Differences in Treatment Outcomes Between Patients with HER2-Low versus HER2-Zero, Hormone Receptor-Positive Advanced-Stage Breast Cancer Treated with Ribociclib

Figures & data

Table 1 Characteristics of the Patients (n = 257)

	HER2-Zero (N=114)	HER2-Low (N=143)	Total (N=257)	p value
Age				0.008^a
Mean (SD)	52.1 (12.1)	48.2 (11.4)	49.9 (11.8)
Range	29.0–87.0	22.0–72.0	22.0–87.0
Histology				0.238^b
Ductal	96 (84.2%)	115 (80.4%)	211 (82.1%)
Lobular	12 (10.5%)	24 (16.8%)	36 (14.0%)
Others	6 (5.3%)	4 (2.8%)	10 (3.9%)
Tumor grade				0.769^b
Grade I	9 (7.9%)	8 (5.6%)	17 (6.6%)
Grade II	61 (53.5%)	85 (59.4%)	146 (56.8%)
Grade III	35 (30.7%)	40 (28.0%)	75 (29.2%)
Unknown	9 (7.9%)	10 (7.0%)	19 (7.4%)
Timing of metastasis				0.287^b
De novo	65 (57.0%)	72 (50.3%)	137 (53.3%)
Recurrent	49 (43.0%)	71 (49.7%)	120 (46.7%)
Site of metastasis				0.084^b
Non-visceral	61 (53.5%)	61 (42.7%)	122 (47.5%)
Visceral	53 (46.5%)	82 (57.3%)	135 (52.5%)
Menopausal status^b				0.111^b
Premenopausal	48 (42.1%)	74 (52.1%)	122 (47.7%)
Postmenopausal	66 (57.9%)	68 (47.9%)	134 (52.3%)
Smoking				0.918^b
Non smoker	80 (70.2%)	102 (71.3%)	182 (70.8%)
Smoker	16 (14.0%)	21 (14.7%)	37 (14.4%)
Unknown	18 (15.8%)	20 (14%)	38 (14.8%)
Lines of treatment				0.110^b
First line	78 (68.4%)	84 (58.7%)	162 (63.0%)
Second line and beyond	36 (31.6%)	59 (41.3%)	95 (37.0%)
Prior Chemotherapy				0.047
No	85 (74.6%)	90 (62.9%)	175 (68.1%)
Yes	29 (25.4%)	53 (37.1%)	82 (31.9%)

Note: ^aLinear Model ANOVA. ^bPearson’s Chi-squared test.

Figure 1 Progression-free survival for HER2-low versus HER2-zero.

Note: Progression-free survival was higher for HER2-zero.

Table 2 Univariable and Multivariable Cox Proportional Regression Analysis of Variable with Progression-Free Survival

Variable		PFS (Univariable)	PFS (Multivariable)
		HR (95% CI, p-value)	HR (95% CI, p-value)
Age^a		1.00 (0.99–1.02, p=0.776)
Histology	Ductal	1 [Reference]
	Lobular	0.77 (0.46–1.28, p=0.306)
	Others	0.49 (0.16–1.54, p=0.221)
Tumor grade	Grade I	1 [Reference]
	Grade II	1.16 (0.56–2.41, p=0.684)
	Grade III	1.64 (0.77–3.48, p=0.201)
	Unknown	1.09 (0.43–2.76, p=0.855)
Timing of metastasis	De novo	1 [Reference]
	Relapsed	1.35 (0.97–1.89, p=0.076)
Site of metastasis	Non-visceral	1 [Reference]	1 [Reference]
	Visceral	1.81 (1.29–2.54, p=0.001)	1.57 (1.10–2.24, p=0.013)
Menopausal status	Premenopausal	1 [Reference]
	Postmenopausal	1.25 (0.90–1.75, p=0.187)
Smoking	Non smoker	1 [Reference]
	Smoker	0.85 (0.51–1.43, p=0.550)
	Unknown	0.86 (0.54–1.36, p=0.509)
Prior Chemotherapy	No	1 [Reference]	1 [Reference]
	Yes	1.80 (1.27–2.55, p=0.001)	0.74 (0.42–1.29, p=0.284)
HER2	Zero	1 [Reference]	1 [Reference]
	Low	1.67 (1.19–2.36, p=0.003)	1.51 (1.06–2.13, p=0.021)
Lines of treatment	First line	1 [Reference]	1 [Reference]
	Second line and beyond	2.25 (1.60–3.16, p<0.001)	2.47 (1.44–4.22, p=0.001)

Note: ^aMean (SD) 49.9 (11.8).