Surgical treatment of borderline and malignant phyllodes tumors: the effect of the extent of resection and tumor characteristics on patient outcome.

INTRODUCTION: Malignant phyllodes tumors are rare fibroepithelial breast neoplasms. Appropriate surgical management remains a subject of debate. The purpose of our study was to define optimal surgical treatment and to identify factors associated with outcome.
METHODS: After confirmatory pathology review, we identified 67 patients with borderline (n = 15) and malignant (n = 52) phyllodes tumors treated at our institution between 1971 and 2008. We used Cox proportional hazards models to evaluate associations between treatment, patient and tumor characteristics, and disease-free (DFS) and cancer-specific survival (CSS).
RESULTS: Median patient age was 47 years. For 32 patients, definitive surgical treatment was wide local excision (WLE): 27 with margins ≥1 cm and 5 with margins <1 cm. Thirty-five underwent mastectomy. Two patients received radiotherapy after WLE and two after mastectomy with microscopically positive margins. After 10 years median follow-up, 16 patients (24 %) recurred locally (8 postmastectomy and 8 after WLE). Treatment type and margin extent did not impact local recurrence. Fifteen patients (22 %) developed distant disease. Overall 5-year DFS was 67.9 % and CSS 80.1 %. Tumor size >5 cm, mitotic rate ≥10/10 HPF, stromal overgrowth and cellularity (all p < 0.05) predicted DFS, whereas CSS was associated with the latter three variables. CSS was diminished for mastectomy patients who were significantly more likely to harbor tumors with adverse features.
CONCLUSIONS: With long-term follow-up, extent of surgical resection did not affect DFS for patients with borderline and malignant phyllodes tumors. Tumor features, most notably stromal overgrowth, were predictive of recurrence and survival, suggesting these high-risk patients may benefit from additional therapeutic strategies.