Incidence and time trends of brain metastases admissions among breast cancer patients in Sweden

BACKGROUND: While treatment for breast cancer has been refined and overall survival has improved, there is concern that the incidence of brain metastases has increased. METHODS: We identified patients in Sweden with incident breast cancer 1998–2006 in the National Cancer Register, and matched these to the National Patient Register to obtain information on hospital admissions for distant metastases. Hazard ratios (HRs) and 95% confidence intervals (CIs) were computed with Cox regression as estimates of relative risk. RESULTS: Among 50 528 breast cancer patients, 696 (1.4%) were admitted with brain metastases during median 3.5 years of follow-up. Admissions for other metastases were found in 3470 (6.9%) patients. Compared with the period 1998–2000, patients diagnosed with breast cancer 2004–2006 were at a 44% increased risk of being admitted with brain metastases (HR 1.44, 95% CI 1.13–1.85). CONCLUSION: The incidence of admissions with brain metastases in breast cancer patients was increasing in the mid-2000s in Sweden. These findings support a true increase in incidence of brain metastases among breast cancer patients.