Treatment outcomes and patients’ characteristics of malignant phyllodes breast neoplasms: A tertiary care center experience.

Abstract

e13159 Background: Phyllodes tumors (PTs) are rare breast neoplasms (<1% of breast tumors), classified as benign, borderline, or malignant. Surgical excision is the primary treatment, with radiotherapy (RT) and chemotherapy's roles remain controversial. This study evaluates patient characteristics and outcomes of borderline and malignant PT in a tertiary center. Methods: Female patients with histologically confirmed borderline or malignant PT of the breast, diagnosed at King Hussein Cancer Center between 2012 and 2022, were included. Patients who underwent surgery (wide local excision or mastectomy) may have received radiotherapy (RT) based on post-surgical margin status (close <1 cm or positive) and histopathological features (necrosis, malignancy grade). Oncologic outcomes included disease-free survival (DFS), overall survival (OS), local recurrence, and distant metastasis. Results: A total of 61 cases were included, with a median age of 43 years. PTs were malignant in 44 (72%) patients and borderline in 17 (28%). Median follow-up for the cohort was 25 months. Case fatality was 21%, and distant metastasis (34%) occurred only in patients with malignant PT. RT group patients had higher rates of malignant PT (89% vs. 59%; p = 0.005), necrosis (37% vs. 12%; p = 0.01), and close margins (70% vs. 53%; p = 0.04). On multivariable Cox proportional hazards model (CPH), malignant PT compared to borderline was associated with worse DFS (HR = 1.57, 95% CI: 1.25–1.97, p < 0.001). Similarly, the presence of necrosis (HR = 1.73, 95% CI: 1.41–2.12, p < 0.001) was a significant predictor of inferior DFS. Patients who received radiotherapy also had a higher risk for relapse or death compared to those who did not (HR = 1.35, 95% CI: 1.08–1.68, p = 0.012). However, close surgical margins, compared to negative margins, were associated with a non-significant increase in risk (HR = 1.22, 95% CI: 0.95–1.56, p = 0.153). For OS, malignant PT (HR = 1.85, 95% CI: 1.42–2.40, p < 0.001) and necrosis (HR = 1.92, 95% CI: 1.53–2.41, p < 0.001) increased mortality risk. RT modestly elevated OS risk (HR = 1.28, 95% CI: 1.02–1.60, p = 0.031). Margin status (close vs. negative) showed no significant effect on OS (HR = 1.15, 95% CI: 0.88–1.49, p = 0.3). Conclusions: Predictors of poor outcomes in PT include malignant subtype compared to borderline and positive necrosis. Given its rarity, multi-institutional studies are needed to understand its prevalence, biological behavior and optimal therapeutic approach. Malignant PT Borderline PT p-value Number of Patients (n) 44 17 Average Tumor Size (cm) 10.05 7.08 < 0.001 Necrosis 30% (13/44) 6% (1/17) < 0.05 Mastectomy 73% (32/44) 41% (7/17) < 0.05 Wide Local Excision 27% (12/44) 59% (10/17) <0.05 Close Margins (<1cm) 64% (28/44) 53% (9/17) 0.40 Local Recurrence 14% (6/44) 6% (1/17) 0.40