Survival Outcomes Among Patients with Metastatic Breast Cancer: Review of 47,000 Patients

Abstract

Background: Although metastatic breast cancer (MBC) remains incurable, advances in therapies have improved survival. Using a contemporary dataset of de novo MBC patients, we explore how overall (OS) and cancer-specific survival (CSS) changed over time.

Methods: All patients with de novo MBC from 1988 to 2016 were selected from Surveillance, Epidemiology, and End Results (SEER) 18. Unadjusted OS and CSS were estimated by Kaplan-Meier method and stratified by disease characteristics. Cox proportional hazards models determined factors associated with survival.

Results: 47,034 patients were included, with median OS of 25 months and CSS of 27 months. Survival steadily improved over time (1988: 1-year OS 62%, CSS 65%; 2015: 1-year OS 72%, CSS 74%). Patients with triple-negative breast cancer (TNBC) had the worst prognosis and were most likely to die from MBC [versus human epidermal growth factor receptor 2 (HER2)+ and hormone receptor (HR)+/HER2-]. Those with ≥ 4 sites of metastatic disease were also more likely to die from MBC with nearly identical OS and CSS (5-year OS 9%, CSS 9%), when compared with those with 1 site (5-year OS 31%, CSS 35%). After adjustment, improved CSS was associated with bone-only disease [hazard ratio (HR) 0.88, 95% confidence interval (CI) 0.83-0.94], while TNBC (versus HER2+: HR 3.12, 95% CI 2.89-3.36) and > 3 sites of metastatic disease (versus 1 site: HR 3.24, 95% CI 2.68-3.91) were associated with worse CSS (all p < 0.001).

Conclusions: Accurate prognostic estimates are essential for patient care. As treatments for patients with MBC have expanded, OS and CSS have improved, and more patients, particularly with limited distant disease or favorable tumor subtypes, are also dying from non-MBC causes.

FIG. 1.

Unadjusted OS and CSS for patients with metastatic breast cancer diagnosed in 1988–2016 from the SEER Program: a for the entire cohort, b OS stratified by year of diagnosis, and ≥ CSS stratified by year of diagnosis

FIG. 2.

Unadjusted OS (solid lines) and CSS (dotted lines) rates at 1-year (blue lines), 3-years (red lines), and 5-years (green lines) for patients with metastatic breast cancer from the SEER Program diagnosed in 1988–2016, stratified by year of diagnosis

FIG. 3.

Unadjusted OS (solid lines) and CSS (dotted lines) for patients with metastatic breast cancer from the SEER Program, diagnosed 2010–2016, stratified by tumor phenotype: HER2+ (blue lines), HR+/HER2− (red lines), and TNBC (green lines). HR+ estrogen receptor (ER) and/or progesterone receptor (PR) positive, TNBC ER-/PR-/HER2−.HR: hormone receptor. HER2: humanepidermal-growth-factor-receptor-2. TNBC: triple negative breast cancer

FIG. 4.

Unadjusted OS (solid lines) and CSS (dotted lines) for patients with metastatic breast cancer from the SEER Program, diagnosed 2010–2016, stratified by the number of metastatic sites: 1 (blue lines), 2 (red lines), 3 (green lines), and ≥ 4 (purple lines). one site = one organ system involved, irrespective of the number of the metastases within that organ system; two sites = two organ systems involved; etc.

FIG. 5.

Unadjusted OS (solid lines) and CSS (dotted lines) for patients with metastatic breast cancer from the SEER Program, diagnosed 2010–2016, stratified by proposed prognostic stage group: metastatic stage IVA (blue lines), IVB (red lines), and IVC (green lines)