Abstract P1-16-05: Prognosis and survival in metastatic breast cancer – Ten years in review, a population-based analysis
Authors: LeVasseur N , Fiorino L , Speers CH , Aparicio M , Lohrisch C , Chia SK 
Published: May 2019

Background: The rapidly evolving landscape of systemic treatment for metastatic breast cancer (MBC) during the 1990s led to meaningful improvements in the overall survival (OS) of MBC patients[1]. Despite ongoing and expanded access to new treatments, it remains unclear if this has translated into further advances in survival. Moreover, the prognosis of MBC patients based on subtype, over time, are also important to differentiate.

Methods: The BC Cancer Breast Cancer Outcomes Unit (BCOU) database was utilized to identify patients referred to BC Cancer who were diagnosed with MBC during 3 time cohorts (cohort 1:2003-2005; cohort 2:2007-2009; cohort 3:2011-2013), to reflect changes in MBC treatment over these separate time periods. Baseline clinical and pathological criteria were compiled, in addition to adjuvant treatments received, as well as number of lines of treatment in the metastatic setting. OS was compared across time cohorts for all patients and then between subtypes using Kaplan-Meier survival curves.

Results: A total of 3,953 patients met the inclusion criteria, consisting of 2,440 (61.7%) estrogen-receptor positive (ER+), 778 (19.7%) HER2 positive and 542 (13.7%) triple-negative breast cancer (TNBC) patients. One hundred and ninety-three patients (4.9%) were unable to be subtyped and were therefore excluded from the analysis . A total of 2,205 (90.4%) ER+ patients received at least 1 line of systemic therapy, with 80.0% receiving at least 1 line of hormonal therapy. The median time on hormonal treatment was 8.9 months (range 0.03 - 156.7) for first-line and 6.1 months (range 0.1 – 173.3) for second-line. In the HER2+ group, 665 (85.5%) patients received at least 1 line of treatment, with a median of 2 lines of treatment (range 1-16). Median duration of anti-HER2 treatment was 6.7 months (range 0.03 - 163.8) with a median of 1 line of anti-HER2 directed treatment (range 1-5). For TNBC patients, 357 (65.9%) received at least 1 line of treatment, with a median of 2 (range 1-10). No significant differences in OS were observed between the 3 time cohorts, with a median overall survival (mOS) of 1.63 years, 1.37 years and 1.57 years in cohorts 1-3, respectively (p=0.12).When comparing across subtypes, the ER+ group faired best with a mOS of 1.96 years (95% CI 1.8-2.1), consistent across time cohorts (p=0.72). This was followed by the HER2+ group with a mOS of 1.53 years (95% CI 1.3-1.7), also consistent across time cohorts (p=0.31). The TNBC group faired worst, with a mOS of 0.67 years (95% CI 0.6-0.8) over time (p=0.87).

Conclusions: Despite advances in systemic therapy since the early 2000s, no meaningful improvements in overall survival were observed over time, regardless of subtype. It remains to be seen if developments since 2013 will lead to gains in overall survival for MBC patients, at a real life, population-based level.

[1]Chia SK, Speers CH, D'yachkova Y, et al. Cancer 2007;110:973-979.

Citation Format: LeVasseur N, Fiorino L, Speers CH, Aparicio M, Lohrisch C, Chia SK. Prognosis and survival in metastatic breast cancer – Ten years in review, a population-based analysis [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P1-16-05.