Malignant and borderline phyllodes tumors of the breast: a multicenter study of 362 patients (KROG 16-08).

Abstract

To identify risk factors for local recurrence (LR) and investigate roles of adjuvant local therapy for malignant and borderline phyllodes tumors of the breast. From 1981 to 2014, 362 patients with malignant (n = 235) and borderline (n = 127) phyllodes tumors were treated by breast-conserving surgery (BCS) or total mastectomy (TM) at 10 centers. Thirty-one patients received adjuvant radiation therapy (RT), and those who received adjuvant chemotherapy were excluded from the study. Median follow-up was 5years. LR developed in 60 (16.6%) patients. Regional recurrence occurred in 2 (0.6%) patientsand distant metastasis(DM) developed in 19 (5.2%) patients. Patients receiving BCS (p = 0.025) and those not undergoing adjuvant RT (p = 0.041) showed higher LR rates. For malignant subtypes, local control (LC) rates at 5 years for BCS alone, BCS with adjuvant RT, TM alone, and TM with adjuvant RT were 80.7, 93.3, 92.4, and 100%, respectively (p = 0.033). Multivariate analyses revealed BCS alone, tumor size≥ 5cm, and positive margins as independent risk factors for LR. Margin-positive BCS alone showed poorest LC regardless of tumor size (62.5%, p = 0.007). For margin-negative BCS alone, 5-year LC rates for tumors ≥ 5cm versus those < 5cm were 71.8% versus 89.5% (p = 0.012). For borderline subtypes, only positive margins (p = 0.044) independently increased the risk of LR. DM developed exclusively in malignant subtypes and a prior LR event increased the risk of DM by sixfold (HR 6.2, 95% CI 1.6-16.1, p = 0.001). Malignant and borderline phyllodes tumors with positive margins after surgery have high LR rates. After treatment by margin-negative BCS alone, patients with large malignant phyllodes tumors ≥ 5cm also have heightened risk of LR. Thus, such patients should be considered for additional local therapy.