What is the treatment for a malignant Phyllodes (periductal stromal) tumor?

Treatment of Malignant Phyllodes Tumor

The primary treatment for malignant phyllodes tumor is wide surgical excision with margins ≥1 cm, without axillary staging, followed by selective adjuvant radiotherapy for high-risk features. 1

Surgical Management

Wide excision with tumor-free margins of ≥1 cm is the definitive treatment for all malignant phyllodes tumors. 2, 1 This margin width is critical because local recurrence correlates directly with inadequate surgical margins, not with tumor grade or size. 3

Extent of Surgery

• Breast-conserving surgery (lumpectomy or partial mastectomy) is the preferred approach when adequate margins can be achieved. 1, 4, 5
• Mastectomy is indicated ONLY when tumor-free margins cannot be obtained with breast conservation, which is common with large tumors. 2, 1, 4
• For large malignant phyllodes tumors, breast conservation may not be feasible due to tumor size. 2

Critical Surgical Principles

• Do NOT perform axillary staging or sentinel lymph node biopsy - phyllodes tumors rarely metastasize to lymph nodes, and axillary surgery adds unnecessary morbidity without benefit. 2, 1, 6
• If margins are <1 cm after initial excision, re-excision should be performed to achieve adequate margins. 3, 4
• Narrow surgical margins (<1 cm) are associated with heightened local recurrence risk but are not an absolute indication for mastectomy if re-excision is feasible. 2

Adjuvant Radiotherapy

Adjuvant radiotherapy improves local control but NOT survival in malignant phyllodes tumors. 2

Indications for Radiotherapy (Category 2B)

Consider adjuvant radiotherapy for malignant phyllodes tumors with ANY of the following high-risk features: 2, 1

• Tumor size >5 cm
• Close margins (<5 mm) or positive margins despite re-excision attempts
• Infiltrative margins
• Multifocal disease
• Recurrent disease
• Any situation where additional recurrence would create significant morbidity (e.g., chest wall recurrence after salvage mastectomy)

Radiotherapy should follow the same principles applied to soft tissue sarcoma treatment. 2

Reconstruction Timing

Delayed reconstruction is strongly preferred over immediate reconstruction for large, high-grade malignant phyllodes tumors. 2

• Patients with large high-grade tumors are likely to receive postoperative chest wall radiotherapy and carry significant risk of local recurrence within the first two years. 2
• Reconstruction should be deferred until primary oncological management is completed and local recurrence risk has diminished. 2, 1

Systemic Therapy

Neither chemotherapy nor endocrine therapy has any proven role in the treatment of malignant phyllodes tumors. 1

• Although 58% contain estrogen receptors and 75% contain progesterone receptors, endocrine therapy does not reduce recurrence or death. 1
• No evidence shows that adjuvant cytotoxic chemotherapy reduces recurrence or death. 1
• The role of chemotherapy remains undefined and should not be routinely used. 6, 5

Management of Recurrence

Local Recurrence

• Re-excision with wide margins (≥1 cm) without axillary staging is the treatment for locally recurrent disease. 2, 1
• Consider postoperative radiotherapy if additional recurrence would create significant morbidity (e.g., after salvage mastectomy). 2

Distant Metastases

• Approximately 20% of patients with malignant phyllodes tumors develop distant metastases, most commonly to the lungs. 6, 5
• Metastatic disease should be managed following principles of soft tissue sarcoma, per NCCN Guidelines for Soft Tissue Sarcoma. 2
• Long-term survival with distant metastases is rare. 6

Multidisciplinary Management

Malignant phyllodes tumors should be referred to specialist sarcoma centers for pathology review and multidisciplinary team discussion. 2, 1

• Close collaboration between breast cancer and sarcoma multidisciplinary teams is necessary due to variation in clinical practice and improved outcomes in specialist centers. 2

Prognosis

• The 5-year disease-free survival rate for malignant phyllodes tumors is 66.1%. 1
• Margin status is more important than histologic subtype for predicting local recurrence. 1
• Local recurrence occurs in approximately 15% of patients overall and is more common after incomplete excision. 6

Critical Pitfalls to Avoid

• Do NOT perform routine axillary staging - this adds morbidity without benefit. 2, 1, 6
• Do NOT use adjuvant chemotherapy or endocrine therapy routinely - these have no proven efficacy. 1
• Do NOT routinely recommend radiotherapy for all malignant tumors - reserve for high-risk cases only. 2, 1
• Do NOT accept inadequate surgical margins - this is the most important modifiable factor for preventing local recurrence. 1, 3
• Do NOT perform immediate reconstruction in high-risk cases - delay until oncologic treatment is complete. 2, 1