Should a patient with Stage 3A Her2 positive breast cancer, with significant response to chemotherapy, undergo MRM and axillary lymph node dissection?

Management of Stage 3A HER2-Positive Breast Cancer with Complete Clinical Response to Chemotherapy

Despite the complete clinical response to chemotherapy with an immeasurable tumor, this patient with Stage 3A HER2-positive breast cancer should still undergo modified radical mastectomy (MRM) and axillary lymph node dissection (ALND) to ensure optimal local control and survival outcomes. 1

Rationale for Surgical Management After Complete Clinical Response

Mastectomy Recommendation

• Complete clinical response does not guarantee complete pathological response
• NCCN guidelines recommend that for stage IIIA breast cancer, local therapy after preoperative systemic therapy typically consists of total mastectomy with level I/II axillary lymph node dissection 2
• Non-delineated masses after chemotherapy represent incomplete response to neoadjuvant therapy, suggesting chemoresistant disease that requires definitive surgical removal 1
• Breast-conserving surgery is not considered a standard approach for stage 3A disease, particularly when the mass remains non-delineated after chemotherapy 1

Axillary Management

• If sentinel lymph node biopsy (SLNB) was performed pre-chemotherapy and was positive, a level I/II axillary lymph node dissection should be performed 2
• If SLNB was not performed pre-chemotherapy, a complete axillary lymph node dissection is recommended for stage IIIA disease 2
• If SLNB was performed pre-chemotherapy and was negative, further axillary lymph node staging is not necessary 2

Post-Surgical Adjuvant Therapy

HER2-Targeted Therapy

• Complete up to 1 year of trastuzumab therapy (category 1 recommendation) for HER2-positive tumors 2, 1
• If the patient has already received pertuzumab/trastuzumab in the neoadjuvant setting, continue HER2-targeted therapy to complete a full year 1

Radiation Therapy

• Post-mastectomy radiation therapy to chest wall and regional lymph nodes is strongly recommended for stage 3A disease 1
• Radiation should be delivered to the chest wall and supraclavicular lymph nodes 2
• Consider radiation therapy to internal mammary nodes (category 3) 2

Endocrine Therapy

• If the tumor is ER and/or PR positive, endocrine therapy should be administered 2
• Endocrine therapy can be administered concurrently with radiation therapy if indicated 2

Potential Pitfalls and Caveats

• Clinical vs. Pathological Response: Clinical complete response does not always correlate with pathological complete response. Studies show that even with clinical complete response, residual disease is often found in mastectomy specimens 3

• Risk of Recurrence: Local recurrence rates are higher when definitive surgery is omitted, even with apparent complete clinical response 4

• Surgical Margins: Negative surgical margins are critical for local control, which is more reliably achieved with mastectomy in stage IIIA disease 5

• Reconstruction Options: Immediate or delayed reconstruction can be considered based on patient factors and planned adjuvant therapy 1

In conclusion, despite the excellent response to neoadjuvant chemotherapy, current guidelines and evidence strongly support proceeding with MRM and ALND for this patient with stage 3A HER2-positive breast cancer to optimize local control and survival outcomes.