Abstract P3-12-10: Overall survival in triple-negative breast cancers - Prognostic influence of type of surgery and adjuvant radiotherapy: A systematic review and meta-analysis

Abstract

Abstract BACKGROUND: Triple negative breast cancers (TNBC) are an aggressive, poorer prognostic tumour subtype which are negative for oestrogen, progesterone and human epidermal growth factor receptor 2 (HER-2) expression. Whilst the role of radiotherapy (RT) following breast conserving therapy (BCT) is widely accepted, there is no agreed consensus on the use of post-mastectomy RT, particularly in early-stage TNBC patients. METHODS: Four electronic databases were searched from their inception to April 2015 including PubMed, MEDLINE, EMBASE and web of science. Observational studies investigating overall survival and locoregional/distant recurrence outcomes in women with TNBC according to type of surgery and radiotherapy receipt were included. Authors were contacted directly for further data. A random effects model was used to pool study effect estimates using mastectomy (MT) only patients as the reference group. RESULTS: 8 studies including data from 3,456 patients were included. The median age and duration of follow-up was 54 years and 3.6 years respectively. The adjusted pooled hazard ratio (HR) and 95% confidence interval (CI) for overall survival comparing BCT and MT+RT to MT only was 0.52 (95% CI 0.31, 0.87; I2= 70.9%) and HR 0.60 (95% CI 0.38, 0.96; I2=41.5%) respectively. In subgroup analysis of MT+RT vs. MT alone, there was no significant interaction with early (T1-2, N0-1) vs. late stage (T3-4, N2-3) disease p=0.773 or age at diagnosis (<40, 40-64, ≥65 years) p=0.320. 5 studies evaluated local regional recurrence. Comparing BCT and MT+RT to MT only, the pooled HR was 0.61 (95% CI 0.41, 0.92) and HR 0.83 (95% CI 0.55, 1.26) respectively, with low heterogeneity detected (I2 0.0%). 4 studies assessed distant metastases. The pooled HR comparing BCT and MT+RT to MT only was 0.88 (95% CI 0.62, 1.23; I2= 0.0%) and HR 1.95 (95% CI 0.85, 4.49; I2= 75.1%) respectively. CONCLUSIONS: The addition of adjuvant radiotherapy appears to favourably impact overall survival, irrespective of the type of surgery received. BCT may reduce the risk of locoregional recurrence in comparison to MT only. The small number of contributing studies and often high study heterogeneity suggest cautious interpretation of the findings. Further epidemiological studies or pooled analyses of individual patient data are warranted. Citation Format: O'Rorke MA, Murray LJ, Bhoo Pathy N. Overall survival in triple-negative breast cancers - Prognostic influence of type of surgery and adjuvant radiotherapy: A systematic review and meta-analysis. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P3-12-10.