Table 1. Characteristics of 14 Cohorts from 11 Included Studies.
| Authors (Publication Year) | Nation | Multicenter | Study Design | Recruitment Period | Response Criteria | Response Assessment Time after Initiation of Therapy (Weeks) | ICI Used | Radiotherapy | Symptoms | Analysis | Treated No. |
|---|---|---|---|---|---|---|---|---|---|---|---|
| ICI monotherapy | |||||||||||
| Weber et al. (2011) (38) | USA | Yes | Retrospective | NR | mWHO | 12 | Ipilimumab | - | NR | Per-patient | 12 |
| Margolin et al. (2012) (26) | USA | Yes | Phase II trial | 2008.7–2009.6 | mWHO, irRC | 12 | Ipilimumab | - | Asymptomatic | Per-patient | 51 |
| Margolin et al. (2012) (26) | USA | Yes | Phase II trial | 2008.7–2009.6 | mWHO, irRC | 12 | Ipilimumab | - | Symptomatic | Per-patient | 21 |
| Queirolo et al. (2014) (37) | Italy | Yes | Retrospective | NR | irRC | 12 | Ipilimumab | - | Asymptomatic | Per-patient | 145 |
| Long et al. (2018) (15) | Australia | Yes | Phase II trial | 2014.11–2017.4 | mRECIST 1.1† | 4 | Nivolumab | - | Mixed | Per-patient | 41 |
| Kluger et al. (2019) (36) | USA | No | Phase II trial | 2014.3–2015.8 | mRECIST 1.1* | 8 | Pembrolizumab | - | Asymptomatic | ||
| ICI combined with radiotherapy | |||||||||||
| Silk et al. (2013) (21) | USA | No | Retrospective | 2005–2012 | irRC | 4–16 | Ipilimumab | WBRT/SRS | Mixed | Per-patient | 22 |
| Anderson et al. (2017) (18) | USA | No | Retrospective | 2014.1–2015.12 | RANO-BM | 6–8 | Pembrolizumab | SRS | NR | Per-lesion | 23 |
| Anderson et al. (2017) (18) | USA | No | Retrospective | 2014.1–2015.12 | RANO-BM | 6–8 | Ipilimumab | SRS | NR | Per-lesion | 31 |
| Nardin et al. (2018) (19) | France | No | Retrospective | 2012–2015 | RECIST 1.1 | 4 | Pembrolizumab | SRS | Mixed | Per-patient | 25 |
| Trommer-Nestler et al. (2018) (20) | Germany | No | Retrospective | 2011.8–2016.9 | RANO-BM | 12 | Pembrolizumab/nivolumab | SRS | NR | Per-lesion | 28 |
| ICI combination therapy | |||||||||||
| Long et al. (2018) (15) | Australia | Yes | Phase II trial | 2014.11–2017.4 | mRECIST 1.1* | 4 | Nivolumab + ipilimumab | - | Asymptomatic | Per-patient | 35 |
| Tawbi et al. (2018) (16) | USA | Yes | Phase II trial | 2015.2–2017.6 | mRECIST 1.1‡ | 4 | Nivolumab + ipilimumab | - | Asymptomatic | Per-patient | 94 |
| Tawbi et al. (2019) (17) | USA | Yes | Phase II trial | NR | mRECIST 1.1‡ | 4 | Nivolumab + ipilimumab | - | Symptomatic | Per-patient | 18 |
*Up to five target lesions of 5 mm or greater or at least twice the slice thickness if 2.5 mm or greater, †Up to five target lesions of 5–40 mm in diameter, ‡Up to five target lesions of 5–30 mm in diameter including target lesions measuring 5 to 10 mm in their longest diameter. ICI = immune checkpoint inhibitor, irRC = immune-related Response Criteria, mRECIST = modified RECIST, mWHO = modified World Health Organization, NR = not reported, RANO-BM = Response Assessment in Neuro-Oncology brain metastases, RECIST = Response Evaluation Criteria in Solid Tumors, SRS = stereotactic radiosurgery, WBRT = whole brain radiation therapy