Indications for Radiotherapy in Phyllodes Tumors
Adjuvant radiotherapy to the breast or chest wall should be strongly considered for malignant phyllodes tumors >5 cm, positive or close margins that cannot be re-excised, and recurrent disease where further recurrence would cause significant morbidity. 1, 2
Risk-Stratified Approach to Radiotherapy
Malignant Phyllodes Tumors
- Radiotherapy is strongly indicated for tumors >5 cm, as this threshold has demonstrated improved local control in multiple studies 2, 3
- Adjuvant RT improves local control but not overall survival in malignant phyllodes tumors 2
- A prospective multi-institutional study showed 0% local recurrence rate (95% CI: 0-8%) with margin-negative resection plus adjuvant RT, compared to historical rates of 20% with surgery alone 4
- For large malignant tumors (e.g., >13 cm), adjuvant radiotherapy to the chest wall should be strongly considered regardless of margin status 2
- Multivariate analysis demonstrates RT decreases locoregional failure risk (HR 0.12,95% CI 0.02-0.92, P=0.04) 5
Borderline Phyllodes Tumors
- Radiotherapy should be reserved for high-risk borderline cases only: specifically tumors >5 cm, infiltrative margins, or when clear margins cannot be achieved despite re-excision attempts 1
- Do not routinely recommend RT for all borderline tumors—this adds unnecessary morbidity without proven benefit in low-risk cases 1
- When margins are ≥1 cm in borderline tumors, excellent local control is achieved with surgery alone and RT is not indicated 6
Benign Phyllodes Tumors
- Radiotherapy has no role in benign phyllodes tumors when adequate surgical margins (≥1 cm) are achieved 6
Specific Clinical Scenarios Requiring Radiotherapy
Margin Status
- Positive or close margins (<5 mm) that cannot be re-excised warrant adjuvant RT 2, 3
- Attempt re-excision first if feasible, as margin status is the single most important factor for preventing local recurrence 2
- If re-excision would require mastectomy and the patient desires breast conservation, RT becomes essential 1
Recurrent Disease
- For locally recurrent phyllodes tumors, postoperative RT should be considered (category 2B) if additional recurrence would create significant morbidity, such as chest wall recurrence after salvage mastectomy 3
- This follows soft tissue sarcoma treatment principles 3
- Four patients who received RT for recurrent disease had no further recurrences in one series 5
Post-Mastectomy Radiotherapy
- Adjuvant RT should be discussed even after mastectomy for malignant phyllodes tumors, particularly for large tumors, as local control benefit persists 5
- This differs from epithelial breast cancer management and reflects the sarcoma-like behavior of these tumors 2
Radiation Technique and Dosing
- Target the breast or chest wall only—do not irradiate lymphatics, as phyllodes tumors rarely metastasize to lymph nodes (<1%) 2, 7
- Standard dose is 60 Gy to the breast/chest wall 7, 5
- Moderate dose-escalation (median BED 92.7 Gy) appears well-tolerated with no local recurrences observed in recent series 8
- Lower doses (50-60 Gy) may be equally effective, though dose-response relationship is not firmly established 7
Critical Pitfalls to Avoid
- Do not perform axillary staging or lymph node dissection—this is unnecessary and adds morbidity without benefit 1, 2
- Do not treat phyllodes tumors as epithelial breast cancer—they require sarcoma-directed management principles 2
- Delay reconstruction until after RT completion and when local recurrence risk has diminished (typically 2 years post-treatment) 2
- Do not skip RT in malignant tumors >5 cm based on negative margins alone—the size threshold independently predicts benefit 2, 4