What is the treatment for myxoid sarcoma of the breast?

Treatment of Myxoid Sarcoma of the Breast

Myxoid sarcoma of the breast should be managed at a specialist sarcoma center with wide surgical excision to achieve clear margins, followed by adjuvant radiotherapy for tumors >5 cm or with close/positive margins, and consideration of chemotherapy only in the metastatic/advanced disease setting. 1, 2

Multidisciplinary Referral and Management

• All breast sarcomas must be referred to specialist sarcoma centers for pathology review and multidisciplinary team (MDT) discussion involving both breast cancer and sarcoma specialists. 1
• Close collaboration between breast cancer MDT and sarcoma MDT is essential for optimal management. 1

Surgical Approach

Primary Surgical Treatment

• Wide excision with clear (negative) margins is the cornerstone of treatment and the most important prognostic factor for local control and overall survival. 2, 3, 4
• Either breast-conserving surgery (BCS) or mastectomy can be performed, depending on tumor size relative to breast size and ability to achieve clear margins. 1
• Negative surgical margins are more critical than the extent of resection (mastectomy vs. quadrantectomy). 3, 4

Axillary Management

• Axillary staging by sentinel node biopsy is NOT required for breast sarcomas, unlike epithelial breast cancers, as lymph node metastases are extremely rare in most sarcoma subtypes. 2, 5

Reconstruction Considerations

• For large, aggressive primary breast sarcomas requiring mastectomy, reconstruction should be delayed rather than immediate, as patients with large high-grade tumors will likely receive postoperative chest wall radiotherapy and carry significant risk of local recurrence within the first two years. 1

Adjuvant Radiotherapy

• Adjuvant radiotherapy improves local control but NOT survival in breast sarcomas. 1, 2
• Radiotherapy should be considered for:
  • Tumors >5 cm 1, 3
  • Close margins (<5 mm) or positive margins 1
  • High-grade tumors 1
  • Multifocal or recurrent disease 1
• Neoadjuvant radiotherapy does NOT have a role in breast sarcomas. 1

Chemotherapy Considerations

When to Consider Chemotherapy

• Chemotherapy should only be considered in the metastatic/advanced disease setting, following the same principles as adult-type soft tissue sarcomas. 2
• Neoadjuvant chemotherapy should be considered when tumors are large and difficult to resect with clear margins, to shrink the tumor and facilitate negative margin resection. 3
• Tumor size >5 cm is associated with elevated risk of systemic failure and poor prognosis, making these patients candidates for systemic therapy. 3, 5

First-Line Chemotherapy Options

• Single-agent doxorubicin (75 mg/m² every 3 weeks) is the standard first-line treatment for metastatic soft tissue sarcomas, including breast sarcomas. 2
• The cumulative dose of doxorubicin should not exceed 240 mg/m² in two-drug regimens to minimize cardiotoxicity. 2
• Combination chemotherapy produces only marginal increases in response rates with increased toxicity and no survival improvement compared to single-agent doxorubicin. 2

Histology-Specific Considerations for Myxoid Sarcomas

• While the evidence focuses primarily on angiosarcoma and other breast sarcoma subtypes, myxoid sarcomas should be treated according to general soft tissue sarcoma principles. 2, 3
• After first-line anthracycline failure, trabectedin is a second-line option, particularly effective in leiomyosarcoma and liposarcoma subtypes. 2

Prognostic Factors

• Tumor size >5 cm is the most significant prognostic indicator, with 5-year overall survival of 83% for tumors <5 cm versus 42% for tumors >5 cm. 5
• Negative surgical margins are critical for both local recurrence and overall survival. 3, 4
• Local recurrence rates are high, and metastatic disease development is associated with poor outcomes. 5

Common Pitfalls to Avoid

• Do not perform axillary staging as it is not indicated and provides no benefit in breast sarcomas. 2, 5
• Do not pursue immediate reconstruction in patients with large or high-grade tumors who will require postoperative radiotherapy. 1
• Do not use neoadjuvant radiotherapy as it has no established role in breast sarcomas. 1
• Do not use combination chemotherapy routinely as it increases toxicity without survival benefit compared to single-agent doxorubicin. 2