Abstract PD6-02: Local recurrence in young women with invasive breast cancer; the prospective study of outcomes in sporadic and hereditary breast cancer (POSH)

Abstract

Abstract Aim To evaluate the surgical and clinical factors affecting local recurrence and other outcomes in young breast cancer patients using the POSH study. Background POSH (MREC:00/06/69) is a prospective cohort study of 3024 women aged 18-40 with breast cancer. Randomized controlled trials suggest equivalent survival between mastectomy and breast conserving surgery (BCS); however, very few young patients were included in these analyses. Emerging data also suggests a possible survival advantage for mastectomy in gene mutation carriers, and young age may be a predictor of higher rates of local recurrence. Methods Summary statistics were used to describe the cohort by surgical type (mastectomy or BCS). Study endpoints were in-breast ipsilateral local-recurrence interval, distant disease-free interval and overall survival. Cumulative hazard and Kaplan-Meier plots were used to describe survival data. Univariable and multivariable analyses were carried out using Cox proportional hazards models and flexible parametric survival (FPS) models (for any models with time-varying covariates). Results Of 2882 patients analysed, 1464 underwent mastectomy, 1395 BCS; and 23 had lymph node surgery only. Patients undergoing mastectomy had significantly larger tumours and higher proportions of positive Family History, positive estrogen receptor (ER+), progesterone receptor (PR+) and/or human epidermal growth factor 2 (HER2+) tumours. Local events only accounted for 15% of recurrences. Local recurrence varied over time by surgical type; local recurrence rate was similar at 18 months but higher for BCS compared to mastectomy at 5- and 10-years (18-months: 1.0% vs 1.0%, FPS-HR[95%CI]=1.43[0.89,2.32], p=0.348; 5-years: 5.3% vs 2.6%, FPS-HR[CI]=3.39[2.03,5.66], p<0.001; and 10-years: 11.7% vs 4.9%, FPS-HR[CI]=5.27[2.43,11.43], p<0.001, respectively). Similar results were found in the adjusted model and when restricting the analyses to patients with smaller tumours. Conversely, distant-metastases and death events were significantly lower for BCS but not after adjusting for prognostic factors. Chest-wall radiotherapy following mastectomy was associated with improved local recurrence interval (HR[CI]=0.46[0.24,0.86],p=0.015). Positive surgical margins, and the development of a local event, predicted for reduced distant disease free interval (HR[CI]=0.50[0.35,0.71],p<0.001; and 10-year FPS-HR[CI]=0.29[0.14,0.62],p=0.001, respectively). Conclusions In the short term, there is no difference in local recurrence between BCS and mastectomy in young women. Longer term, local recurrence is higher in BCS, but there is no difference in survival between surgical groups after adjusting for known prognostic factors. Surgical extent appears to be less important for distant relapse or death from breast cancer than completeness of excision or, where appropriate, chest-wall radiotherapy. Acknowledgements Data collection/analysis funded by CRUK (grants:A7572,A11699,C1275/A15956). Sponsored by UHS NHS Foundation Trust. Citation Format: Maishman T, Cutress RI, Hernandez A, Gerty S, Copson ER, Durcan L, Eccles DM. Local recurrence in young women with invasive breast cancer; the prospective study of outcomes in sporadic and hereditary breast cancer (POSH) [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 PD6-02.