Table 1 Inclusion and Exclusion Criteria for Level 1 (Titles and Abstracts) and Level 2 (Full-Text) Screening

Study design

▪ Randomized controlled trials

▪ Single-arm studies

▪ Observational research studies (e.g., prospective cohort study, retrospective database study, cohort study, case-control study)

▪ Literature reviews and meta-analyses^a

▪ Natural history studies

▪ Incidence and prevalence studies

▪ Prognostic factor studies

▪ Consensus reports

▪ Preclinical studies

▪ Nonsystematic reviews

▪ Case reports

▪ Case studies/series

▪ Editorials

▪ Commentaries

▪ Letters

▪ Guideline or position statements

▪ Economic analyses

▪ Animal or other nonhuman (e.g., bench) studies

▪ Study of < 25 patients

Population

▪ Patients with diagnosis of metastatic, recurrent, advanced, incurable, or unresectable HER2+ breast cancer (stages 3–4) with BM, either at the time of breast cancer diagnosis or after breast cancer diagnosis

▪ Aged under 18 y

▪ Only patients with HER2− or stage 1 or 2 breast cancer

▪ Only patients with HER2+ breast cancer without BM

Treatment

▪ Evaluation of chemotherapy by mechanism of action

▪ Nonpharmacological studies

▪ Specific regimens of chemotherapy (not mechanism of action)

▪ Patients receiving surgical or radiation intervention in place of chemotherapy

▪ Patients receiving CDK4/6 inhibitors

Evaluation

▪ Incidence or prevalence

▪ Prognostic and/or predictive factors

▪ Treatment outcomes (safety or effectiveness)

▪ PK/PD of treatments