Abstract P5-08-13: Phyllodes tumours of the breast: The British Columbia cancer agency experience
Authors: MF Rodrigues, PT Truong, LM Weir, MA Knowling, ES Wai
Journal: Cancer Research (2017)

Abstract Background Phyllodes tumours (PT) of the breast are uncommon fibroepithelial lesions for which optimal management remains unclear. This population-based study reports treatment and outcomes for patients with PT and evaluates characteristics that influence outcome. Methods Data were analysed on 183 patients with newly diagnosed PT referred to the BC Cancer Agency from 1999-2014. Follow-up was obtained from chart and death records and letters to general practitioners. Five-year Kaplan-Meier (KM) local recurrence (LR) and survival were compared between cohorts with benign (n=83), borderline (n=50) and malignant PT (n=49) histology. Subtype was unknown in 1 patient who did not receive surgery due to severe comorbidity. Univariate analysis was performed using Cox regression modeling. Results Median follow-up was 65 (range 0.5-197) months. Median age was 48 (range 14–87) years. Median tumour size was 4 (range 1-23) cm. Heterologous sarcomatous differentiation was seen in 15 and malignant epithelial transformation in 11 patients. Local excision was performed in 163 (89%) and mastectomy in 19 (10%) patients. Margin status after local excision were: negative (&amp;gt;1mm, n=121, 74%), close (≤1mm, n=21, 13%), positive (tumour touching ink, n=20, 12%), or unknown (n=1, 1%). Margin status after mastectomy were negative (n=14, 74%) or close (n=5, 26%). Tumour borders were pushing (n=62, 34%), intermediate (n=22, 12%), infiltrative (n=38, 21%) or unknown (n=60, 33%). Eleven patients with malignant PT received radiation therapy as part of initial treatment. In these cases median tumour size was 8 cm and heterologous sarcomatous differentiation was present in 46% compared to 4 cm and 16% in malignant cases who did not receive RT. LR occurred in 16 cases (5 benign, 4 borderline and 7 malignant). Distant metastases (DM) occurred in 7 patients with malignant PT leading to 6 cause specific deaths. Five-year KM outcomes among women with benign, borderline, and malignant PT were: LR 6% vs 9% vs 21%, P=0.131; overall survival 96% vs 100% vs 82%, P=0.002; and disease free survival 94% vs 91% vs 67%, P&amp;lt;0.001. DM-free and cause specific survival at 5 years for malignant cases were 82% and 88% respectively. Five-year KM LR among women with negative vs close vs positive margins were 8% vs 6% vs 37%, P&amp;lt;0.001. Corresponding rates for intermediate vs pushing vs infiltrative borders were 6% vs 6% vs 33%, P=0.006. On univariate analyses, large tumour size, postmenopausal status, malignant classification, necrosis, positive margins, and infiltrative borders were factors associated with increased risk of any type of relapse (all P≤0.014). Positive margins and infiltrative tumour border were associated with increased LR (all P≤0.006), and the latter remained significant in exploratory analyses after adjusting for margin status and PT classification. Advanced age at diagnosis and large tumour size were predictors of DM (all P≤0.001). Conclusion In this population-based series, 5-year outcomes among women with PT are comparable to those reported in the literature. Exploratory analysis suggests that infiltrative tumour borders may be used in conjunction with margin status to assess LR risk. While close margin was not associated with increased LR, re-excision is warranted for cases with positive margins. Citation Format: Rodrigues MF, Truong PT, Weir LM, Knowling MA, Wai ES. Phyllodes tumours of the breast: The British Columbia cancer agency experience [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P5-08-13.