippi, Michael Jones, Michael Mac Manus, Andrew Wirth, Masahiko Oguchi, Anders Krog Vistisen, Therese Youssef Andraos, Andrea K. Ng, Berthe M.P. Aleman, Seo Hee Choi, Youlia Kirova, Sara Hardy, Gabriele Reinartz, Hans T. Eich, Scott V. Bratman, Louis S. Constine, Chang-Ok Suh, Bouthaina Dabaja, Tarec C. El-Galaly, David C. Hodgson, Umberto Ricardi, Joachim Yahalom, Richard T. Hoppe and N. George Mikhaeel

Key points

  • Outcome following radiotherapy for stage I and localized stage II follicular lymphoma after PET-CT staging is better than historical series.

  • More than two-thirds of patients remain in remission at 5 years and most relapses occur in distant sites.


Radiotherapy (RT) can be curative in patients with localized follicular lymphoma (FL), with historical series showing a 10-year disease-free survival of 40-50%. As 18F-FDG PET-CT upstages 10-60% of patients compared to CT, we sought to evaluate outcomes in patients staged by PET-CT, to determine if more accurate staging leads to better patient selection and results. We conducted a multicenter retrospective study. Inclusion criteria were: RT alone for untreated stage I-II FL (grade 1-3A) with dose equivalent ≥24 Gy, staged by PET-CT, age ≥18 years, and follow up ≥3 months. Endpoints were freedom from progression (FFP), local control, and overall survival (OS). FFP and OS were estimated with Kaplan-Meier, and uni- and multivariable analyses of prognostic factors performed with Cox Regression. 512 patients treated from 2000-2017 at 16 centres were eligible for analysis. Median age was 58 years (range 20-90). 410 patients (80.1%) had stage I disease. Median RT dose was 30 Gy (24-52). Median follow up was 52 months (3.2-174.6). 5y-FFP and OS were 68.9% and 95.7%. For stage I, 5y-FFP was 74.1%, vs 49.1% for stage II (p<0.0001). 8 patients relapsed infield (1.6%).4 had marginal recurrences (0.8%) resulting in local control rate of 97.6%. On multivariable analysis, stage II (HR=2.11, 95%CI=1.44-3.10) and BCL2 expression (HR =1.62, 95%CI 1.07-2.47) were significantly associated with less favorable FFP. Outcome after RT in PET-CT staged patients appears to be better than in earlier series, particularly in stage I disease, suggesting that the curative potential of RT for truly localized FL has been underestimated.

  • Submitted April 18, 2018.
  • Accepted October 31, 2018.