Patients with follicular lymphoma or marginal zone lymphoma should receive radiotherapy at a dose of 24 Gy in 12 fractions and not a lower dose of 4 Gy in 2 fractions, according to the long-term follow-up results of FoRT (Follicular Radiotherapy Trial) published in Lancet Oncology.
At 43 centers in the United Kingdom, the randomized, phase 3, noninferiority trial (ClinicalTrials.gov Identifier: NCT00310167) enrolled 548 patients with follicular lymphoma or marginal zone lymphoma who needed local radiotherapy for palliative or curative intent. Patients had 614 radiotherapy target sites, most of which were for follicular lymphoma (86%) and the rest marginal zone lymphoma (14%).
Target sites were randomly assigned to treatment with 24 Gy in 12 fractions, which is the standard of care, or a lower dose of 4 Gy in 2 fractions. The study authors explained that randomization was by target site rather than patient, so an individual patient could contribute more than 1 site to the trial.
At a median follow-up of 73.8 months, treatment with 24 Gy in 12 fractions offered superior local control, with a lower number of local progression events at target sites compared with the low-dose arm (27 vs 90).
The progression-free rate was superior for the standard arm at both 2 years (94.1% vs 79.8%) and 5 years (89.9% vs 70.4%) compared with the low-dose arm, and time to progression for the low-dose arm compared with the standard arm was deemed inferior (hazard ratio, 3.46; 95% CI, 2.25-5.33; P <.0001).
“This long-term follow-up analysis of FoRT confirms the previously published results showing that 4 Gy is inferior to 24 Gy in terms of duration of local control,” wrote the study authors.
The study authors explained that because responses were seen with 4 Gy in 2 fractions, and approximately two-thirds of patients had local control for several years, the low dose schedule could be considered in patients requiring palliation or in whom definitive systemic treatment is planned.
Hoskin P, Popova B, Schofield O, et al. 4 Gy versus 24 Gy radiotherapy for follicular and marginal zone lymphoma (FoRT): long-term follow-up of a multicentre, randomised, phase 3, non-inferiority trial. Lancet Oncol. Published online February 1, 2021. doi:10.1016/S1470-2045(20)30686-0