KEY POINTS
- The report describes a 62-year-old patient with extensive-stage SCLC who initially presented with more than 40 brain metastases and received WBRT to 30 Gy in 10 fractions, achieving near-complete intracranial regression.
- Approximately 10 months later, MRI demonstrated 41 new metastases plus progression of 3 known lesions, for a total of 44 targets. Lesions were small, with maximum diameter 8 mm, there was no leptomeningeal disease, and performance status remained excellent at KPS 90.
- Rather than repeat WBRT, all 44 lesions were treated simultaneously with single-isocenter HyperArc stereotactic RT to 21 Gy in 3 fractions. Total GTV was only 4.15 cm³ and total PTV 34.91 cm³, highlighting that lesion number alone did not reflect total intracranial tumor burden.
- Treatment remained operationally efficient despite the lesion count: median treatment time was 13.5 minutes per fraction, with only 3.5 minutes of beam-on time. Overall GTV coverage was 97.6%; coverage was intentionally compromised for lesions directly adjacent to the optic pathway.
- Standardized neurocognitive testing showed selective deterioration in visuospatial learning, processing speed and executive function, but no evidence of global cognitive decline or rapid hippocampal-type forgetting. The patient reported no meaningful decline in everyday cognitive function.
- MRI showed marked regression by 4 weeks and near-complete response by 3 months. No treated lesion subsequently showed local recurrence, and no radiographic radionecrosis had developed at last follow-up; however, tarlatamab was started two weeks after SRT, making the radiographic response impossible to attribute to RT alone.
- Intracranial disease continued to emerge outside treated areas: two new metastases were treated separately and, seven months later, another 8 lesions received a second 21 Gy/3-fraction HyperArc course. This remains a single case with limited follow-up for delayed radionecrosis and long-term neurocognition.
CLINICAL TAKEAWAY
This case challenges the idea that lesion count alone should automatically preclude stereotactic salvage after WBRT: 44 small metastases were treated in one efficient HyperArc plan. But it is a technical proof of feasibility, not evidence that treating dozens of recurrent metastases is superior to repeat WBRT or systemic therapy; total tumor volume, lesion geometry, performance status and systemic options remain critical.