Case Report: Simultaneous stereotactic re-irradiation using HyperArc for 44 brain metastases after whole-brain...

Treatment options for disseminated intracranial recurrence after whole-brain radiotherapy (WBRT) are limited. Repeat WBRT offers modest efficacy and may worsen neurocognitive function. Modern single-isocenter techniques such as HyperArc may enable efficient stereotactic radiotherapy (SRT) of numerous brain metastases.

A 62-year-old man with extensive-stage small-cell lung cancer and more than 40 brain metastases received systemic therapy followed by WBRT with 30 Gy in 10 fractions, resulting in near-complete intracranial regression. Approximately ten months later, magnetic resonance imaging revealed 41 new lesions and progression of 3 previously detected metastases. Because of his excellent performance status, all 44 lesions were treated with fractionated HyperArc SRT using 21.0 Gy in 3 fractions. Standardized neurocognitive testing was performed before SRT and repeated after 4 and 12 weeks. It demonstrated only selective deterioration without global or subjectively relevant impairment. Follow-up imaging after subsequent initiation of tarlatamab showed marked regression after 4 weeks and near-complete response after 3 months. Two additional lesions were subsequently treated with SRT, followed 7 months later by a second HyperArc course for 8 new metastases. At last follow-up, no treated lesion had locally recurred, and no radiographic radionecrosis was observed.

Fractionated single-isocenter HyperArc SRT may represent a feasible salvage option for carefully selected patients with extensive intracranial recurrence after WBRT. The observed local control and limited neurocognitive deterioration support further prospective evaluation of this approach.