Abstract 23P
Background
HER2 low was considered a heterogeneous group of tumors, primarily by the presence or absence of hormone receptor (HR) expression. We sought to describe the clinicopathological features of HER2 low tumors in a real-world setting in China while controlling for HR positive.
Methods
Patients diagnosed with HR+ early breast cancer (eBC) were identified from a prospective real-world study conducted at 26 county-level hospitals in China. The HER2 status was classified by IHC/FISH analysis as HER2 0, HER2 low (IHC 1+ or 2+ with FISH-), and HER2+ (IHC 3+ or FISH+). Univariable (UVA) and multivariable multinomial logistic regression analysis (MVA) were performed to determine associations among variables and subtypes.
Results
1854 patients were included. 888 (47.9%) were HER2 low, 432 (23.3%) were HER2 0 and 534 (28.8%) were HER2+. Clinicopathologic features are presented in the table. On UVA, compared to HER2 0 tumors, premenopause (OR 1.28 [95% CI 1.01-1.61]; p=.039) and higher rates of Ki67 ≥20% (OR 1.43 [95% CI 1.13-1.81]; p=.003) were associated with HER2 low and clinical stage II-III (OR 1.47 [95% CI 1.07-2.02]; p=.017), histologic grade III (OR 2.40 [95% CI 1.35-4.29]; p=.003), and Ki67 ≥20% (OR 5.20 [95% CI 3.84-7.09]; p<.001) were found to be associated with HER2+. On MVA, compared to HER2 0, HER2 low was associated with Ki67 ≥20% (OR1.47 [95% CI, 1.07-2.02], p=.018). HER2+ was associated with younger age (OR 1.03 [95% CI 1.01-1.06]; p=.017), postmenopause (OR 1.2 [95% CI 1.06-1.36], and Ki67 ≥20% (OR 4.82 [95% CI 3.20-7.37]; p<.001). Table: 23P
| Characteristic n (%) | HER2 0 | HER2 low | HER2+ |
| Median age (IQR) | 52.0 (46.0, 60.0) | 51.0 (46.0, 58.0) | 52.0 (46.0, 58.0) |
| Clinical stage | |||
| I | 112 (37) | 235 (35) | 114 (28) |
| II-III | 193 (63) | 436 (65) | 289 (72) |
| Tumor size | |||
| ≤2cm | 183 (44.5) | 362 (42.7) | 202 (39.5) |
| 2-5cm | 191 (46.5) | 426 (50.2) | 259 (50.7) |
| >5cm | 37 (9.0) | 60 (7.1) | 50 (9.8) |
| Nodal stage | |||
| N0 | 213 (50.8) | 435 (50.1) | 263 (50.6) |
| N1 | 127 (30.3) | 262 (30.1) | 186 (35.8) |
| N2-3 | 79 (18.9) | 172 (19.8) | 71 (13.7) |
| Histologic grade | |||
| I | 30 (8.3) | 72 (9.2) | 28 (6.0) |
| II | 246 (68.0) | 507 (64.9) | 245 (52.6) |
| III | 86 (23.8) | 202 (25.9) | 193 (41.4) |
| Lymph vascular invasion | 89 (20.8) | 182 (20.6) | 118 (22.3) |
| Ki67 ≥20% | 241 (58.2) | 537 (65.5) | 25 (80.6) |
| Premenopausal | 180 (41.8) | 424 (47.8) | 215 (40.4) |
Conclusions
The results showed the clinicopathological features from a large sample of HR+/HER2 low eBC patients in a real-world county setting in China, which serves as a valuable supplement to current researches on HER2 low breast cancer. While controlling for HR positive, it was observed that HER2 low breast cancer features exhibited only marginal differences from HER2 0, suggesting insufficient evidence to support the interpretation of HER2 low as a distinct subtype.
Clinical trial identification
Editorial acknowledgement
Legal entity responsible for the study
The authors.
Funding
AstraZeneca.
Disclosure
All authors have declared no conflicts of interest.