What is the recommended treatment approach for a patient with breast cancer who did not receive Neoadjuvant Chemotherapy (NACT) prior to a Mastectomy (MRM)?

Treatment Approach for Breast Cancer Without Neoadjuvant Chemotherapy Prior to Mastectomy

For patients who undergo mastectomy without prior neoadjuvant chemotherapy, the postoperative treatment strategy should include adjuvant systemic therapy (chemotherapy and/or endocrine therapy based on tumor biology), radiation therapy based on pathologic findings, and targeted therapy for HER2-positive disease. 1

Postoperative Systemic Therapy

Chemotherapy Indications

• Adjuvant chemotherapy is indicated for node-positive breast cancer and selected node-negative patients based on tumor characteristics. 1
• Anthracycline-containing polychemotherapy regimens are the most efficacious standard treatment, superior to CMF (cyclophosphamide, methotrexate, fluorouracil). 1
• Chemotherapy should be started promptly after surgery, with a maximum of six cycles administered every 3-4 weeks. 1
• Premenopausal women derive greater benefit from adjuvant chemotherapy than postmenopausal women. 1

Endocrine Therapy

• Adjuvant tamoxifen (20 mg daily for 5 years) is beneficial for all patients with estrogen receptor-positive tumors, regardless of age. 1
• Tamoxifen should not be prescribed to patients with ER-negative tumors. 1
• For postmenopausal women with hormone receptor-positive disease, aromatase inhibitors are preferred over tamoxifen. 1
• Endocrine therapy should be administered sequentially after chemotherapy completion, not concurrently. 1

HER2-Targeted Therapy

• Up to 1 year of trastuzumab therapy must be completed for HER2-positive tumors (Category 1 recommendation). 1
• Trastuzumab may be administered concurrently with radiation therapy and endocrine therapy if indicated. 1

Postmastectomy Radiation Therapy (PMRT)

Definitive Indications (Category 1)

• PMRT to the chest wall and regional lymph nodes is mandatory for patients with 4 or more positive axillary lymph nodes. 1
• Radiation fields should include the chest wall and supraclavicular lymph nodes. 1

Strong Consideration (Controversial)

• For patients with 1-3 positive axillary lymph nodes, strongly consider chest wall and supraclavicular irradiation after chemotherapy. 1
• This recommendation is based on Danish Breast Cancer Collaborative Group data showing substantial survival benefit, though some studies show contradictory results. 1
• Women with 1-3 positive nodes AND tumors >5 cm OR positive pathologic margins should definitely receive PMRT. 1

Internal Mammary Node Irradiation

• Including internal mammary lymph nodes in the radiation field can be considered (Category 3), though this remains controversial among experts. 1
• Consider internal mammary field radiation in women with positive axillary nodes. 1

Optional Scenarios

• Postmastectomy radiation therapy in patients with T2N0M0 tumors may be considered optional. 1

Sequencing of Therapies

The proper sequence is critical for optimal outcomes:

• Surgery (mastectomy with axillary staging) → Chemotherapy → Endocrine therapy → Radiation therapy can be given concurrently with endocrine therapy and trastuzumab. 1
• Chemotherapy and endocrine therapy must be given sequentially, with endocrine therapy following chemotherapy completion. 1
• Trastuzumab and endocrine therapy can be administered concurrently with radiation therapy. 1

Breast Reconstruction Considerations

• Immediate breast reconstruction may be performed at the time of mastectomy. 1
• The choice of immediate reconstruction should not compromise optimal use of locoregional radiotherapy and systemic treatment. 1
• After axillary dissection, radiotherapy to the axilla should be avoided due to increased risk of locoregional complications. 1

Common Pitfalls to Avoid

• Do not omit postoperative chemotherapy in patients who would have been candidates for adjuvant chemotherapy based on tumor characteristics. 1
• Do not prescribe tamoxifen to patients with ER-negative tumors, as it provides no benefit. 1
• Do not delay initiation of adjuvant chemotherapy, as prompt treatment is associated with better outcomes. 1
• Do not base radiation therapy decisions solely on tumor size; nodal status is the primary determinant for PMRT. 1
• Do not administer chemotherapy and endocrine therapy concurrently; they must be given sequentially. 1

Surveillance After Treatment

• History and physical examination every 4-6 months for 5 years, then annually. 1
• Mammography every 12 months. 1
• Women on tamoxifen require annual gynecologic assessment if uterus is present. 1
• Women on aromatase inhibitors or experiencing treatment-induced ovarian failure should have bone mineral density monitoring at baseline and periodically thereafter. 1