Table 1.

Clinicopathologic characteristics of patients included in study

All patientsDevelopment setValidation set
N1236558
Median age, y60 (30–83)61 (30–83)59 (33–80)
Pathology
 IDC1055649
 ILC1266
 Other330
Histologic grade
 I431
 II502525
 III593029
 Unknown1073
ER-positive864838
HER2-positive20911
HER2 testing site
 Primary543519
 Recurrent693039
Sites metastatic cancer
 Visceral884642
 Nonvisceral351916
Adjuvant chemotherapy3931
Adjuvant tamoxifen3730
No prior metastatic chemo
 03326
 11512
 21112
 355
 413
Prior HER2-directed therapy911

Abbreviations: IDC, invasive ductal carcinoma; ILC, invasive lobular carcinoma; No prior metastatic chemo, number of prior courses of chemotherapy in the metastatic setting.