标准的全脑放射治疗（WBRT）对于小细胞肺癌（SCLC）所致的大脑转移灶（BMs）的疗效和持久性有限，而单独进行立体定向放射手术（SRS）治疗症状性后颅窝大于3 cm且具有卫星病灶的BM是具有挑战性的。在本文中，我们报告了一例73岁的女性患者，首次出现未经治疗的SCLC并伴有15个症状性多个BM，其中包括一个直径≥3.8 cm（体积≥17.7 cm3）的小脑肿瘤和两个相邻病灶；除此以外，SCLC限于胸廓内。患者最初接受常规WBRT（10次30 Gy）和卡铂、依托泊苷和阿特伯珠单抗联合化疗免疫治疗（CIT）。辐照期间不使用阿特伯珠单抗。WBRT后的5个月，大脑小脑肿瘤明显缩小，较小的病灶（≤17 mm）在20个月时显示完全缓解而无局部进展。然而，WBRT后的6个月和16个月，胸部病灶进展，尽管使用了阿莫霉素治疗，但分别发展出包括脑桥受累在内的四个新的脑转移灶。尽管经历了SRS（8次49.6 Gy）后四个脑转移灶的完全缓解以及胸部病灶的持续缩小，患者在SRS后3.5个月出现脑膜播散和多个新的脑转移灶。大转移灶的小残留部分和/或与脑脊液相邻的新发生的脑转移灶可能导致脑脊液播散，这是导致患者死亡的推测性原因。总体而言，联合化疗-WBRT和随后的CIT可以为SCLC的BM提供出色和持久的肿瘤缓解，但对于≥3.8 cm的BM可能还不足够。因此，在大病灶的情况下，可以考虑对大病灶进行局部剂量递增，联合胸部放射治疗，并在巨观未受累脑区进行剂量递减，以预防或减轻脑脊液播散、新的BM发生和不良反应。版权所有 © 2023年，Ohtakara等人。

Standard whole-brain radiotherapy (WBRT) alone for large brain metastases (BMs) from small cell lung cancer (SCLC) has limited efficacy and durability, and stereotactic radiosurgery (SRS) alone for symptomatic posterior fossa BMs >3 cm with satellite lesions is challenging. Herein, we describe the case of a 73-year-old female presenting with treatment-naïve SCLC and 15 symptomatic multiple BMs, including a ≥3.8-cm cerebellar mass (≥17.7 cm3) and two adjacent lesions; otherwise, the SCLC was confined to the thorax. The patient was initially treated concurrently with conventional WBRT (30 Gy in 10 fractions) without boost and chemoimmunotherapy (CIT) consisting of carboplatin, etoposide, and atezolizumab. Atezolizumab was excluded during irradiation. Five months after WBRT, the large cerebellar lesion had remarkably regressed, and the smaller lesions (≤17 mm) showed complete responses (CRs) without local progression at 20 months. However, six and 16 months after WBRT, the thoracic lesions had progressed, and although amrubicin was administered, four new BMs, including pons involvement, had developed, respectively. Despite the CRs of the four BMs following SRS (49.6 Gy in eight fractions) and the sustained regression of the thoracic lesions, meningeal dissemination and multiple new BMs were evident 3.5 months post-SRS. The small remnant of the large BM and/or newly developed BMs abutting the cerebrospinal fluid (CSF) space could have led to CSF dissemination, the presumed cause of the patient's death. Taken together, concurrent chemo-WBRT and subsequent CIT can provide excellent and durable tumor responses for SCLC BMs, but may not be fully sufficient for BMs ≥3.8 cm. Therefore, in cases with large lesions, focal dose escalation of the large lesions, consolidative thoracic radiotherapy, and dose de-escalation in the macroscopically unaffected brain region may prevent or attenuate CSF dissemination, new BM development, and adverse effects and thus should be considered.Copyright © 2023, Ohtakara et al.