Brain metastases are being seen with increasing fre- quency in hospital-based studies and surgical series. 2,11 Since 1972, no population-based studies have been con- ducted in the United States in which the incidence of brain metastases is addressed. 19 An increase in the ratio of brain metastases to primary tumors in hospital-based series and surgical series has been noted. This could be related to a number of factors including improved treatment of prima- ry cancer and systemic metastases resulting in an increase in survival times that, in turn, may provide time for cells sequestered in a protective "sanctuary" behind the blood– brain barrier to multiply and become symptomatic. 13,17,18 In addition, with an aging population, more people are at risk for developing primary systemic cancer, and as a re- sult, the number of brain metastases will also increase. Finally, a greater awareness on the part of physicians of the favorable brain metastases–related management strategies coupled with improved neuroimaging capability have also contributed to the increased incidence of diag- nosed brain metastases. 3,4,7,15 There are only three population-based published studies on the incidence of metastatic tumors of the brain. The only study recorded in the United States was performed at the Mayo Clinic and published in 1972. The other studies were conducted in Scandinavian countries, 8,9 the last be- ing reported in 1984. Therefore, all of these studies in- volved people of predominantly Scandinavian origin as opposed to the more diverse ethnic distribution usually encountered in North American clinical practice. These studies also antedate the development of more sophisti- cated methods of neurodiagnostic imaging. In conjunction with the apparent increase in the inci- dence of brain metastases, there has been a willingness to treat such lesions more aggressively. 6 For the purposes of developing clinical trials and determining allocation of resources, studies designed to determine the incidence of brain metastases and patient survival in a defined popula- tion have become important. In this project, we focus on the incidence of synchronous brain metastases and the survival of patients harboring these lesions. CLINICAL MATERIAL AND METHODS The SEER Program of the United States National Can- Neurosurg Focus Preview: J Neurosurg 93:December 2000, Click here to return to Table of Contents Survival of patients with synchronous brain metastases: an epidemiological study in southeastern Michigan AJITH J. THOMAS, M.D., JACK P. ROCK, M.D., CHRISTINE C. JOHNSON, PH.D., LINDA WEISS, PH.D., GORDON JACOBSEN, M.S., AND MARK L. ROSENBLUM, M.D. Departments of Neurosurgery and Cancer Epidemiology Prevention and Control, Josephine Ford Cancer Center Henry Ford Health System, Barbara Karmanos Cancer Center, Detroit, Michigan; and Biostatistics and Research Epidemiology, Henry Ford Health System, Detroit, Michigan Object. It has been suggested that synchronous brain metastases (that is, those occurring within 2 months of prima- ry cancer diagnosis) are associated with a shorter survival time compared with metachronous lesions (those occurring greater than 2 months after primary cancer diagnosis). In this study the authors used data obtained from the National Cancer Institute's Surveillance, Epidemiology, and End Results Program to determine the incidence of synchronous brain metastases and length of survival of patients in a defined population of southeastern Michigan residents. Methods. Data obtained in 2682 patients with synchronous brain metastases treated from 1973 to 1995 were re- viewed. Study criteria included patients in whom at least one brain metastasis was diagnosed within 2 months of the diagnosis of primary cancer and those with an unknown primary source. The incidence per 100,000 increased five- fold, from 0.69 in 1973 to 3.83 in 1995. The most frequent site for the primary cancer was the lung (75.4%). The sec- ond largest group (10.7%) consisted of patients in whom the primary site was unknown. The median survival length was 3.3 months. There was no significant difference in the median survival in patients with primary lung/bronchus and those with an unknown primary site (3.2 months and 3.4 months, respectively). Conclusions. Patients who present with synchronous lesions have a poor prognosis, and the predominant cause of death, in greater than 90% of cases, is related to systemic disease; however, despite poor median survival lengths, cer- tain patients will experience prolonged survival. KEY WORDS • epidemiology • synchronous • brain metastasis • survival Neurosurg. Focus / Volume 9 / August, 2000 1 Abbreviations used in this paper: CT = computerized tomogra- phy; SEER = Surveillance, Epidemiology, and End Results.