Table 2.
Included clinical study characteristics
| Characteristic | Number of studies |
|---|---|
| Total | 87 |
| Publication type | |
| Full journal article | 71 |
| Abstract | 13 |
| Clinicaltrials.gov record | 3 |
| Study type | |
| Clinical trial | 12 |
| Observational (retrospective) | 66 |
| Observational (prospective) | 6 |
| Observational (prospective-retrospective) | 3 |
| Year of data collection end | |
| Pre-2015 | 0 |
| 2015–16 | 4 |
| 2017–18 | 32 |
| 2019–20 | 36 |
| 2021–current | 12 |
| NR | 3 |
| Region of investigation | |
| Europe | 14 |
| North America | 36 |
| South America | 3 |
| Asia | 23 |
| International | 6 |
| NR | 5 |
| Breast cancer subtype | |
| Early BC | 0 |
| Metastatic BC | 87 |
| HR+/HER2−a | 83 |
| HR+/HER2+a | 1 |
| HR−/HER2+ | 0 |
| HR−/HER2− | 0 |
| ER+ (HER2 status not specified) | 1 |
| NR (metastatic but subgroup not specified) | 2 |
| Metastatic breast cancer typeb | |
| De novo | 20 |
| Recurrent | 11 |
| Distant metastases | 3 |
| NR | 70 |
| Number of metastatic sitesb | |
| < 3 | 18 |
| ≥ 3 | 19 |
| NR | 69 |
| Visceral/bone diseaseb | |
| Visceral disease | 45 |
| Bone/bone marrow only | 43 |
| NR | 34 |
| CDK4/6i line of therapy | |
| 1L only | 1 |
| 2L only | 5 |
| 3L+ only | 0 |
| Multiple linesc | 73 |
| 1L+ | 62 |
| 2L+ | 11 |
| 3L+ | 0 |
| NR/reported post-CDK4/6i only | 8 |
| Post-CDK4/6i therapy evaluatedb | |
| ET only | 26 |
| CT only | 24 |
| mTORi-based only | 12 |
| CDK4/6i-based only | 16 |
| Combination of mTORi- and CDK4/6i-based therapies | 1 |
| Regimen unspecifiedd | 11 |
| NR | 41 |
# number of lines of therapy, 1L first line, 2L second line, 3L third line, CDK4/6i cyclin-dependent kinase 4/6 inhibitor, CT chemotherapy, ER estrogen receptor, ET endocrine therapy, HER2 human epidermal growth factor receptor 2, HR hormone receptor, mBC metastatic breast cancer, mTORi mammalian target of rapamycin inhibitor, NR not reported
aHR+ includes studies reported as ER+ only
bStudies that reported characteristic for multiple categories were counted in each category
cStudies were grouped into the most appropriate category; groups are mutually exclusive. For example, a study reported CDK4/6i in 1L, 2L, and 3L+ settings would be counted as 1L+
dIncluding targeted therapy, best supportive care, and investigational drugs