How long should hormonal therapy be continued in patients with HER2-positive invasive ductal carcinoma?

Duration of Hormonal Therapy in HER2-Positive, Hormone Receptor-Positive Invasive Ductal Carcinoma

For patients with HER2-positive and hormone receptor-positive invasive ductal carcinoma, endocrine therapy should be continued for 5-10 years total from diagnosis, independent of HER2-targeted therapy completion, which is limited to 1 year (52 weeks). 1, 2

HER2-Targeted Therapy Duration

• Complete 1 year (52 weeks) of trastuzumab-based therapy total, counting from the start of neoadjuvant therapy if applicable 1, 2
• For patients who received dual HER2 blockade (trastuzumab plus pertuzumab) in the neoadjuvant setting and achieved pathologic complete response, continue both agents to complete the full 1-year course 1
• HER2-targeted therapy is NOT continued beyond 1 year in the adjuvant setting 1
• The only exception is extended adjuvant neratinib (240 mg daily for 1 year) after completing trastuzumab, which can be considered for hormone receptor-positive disease, providing 2.3% absolute benefit in invasive disease-free survival 1

Endocrine Therapy Duration and Sequencing

• Start endocrine therapy after completing all chemotherapy - these should be given sequentially, never concurrently 1, 2
• Endocrine therapy CAN be given concurrently with HER2-targeted therapy (trastuzumab/pertuzumab) 1
• Continue endocrine therapy for 5-10 years total from diagnosis, which extends well beyond the 1-year HER2-targeted therapy duration 1, 2
• For premenopausal patients with high-risk features (grade 3 or node-positive disease), ovarian suppression (LHRH agonist) plus aromatase inhibitor is the preferred regimen 1, 2
• For postmenopausal patients, aromatase inhibitors are the preferred initial endocrine therapy 2

Advanced/Metastatic Disease Context

In the metastatic setting, the approach differs significantly:

• Continue HER2-targeted therapy indefinitely until progression or unacceptable toxicity 3
• When chemotherapy is stopped after 4-6 months (or at maximal response), continue HER2-targeted therapy without interruption 3
• For hormone receptor-positive, HER2-positive metastatic disease, endocrine therapy plus HER2-targeted therapy (trastuzumab or lapatinib) provides progression-free survival benefit 3
• The optimal duration of anti-HER2 therapy for metastatic disease is unknown, but it should continue beyond chemotherapy cessation 3
• In patients achieving complete remission in the metastatic setting, stopping anti-HER2 therapy after several years of sustained complete remission may be considered, particularly if treatment re-challenge is available upon progression 3

Critical Distinction: Adjuvant vs. Metastatic

The question context suggests adjuvant therapy for invasive ductal carcinoma, where:

• HER2-targeted therapy = 1 year fixed duration 1, 2
• Endocrine therapy = 5-10 years total 1, 2

This contrasts sharply with metastatic disease, where HER2-targeted therapy continues indefinitely 3

Common Pitfalls to Avoid

• Do not stop trastuzumab early - the full 52 weeks must be completed from neoadjuvant start 1
• Do not give chemotherapy and endocrine therapy concurrently - they must be sequential with endocrine therapy starting after chemotherapy completion 1, 2
• Do not confuse adjuvant and metastatic treatment durations - adjuvant HER2 therapy is time-limited (1 year), while metastatic HER2 therapy continues until progression 3, 1
• Do not stop endocrine therapy when HER2-targeted therapy ends at 1 year - endocrine therapy continues for years beyond this point 1, 2