Brain metastases in patients with no known primary tumor

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Abstract
The care of patients with a brain metastasis from unknown primary site is controversial. The authors reviewed the results of stereotactic radiosurgery in this group of patients to better define clinical expectations. During an 11-year interval, radiosurgery was performed in 421 patients with brain metastases at the University of Pittsburgh. Fifteen patients had solitary or multiple (≤ 5) brain metastases without a detectable primary site at the time of initial presentation. In five patients, a histologic diagnosis of cancer was obtained from extracranial metastatic sites. In 10 patients, a diagnosis was obtained from the brain. A total of 31 tumors with a mean volume of 4.3 mL (range, 0.05–18.6 mL) underwent radiosurgery with a mean marginal dose of 16.2 Gray (Gy) (range, 12–20 Gy). Fourteen patients (93.3%) also received whole brain fractionated radiation therapy. The median survival was 15 months after radiosurgery (range, 1–48 months) and 27 months after their initial diagnosis of cancer. In 4 patients (26.7%), the primary tumor was discovered later (lung in 3 patients and liver in 1). Three of these four patients died due to progression of their primary tumor. Of the remaining 11 patients, 4 died of progression of extracranial metastases, 2 died of other systemic diseases, and 3 patients died because of progression of brain metastasis. Three patients (20%) were still living between 21–48 months after radiosurgery. The presence of active systemic disease and brain stem location both were associated with a poor outcome (P = 0.004 and 0.04). The actuarial imaging-defined local tumor control rate was 91.3 ± 5.9% at 4 years. Radiosurgery was an effective strategy for patients with brain metastases from an unknown primary site. Disease progression outside of the brain was the usual cause for patient death. Cancer 2000;89:1095–1101. © 2000 American Cancer Society.