Indications Newly diagnosed adult solid brain metastases with a maximum diameter of less than 3 cm and a mild occupying effect (midline shift of less than 1 cm) [8]. 1, Comparison of stereotactic radiosurgery + whole brain external radiotherapy with whole brain external radiotherapy alone showed that (i) for patients with single brain metastases and KPS ≥ 70 score, single stereotactic radiosurgery + whole brain external radiotherapy was able to significantly prolong patient survival (grade 1) compared with whole brain external radiotherapy alone; (ii) for patients with one to four brain metastases and KPS ≥ 70 score, single stereotactic radiosurgery + whole brain external radiotherapy was superior to whole brain radiotherapy in terms of local control of tumor and maintenance of patient’s functional status (Grade 1); (3) for patients with 2-3 brain metastases, single stereotactic radiosurgery + whole brain radiotherapy significantly prolonged patient survival compared with whole brain radiotherapy alone (Grade 2); (4) for patients with single or multiple brain metastases and KPS <70, single stereotactic radiosurgery + whole brain radiotherapy significantly improved patient survival (Grade 2). whole-brain external radiotherapy was superior to whole-brain external radiotherapy alone in improving patient survival (grade 3) [8-9]. 2, Stereotactic radiosurgery + whole brain external radiotherapy is comparable to stereotactic radiosurgery alone in improving patient survival (level 2), but there is Class I evidence that stereotactic radiosurgery + whole brain external radiotherapy reduces distant recurrence; therefore, the Guidelines recommend regular monitoring of patients treated with stereotactic radiosurgery only to enable early detection of local and distant lesion recurrence and to provide remedial treatment as soon as possible [8]. remedial treatment as soon as possible [8]. Both surgical resection + whole-brain external radiotherapy and stereotactic radiosurgery ± whole-brain external radiotherapy are effective treatment strategies, and patients treated with both regimens have similar survival; however, there is no evidence-based treatment effect of stereotactic radiosurgery for lesions that are large (>3 cm) or have significant occupational effects (midline shift >1 cm) (level 2) [8]. 4, Stereotactic radiosurgery alone and whole brain external radiotherapy alone are both effective strategies for the treatment of brain metastases, but stereotactic radiosurgery alone is superior to whole brain external radiotherapy in terms of prolonged survival in patients with less than 3 metastases (grade 3) [8]. 5, domestic experience Based on the summary of 780 cases of brain metastases treated with gamma knife, it is proposed that: ① the average tumor diameter <3 cm and the maximum diameter ≤4 cm is appropriate; ② the vast majority of patients can be treated at one time, and it is appropriate to treat up to 4 lesions at one time; ③ for metastases less than 2 cm in diameter, 6-8 lesions can be treated at one time; ④ patients with more metastases and larger tumor volume can be treated in ⑤ Those with intracranial hypertension before treatment cannot be completely regarded as contraindications and can be treated with mannitol and hormones at the same time. Shen Guangjian et al [11] concluded that radiosurgery is more effective in brain metastases that respond well to combined use of dexamethasone and mannitol, and suggested it as a crude but practical criterion for selecting cases and judging prognosis, especially for those for whom pathological diagnosis is not available.