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Blood. 2018 Nov 16. pii: blood-2018-04-843540. doi: 10.1182/blood-2018-04-843540. [Epub ahead of print]

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

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Guy's Cancer Centre, Guy's and St Thomas' Hospital, London, United Kingdom;
Stanford Cancer Institute and Stanford University School of Medicine, Stanford, CA, United States.
Memorial Sloan Kettering Cancer Center, New York, NY, United States.
Tom Baker Cancer Center, Calgary, AB, Canada.
University of Torino, Torino, Italy.
Princess Margaret Cancer Center, Toronto, ON, Canada.
Peter MacCallum Cancer Centre, Melbourne, VIC, Australia.
Cancer Institute Hospital, Tokyo, Japan.
Aalborg University Hospital, Aalborg, Denmark.
University of Texas MD Anderson Cancer Center, Houston, TX, United States.
Dana Farber and Harvard University School of Medicine, Boston, MA, United States.
Department of Radiation Oncology, The Netherlands Cancer Institute, Amsterdam, Netherlands.
Yonsei Cancer Center, Yonsei University Health System, Seoul, Korea, Republic of.
Institut Curie, Paris, France.
University of Rochester, Rochester, NY, United States.
Munster University, Munster, Germany.
Guy's Cancer Centre, Guy's and St Thomas' Hospital, London, United Kingdom.


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.

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