Survival of older patients with metastasised breast cancer lags behind despite evolving treatment strategies--a population-based study.

BACKGROUND: Older women are more likely to be diagnosed with primary metastasised breast cancer than their younger counterparts. Evolving treatment strategies of metastasised breast cancer have resulted in improved survival in younger patients, but it remains unclear if this improvement has occurred in older patients as well. The aim of this study was to assess changes in treatment strategies over time in relation to overall and relative survival of older patients compared to younger patients with primary metastasised breast cancer. METHODS: All patients with a breast cancer diagnosis and distant metastases at first presentation (stage IV), between 1990 and 2012, were selected from the Netherlands Cancer Registry. Changes in treatment over time per age-group (<65 years, 65-75 years and >75 years) were assessed using logistic regression. Overall survival over time was calculated using Cox Regression Models and relative survival was assessed using the Ederer II method. RESULTS: Overall, 14,310 patients were included. Treatment strategies have strongly changed in the past twenty years; especially the use of chemotherapy has increased (P<0.001 in all age-groups). Overall survival of patients <65 has significantly improved (Hazard Ratio (HR) per year 0.98, 95% Confidence Interval (CI) 0.98-0.99, P<0.001), but the survival of older patients has not improved (HR 1.00, 95% CI 0.99-1.01, P=0.86 for patients aged 65-75 and HR 1.00, 95% CI 1.00-1.01, P=0.46 for patients aged >75). Similarly, relative survival has improved in patients <65 but not in women aged 65-75 and >75. CONCLUSION: Overall and relative survival of older patients with metastasised breast cancer at first presentation have not improved in recent years in contrast with the survival of younger patients, despite increased treatment with chemotherapy for women of all ages. Future studies should focus on stratification models that can be used to predict which patients may benefit from specific treatment options.