Background: The objective of this study was to report on the incidence of and factors related to the occurrence of central nervous system metastases in a cohort of patients who were diagnosed with colorectal, lung, breast, or kidney carcinoma or melanoma.

Methods: Using the population-based Maastricht Cancer Registry (MCR), a cohort was created of patients with colorectal carcinoma (n = 720 patients), lung carcinoma (n = 938 patients), breast carcinoma (n = 802 patients), renal carcinoma (n = 114 patients), and melanoma (n = 150 patients). The patients had to live in the catchment area of the University Hospital Maastricht (UHM) and had to have been diagnosed at the UHM during the period 1986-1995. Patients with brain metastases were searched for by linking the MCR to the Neuro-Oncology Registry of the UHM. Radiology files were checked as well. Follow-up lasted until December 31, 1998.

Results: Brain metastases were diagnosed in 232 patients (8.5%) in the cohort (n = 2724 patients). Of these patients, 84 patients were diagnosed with brain metastases within 1 month after their primary diagnosis, 82 patients were diagnosed with brain metastases within 1 year of their primary diagnosis, and 66 patients were diagnosed with brain metastases more than 1 year after their primary diagnosis. The cumulative incidence after 5 years was estimated at 16.3% in patients with lung carcinoma, 9.8% in patients with renal carcinoma, 7.4% in patients with melanoma, 5.0% in patients with breast carcinoma, and 1.2% in patients with colorectal carcinoma. The incidence was lower in patients age > or = 70 years compared with younger patients (breast and lung carcinoma), lower in patients who were diagnosed before 1991 compared with patients who were diagnosed after 1991 (breast and lung carcinoma), and lower in patients who had nonsmall cell lung carcinoma compared with patients who had small cell lung carcinoma.

Conclusions: The frequency of brain metastases in this cohort was highest in patients with lung carcinoma, followed by patients with renal carcinoma. There was no evidence of an increasing incidence of brain metastasis in patients with carcinoma of the breast or lung.