Top Line: How hot can you treat brainstem metastases without getting burned?
The Study: Treating brainstem metastases with SRS is a challenge. On the one hand, the brainstem is important real estate, so we often want to be conservative to avoid severe toxicity. On the other hand, being too conservative could lead to a local recurrence that could still lead to severe consequences or require reirradiation. This large pooled analysis included 2237 patients and 2432 brainstem lesions across 28 studies plus the authors’ institutional cohort. The most frequently used regimens were 16 Gy in 1 fraction and 24 Gy in 3 fractions. They modelled tumor control probability after SRS or fractionated SRS using a linear-quadratic framework. Fitting three radiobiologic models yielded a surprisingly consistent α/β ≈20 Gy, which is in line with prior HyTEC brain metastasis data. A BED20 of ~36.8 Gy predicted 90% 1-year TCP, while ~41.4 Gy predicted 90% 2-year TCP. The latter corresponds to 20.5 Gy in 1 fraction, 28.2 Gy in 3 fractions, or 31.5 Gy in 5 fractions. Smaller lesions (<0.4 cc) enjoyed higher TCP at similar doses. Before your contouring hand starts to tremble, grade ≥3 adverse events (including radionecrosis) were relatively low (3.1%), with a single grade 5 hemorrhage (0.04%).
TBL: This study challenges some of our assumptions about SRS dose in the brainstem. While median prescription doses were below those typically used outside the brainstem, the rate of grade 3+ adverse events was relatively low. For carefully selected patients, standard SRS doses may provide long term control with acceptable risk of adverse events. | Xu, Radiother Oncol 2026
The Study: Treating brainstem metastases with SRS is a challenge. On the one hand, the brainstem is important real estate, so we often want to be conservative to avoid severe toxicity. On the other hand, being too conservative could lead to a local recurrence that could still lead to severe consequences or require reirradiation. This large pooled analysis included 2237 patients and 2432 brainstem lesions across 28 studies plus the authors’ institutional cohort. The most frequently used regimens were 16 Gy in 1 fraction and 24 Gy in 3 fractions. They modelled tumor control probability after SRS or fractionated SRS using a linear-quadratic framework. Fitting three radiobiologic models yielded a surprisingly consistent α/β ≈20 Gy, which is in line with prior HyTEC brain metastasis data. A BED20 of ~36.8 Gy predicted 90% 1-year TCP, while ~41.4 Gy predicted 90% 2-year TCP. The latter corresponds to 20.5 Gy in 1 fraction, 28.2 Gy in 3 fractions, or 31.5 Gy in 5 fractions. Smaller lesions (<0.4 cc) enjoyed higher TCP at similar doses. Before your contouring hand starts to tremble, grade ≥3 adverse events (including radionecrosis) were relatively low (3.1%), with a single grade 5 hemorrhage (0.04%).
TBL: This study challenges some of our assumptions about SRS dose in the brainstem. While median prescription doses were below those typically used outside the brainstem, the rate of grade 3+ adverse events was relatively low. For carefully selected patients, standard SRS doses may provide long term control with acceptable risk of adverse events. | Xu, Radiother Oncol 2026