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Focus on HER3 in breast cancer
Slide Deck
View the HER3 slide deck
How common is HER3 in breast cancer?
HER3 has been measured in several breast cancer studies, with varying results.
| Source | N | Definition of HER3 overexpression/HER3
amplification | Percentage of tumors with HER3 overexpression/HER3 amplification |
|---|---|---|---|
| Fuchs et al, Anticancer Res, 20068 | 48 | Immunoreactivity score (IRS) >3 by FISH for cytoplasm and membrane staining combined | 25% in primary tumors 29% in metastases |
| Witton et al, J Pathol, 20033 | 220 | 3+ staining by IHC | 17.5% |
| Naidu et al, Br J Cancer, 199812 | 104 | Strong staining by IHC | 54% of primary breast carcinomas |
| Travis et al, Br J Cancer, 199613 | 491 | Strong staining by IHC | 15% of operable breast cancers 35% of advanced breast cancers |
| Gasparini et al, Eur J Cancer, 199414 | 212 | “Strong and generalised positivity” by IHC | 13% |
- The variability in results suggests a need for a more consistent method of HER3 testing15
- HER3 is frequently co-expressed with HER2 in breast cancer, as shown in human tumor cell lines, mouse transgenic tumors, and human primary breast cancers16
Is HER3 related to other breast cancer tumor markers?
The relationship between HER3 and other breast cancer tumor markers is still under investigation. However, one study suggests that HER3 and the progesterone receptor (PR) may have an inverse relationship.
- In a 2005 study of 402 ER-positive patients treated with tamoxifen, there was a statistically significant inverse relationship between expression of HER3 and expression of PR (P=0.001)10
- The clinical significance of this finding is unknown
