As many as 15% of patients with cancer spread to their brains will have no obvious source, or primary tumor, of the cancer, according to Dr. Satoshi Maesawa and associates from the University of Pittsburgh, Pennsylvania. It's been unclear whether radiosurgery for such metastases is as effective as it is for brain tumors spread from a known primary tumor.
To help resolve this issue, the authors studied 15 patients who had radiosurgery for 31 brain tumors spread from an unknown primary site. Five patients also had evidence of cancer spread to sites other than the brain.
Primary tumors were ultimately detected in the lungs of three patients and in the liver of one patient, the authors report, but the source of the other brain tumors remained unknown in the remaining 11 patients.
All 27 brain tumors evaluated by CT scan shrank after radiosurgery, the investigators say, and eight tumors disappeared altogether. Only two tumors subsequently regrew to a measurable extent. Together, this represented an overall tumor control rate of 93% of tumors in 85% of patients.
Half the patients survived up to 15 months after radiosurgery (27 months after their first diagnosis), and 3 patients (20%) survived beyond 3 years, according to the report in the September 1st issue of Cancer.
Three of the patients died as a result of cancer that had spread to the brain, but only one of these deaths resulted from growth of the treated metastasis. Another nine patients, the researchers note, died from cancer outside the brain, despite control of their radiosurgically treated tumors.
The authors conclude that radiosurgery provides superior control of brain tumors from unknown primary cancers and leads to longer than expected survival in these patients.
SOURCE: Cancer 2000;89:1095-1101.