Table 1. General characteristics of included articles.
| HER2-zero | HER2-low | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Study | Type of study | Country | Types of cancer included | Antibody used | Scoring system | Number of individuals | Mean age | IHC 0 | IHC 1+ | IHC2+ ISH- | HER2-zero prevalence (%) | HER2-low prevalence (%) | |
| Pinheiro et al. 2024 (18) | Cohort | Brazil | I-III | NA | ASCO/CAP guidelines (2018) | 512 | 51 | 230 | 226 | 56 | 44.9 | 55.1 | |
| Peiffer et al. 2023 (19) | Cohort | US/ Hispanics | Invasive | NA | NA | 62,985 | 62.4 | 24,536 | 27,978 | 10,471 | 39.0 | 61.0 | |
| Fernandes et al. 2023 (20) | Cross-sectional | Brazil | Invasive stages I-III | NA | ASCO/CAP guidelines (2018) | 179 | 55 | 128 | 51 | 71.5 | 28.5 | ||
| Martinez-Cannon et al. 2023 (21) | Cohort | Mexico | Metastatic | NA | NA | 44 | 51 | 18 | 26 | 40.9 | 59.1 | ||
| Vargas et al. 2023 (22) | Cohort | Colombia | stages I-III | NA | NA | 422 | NA | 325 | 97 | 77.0 | 23.0 | ||
| López-Altamirano et al. 2023 (23) | Cross-sectional | Mexico | All | NA | ASCO/CAP guidelines (2007) | 159 | 48,1 | 119 | 40 | 74.8 | 25.2 | ||
| Jiang et al. 2022 (24) | Cohort | US/ Hispanics | Metastatic | NA | ASCO/CAP guidelines (2018) | 1682 | NA | 646 | 1036 | 38.4 | 61.6 | ||
| Reinert et al. 2021 (25) | Cohort | Brazil | All | NA | NA | 331 | NA | 164 | 167 | 49.5 | 50.4 | ||
| Moura Leite et al. 2021 (26) | Cohort | Brazil | All | NA | ASCO/CAP guidelines (2007) | 855 | 45 | 570 | 181 | 104 | 66.7 | 33.3 | |
| Arias et al. 2017 (27) | Cross-sectional | Brazil | Invasive | Anti-HER-2 antibody PATHWAY ® (4B5) | ASCO/CAP guidelines (2007) | 1,029 | 55,4 | 627 | 313 | 89 | 60.9 | 39.1 | |
| Plata et al. 2013 (28) | Cross-sectional | Colombia | Invasive | Herceptest methodology (Dako K5204) | ASCO/CAP guidelines (2007) | 2,709 | NA | 1145 | 613 | 951 | 42.3 | 57.7 | |
| Wludarski et al 2011 (29) | Cross-sectional | Brazil | Invasive | Antibody SP3 (code RM-9103-S, NeoMarkers, Lab Vision Corp, Fremont, CA) | ASCO/CAP guidelines (2007) | 651 | NA | 209 | 148 | 294 | 32.1 | 67.9 | |
NA, not available. ASCO/CAP, American Society of Clinical Oncology / College of American Pathologists. IHC, immunohistochemistry. ISH, in situ hybridization