Impact of HER2+ ratio on efficacy of Trastuzumab in early breast cancer

الملخص EN

Background: Human epidermal growth factor receptor 2 (HER2) is a significant predictive factor for benefit from adjuvant trastuzumab (HER2-targeted therapy) which is considered the standard treatment for patients with HER2+ early breast cancer (EBC) after completion of adjuvant chemotherapy.

We aimed to determine whether the high level of HER2 positivity would influence the outcome of adjuvant trastuzumab and the prognosis at diagnosis.

Patients and methods: 157 Patients with EBC (HER-2 positive, lymph node-positive, hormonal receptors negative) who received adjuvant chemotherapy and trastuzumab (8 mg/kg intravenously as a loading dose followed by 6 mg/kg every 3 weeks for 6 months) at Albairouni University Hospital.

This is a single institute study with two arms based on HER2 positivity ratio.

Group A (HER2 FISH ratio ≤ 4, n =91 patients), and group B (HER2 FISH ratio > 4, n =66 patients).The primary endpoint was 3-years disease free survival (DFS) in relation to HER2 FISH ratio.

Results: The 3-years DFS in the group A was 75.8%, while it was 77.2% in the group B (P = 0.31).

Stage II and III in the group A were 32% and 68% respectively, while for the group B were 27.27% and 72.72% respectively.

Grade (I-II) and (III-IV) for the group A were 60.4% and 39.6% respectively, while for the group B 68.18% and 31.81% respectively.

Differences were not statistically significant.

Conclusion: the High degree of HER2 amplification (FISH ratio >4 vs.

≤4) has no significant influence on either outcome from adjuvant trastuzumab or prognosis in HER2+ EBC.