2. HER2 RECEPTOR
HER2 is part of the epidermal growth factor family, along with 3 other receptors with no identifiable ligand
The HER2 gene is located on the long arm of chromosome 17 and encodes a 185-kDa transmembrane protein
It is present in an active conformation and can undergo ligand-independent dimerization with other EGF
receptors
HER2 overexpression is present in approximately 2030% of breast cancer tumors.
3. Gutierrez C, Schiff R. HER2: biology, detection, and clinical implications. Arch Pathol Lab Med. 2011
4. American Society of Clinical Oncology/College of American Pathologists Guideline Recommendations for Human Epidermal Growth Factor Receptor 2 Testing in Breast Cancer
5. HER 3 RECEPTOR
HER3 is a member of the HER family, which is composed of four homologous receptors tyrosine kinases
The neuregulin also called the heregulin is the unique ligand of HER3 that activate HER3-ECD
HER3 mostly heterodimerizes with HER2, and the HER2-HER3 heterodimer is the most active signaling dimer in this family
HER3 is a potent activator for PI3K/AKT and other signaling pathways such as MEK/MAPK, PLC粒/PKC, Jak/Stat, and Src
kinase, which have a crucial role in cellular growth, proliferation, and survival
HER3 protein is overexpressed in about 5070 % of breast cancers with the HR+/HER2- subtype showing the highest
expression (followed in order by HR+/HER2+ and HR-/HER2+ subtypes
HER3 expression also plays a key role in developing metastases in specific organs, such as bone and brain
HER3 upregulation is associated with acquired resistance to chemotherapy, endocrine therapy, and HER2- and
PI3K/AKT/mTOR targeting therapy
6. TRANSTUZUMAB
Trastuzumab, a humanized IgG1 monoclonal antibody that targets the extracellular domain of the HER2 protein
It targets subdomain IV of the HER2 extracellular domain, exerting its antitumor effect by blocking HER2 cleavage, downstream
proliferation pathways, and promoting apoptosis.
Additionally, it stimulates endocytosis and prevents shedding of the extracellular domain of HER2.
It also triggers antibody-dependent cellular cytotoxicity
The most concerning adverse effect is cardiotoxicity which is increased when trastuzumab is combined with anthracyclines.
Early studies demonstrated that New York Heart Association (NYHA) class III or IV heart failure occurred in up to 27% of
patients treated with anthracycline, cyclophosphamide, and trastuzumab.
Evaluation of left ventricular ejection fraction (LVEF) is recommended prior to initiation of adjuvant trastuzumab, every 3
months while on treatment, at completion, and every 6 months for 2 years after treatment is completed.
Most cardiac toxicity is reversible with vigilant monitoring and early cessation of trastuzumab when it occurs
8. NSABP-B-31 and NCCTG-N9831 Study Arms
= doxorubicin/cyclophosphamide (AC) 60/600 mg/m2
q3wk x 4
= paclitaxel (P) 175 mg/m2
q3wk x 4
= paclitaxel (P) 80 mg/m2
qwk x 12
= trastuzumab (H) 4 mg/kg LD + 2 mg/kg qwk x 51
NSABP-B-31
NCCTG-N9831
Arm 1
Arm 2
Arm C
Arm A
Arm B
9. N9831/B-31 Disease-Free Survival
DFS
AC P + H
(n = 2,028)
AC P
(n =
2,018)
10-year DFS* 73.7% 62.2%
First DFS events
Distant recurrence
Local/regional recurrence
Contralateral breast cancer
Other second primary cancer
Death without recurrence
11.2%
4.1%
2.3%
3.3%
1.9%
19.4%
6.1%
2.0%
3.7%
1.5%
* Adjusted HR = 0.6, p < 0.0001
10. N9831/B-31 Overall Survival
OS
AC P+H
(n = 2,028)
AC P
(n = 2,018)
10-year OS* 84.0% 75.2%
OS events
Deaths
Due to this breast cancer
Due to second primary cancer
Due to other causes
Cause unknown
14.1%
10.3%
1.2%
0.9%
1.6%
20.7%
16.8%
2.0%
0.7%
1.1%
* Adjusted HR = 0.63, p < 0.0001
17. The combination of trastuzumab with anthracycline increases the risk of congestive heart failure by a factor of 4 to 5
and approximately 10% of patients treated with trastuzumab have a substantial decrease in their LVEF
18. 10-year DFS was 74.6% with AC-DH (p < 0.0001), 73.0% with TCH (p= 0.0011), and 67.9% with AC-D.
Overall survival at 10 years was 85.9% with AC-DH, 83.3% with TCH and 78.7% with AC-D, representing risk
reductions of 27% (p < 0.0001) and 24% (p = 0.0075), respectively.
19. TCH is an acceptable adjuvant regimen that may lessen the risk of cardiotoxicity
21. Trastuzumab emtansine (T-DM1), an antibodydrug conjugate
of trastuzumab and the cytotoxic agent emtansine (DM1), a
maytansine derivative and microtubule inhibitor, provides
benefit in patients with metastatic breast cancer that was
previously treated with chemotherapy plus HER2-targeted
therapy.
25. The 6-year OS difference remains insignificant with 95% in the pertuzumab group compared to 94% in the placebo
group
Toxicity was increased with dual HER2-blockade particularly in the form of diarrhea with a 9.8% rate of grade 3 or
higher diarrhea in the pertuzumab group compared to 3.7% in the placebo group.
The risk of diarrhea was even greater among patients treated with the docetaxel and carboplatin regimen at 18%.
Cardiac toxicity was similar between treatment arms.
27. Neratinib significantly improved iDFS in
the HER2+
/HR+
/ 1-year population, and
a similar trend was observed in patients
with residual disease following
neoadjuvant treatment.
Numerical improvements in central
nervous system events and OS were
consistent with iDFS benefits and suggest
long-term benefit for neratinib in this
population.
Diarrhoea was the important side effect.