Adjuvant Chemotherapy for HER2-Positive Breast Cancer

Treatment Algorithm Based on Neoadjuvant Response

The National Comprehensive Cancer Network recommends completing 1 year of trastuzumab, starting from the initiation of neoadjuvant therapy, for patients who achieve pathologic complete response (pCR) 1, 2
For patients who received pertuzumab as part of their neoadjuvant regimen, the National Comprehensive Cancer Network suggests continuing pertuzumab with trastuzumab to complete the full course 1
No additional chemotherapy is needed after achieving pCR, according to the National Comprehensive Cancer Network 3
The National Comprehensive Cancer Network recommends adding endocrine therapy if the patient is hormone receptor-positive, starting after completion of all chemotherapy 1, 2

The National Comprehensive Cancer Network recommends trastuzumab 6 mg/kg IV every 3 weeks or trastuzumab 2 mg/kg IV weekly to complete 1 year total 1, 2
The total duration of HER2-targeted therapy should be 52 weeks (1 year) of trastuzumab-based therapy, according to the National Comprehensive Cancer Network 1, 2, 3

The National Comprehensive Cancer Network recommends starting endocrine therapy after completing all chemotherapy, given sequentially not concurrently, for patients with hormone receptor-positive disease 1, 2
Endocrine therapy can be given concurrently with HER2-targeted therapy (trastuzumab/pertuzumab), according to the Journal of Clinical Oncology 4, 5

The National Comprehensive Cancer Network recommends giving all chemotherapy before starting radiation therapy, except for CMF which can be concurrent 1, 2
HER2-targeted therapy (trastuzumab/pertuzumab) can continue during radiation, according to the National Comprehensive Cancer Network 1
Postmastectomy radiation is recommended for locally advanced disease, ≥4 positive nodes, or T3/T4 tumors, according to the National Comprehensive Cancer Network 6

The National Comprehensive Cancer Network advises against stopping trastuzumab early, as it must be completed for a full 1 year from neoadjuvant start 1, 2, 3
The National Comprehensive Cancer Network recommends against giving chemotherapy and endocrine therapy concurrently, as they should be given sequentially with endocrine therapy after chemotherapy 1, 2
The National Comprehensive Cancer Network advises against combining trastuzumab with anthracyclines, as it is associated with a 27% risk of cardiac dysfunction vs 8% with sequential therapy 2

The National Comprehensive Cancer Network recommends adjuvant chemotherapy with anthracycline-taxane regimen combined with dual HER2 blockade (trastuzumab plus pertuzumab) for 1 year, followed by radiation therapy if indicated, and endocrine therapy if hormone receptor-positive, for patients with HER2-positive invasive ductal carcinoma grade 3 7
Dual HER2 blockade with trastuzumab and pertuzumab provides a 24% relative reduction in recurrence risk (HR 0.76; 95% CI 0.64-0.91) with an absolute benefit of 4.5% at 6 years, for node-positive disease 7

For premenopausal patients with high-risk features, such as grade 3 or node-positive disease, the European Society for Medical Oncology recommends ovarian suppression (LHRH agonist) plus aromatase inhibitor as the preferred regimen 8

The American Society of Clinical Oncology recommends evaluating left ventricular ejection fraction (LVEF) prior to treatment initiation and every 3 months during HER2-targeted therapy, and permanently discontinuing trastuzumab if congestive heart failure develops or persistent/recurrent LVEF decline occurs 9

The National Comprehensive Cancer Network recommends considering extended anti-HER2 treatment with neratinib (240 mg daily for 1 year) after completing trastuzumab, particularly for hormone receptor-positive disease, which provides 2.3% absolute benefit in invasive disease-free survival 7
Neratinib causes diarrhea in 95% of patients, requiring prophylactic antidiarrheal protocol 7

For patients who completed trastuzumab-based adjuvant treatment ≤12 months before recurrence, the American Society of Clinical Oncology recommends following second-line HER2-targeted therapy recommendations (T-DM1 or trastuzumab deruxtecan); if recurrence occurs >12 months after completion, restarting first-line therapy (trastuzumab, pertuzumab, and taxane) is recommended 10, 11