Table 2.

Attrition table for real-world chemotherapy cohort

	N
All MBC in Flatirona Health real-world cohort (Feb 2018)	15,277
Include all female patients with MBC diagnosed from 1 Jan, 2011–28 Feb, 2018	15,073
Include patients who had any single-agent treatment of (capecitabine, gemcitabine, eribulin, or vinorelbine) in line 2 or later	2312
Exclude any patient with prior trastuzumab, pertuzumab, lapatinib, or ado-trastuzumab emtansine treatment	2145
Select patients with eligible linesb (capecitabine, gemcitabine, eribulin, and vinorelbine) without ECOG missing	281

CDK Cyclin-dependent kinase, CNS central nervous system, ECOG PS eastern cooperative oncology group performance status, EHR electronic health record, ER estrogen receptor, HER2 human epidermal growth factor receptor 2, MBC metastatic breast cancer, N total number of patients, PR progesterone receptor

^aFlatiron Health EHR database (https://flatiron.com/real-world-evidence/) 02 2018^*

^bEligible line contains any single-agent treatment (capecitabine, gemcitabine, eribulin, and vinorelbine) (a) received 1–2 lines of therapy containing chemotherapy drug prior to eligible line, (b) had a positive test for ER or positive test for PR on or before the eligible line, (c) had a negative test for HER2 on or before the line containing single-agent treatment, (d) had an ECOG PS ≤ 1 (60 day window prior or 30 days after), (e) no diagnosis codes for CNS metastasis on or before the eligible line, (f) eligible line occurs ≥ 3 months prior to end of database, (g) no CDK4 & 6 inhibitor and no clinical study drug prior to the eligible line

^*Date of most recent dataset utilized in the analyses, Feb 2018, mortality v2.0