Table 3: Adjusted model for risk of permanent discontinuation of trastuzumab.

CharacteristicAdjusted HR (95% CI)P-Value

Metastases present at trastuzumab initiationBone0.96 (0.72–1.27)0.76
Liver0.93 (0.68–1.27)0.65
Lung/chest0.86 (0.63–1.16)0.32
Other1.02 (0.74–1.40)0.93

Diagnosed with metastases after start of trastuzumab*CNS1.78 (1.11–2.87)0.02
Bone1.17 (0.75–1.84)0.49
Liver1.08 (0.66–1.78)0.76
Lung/Chest0.76 (0.46–1.26)0.29
Other1.58 (0.95–2.64)0.08

Hospital inpatient*No1.00 (ref)0.49
Yes1.34 (0.59–3.06)

Age at start of trastuzumab66–691.00 (ref)
70–741.04 (0.70–1.54)0.86
75–790.95 (0.63–1.44)0.81
≥801.23 (0.81–1.87)0.33

Need line above race/ethnicityWhite1.00 (ref)0.20
Non-White1.24 (0.89–1.72)

Time from MBC diagnosis to trastuzumab initiationPer ln (days)1.00 (0.92–1.09)0.99

NCI comorbidity score at start of trastuzumab01.00 (ref)
10.99 (0.62–1.60)0.98
≥21.68 (0.91–3.08)0.10

Stage at initial diagnosisRecurrent Stage 0–III1.00 (ref)0.005
Incident Stage IV0.65 (0.48–0.88)

ER/PR StatusHormone Positive1.00 (ref)
Hormone Negative1.05 (0.79–1.40)0.73
Unknown1.14 (0.76–1.72)0.53

Note: Asterisk (*) indicates time varying covariate. All listed covariates were included in one model. Nonwhite race includes Black, Hispanic, and Other as a combined category. Baseline defined as the date of trastuzumab initiation. Additional covariates in model that are not shown include a time-varying covariate for new cardiovascular disease and year of trastuzumab initiation (neither of which was statistically significant). Reference group for each metastasis covariate is the absence of the condition (HR = 1.0).