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Top Line: What is the long-term control rate with 4 Gy and 24 Gy for follicular and marginal zone lymphoma?

The Study: The FoRT trial randomized patients with indolent follicular (86%) and marginal zone lymphoma receiving either radical or palliative radiation to 24 Gy in 12 fractions or just 4 Gy in 2 fractions. The original results showed that 4 Gy in 2 fractions was not non-inferior with a median time to progression of 11.7 versus 19.3 months. Longer follow-up continues to show that freedom from local progression is significantly lower with 4 Gy than 24 Gy at 2-years (79.8 vs 94.1%) and 5-years (70.4 vs 89.9%). Over that time the absolute difference in freedom from progression between arms grew from 14.3→ 19.5%. Among the subgroup of patients treated with curative intent (~40%), that difference appeared even larger with 22% of patients in the 4 Gy arm having local progression compared to 4% with 24 Gy. Toxicity was expectedly low in both arms. So, 24 Gy is clearly the superior choice when treating indolent lymphoma with a goal of long-term control. However, the efficacy of just 4 Gy in 2 fractions is not to be ignored when treating patients with palliative intent. In fact, there is no difference in survival between arms, and 4 Gy in 2 fractions doesn’t preclude additional radiation to that site.

TBL: 24 Gy remains superior to 4 Gy when treating follicular and marginal zone lymphoma with a nearly 20% absolute improvement in freedom from local progression at 5 years. | Hoskin, Lancet Oncol 2021

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