Numerous patients with few brain metastases receive radiosurgery, either alone or in combination with whole-brain irradiation. The addition of whole-brain irradiation to radiosurgery reduces the rate of intracerebral failures, particularly the development of new cerebral lesions distant from those treated with radiosurgery. Less intracerebral failures mean less neurocognitive deficits. However, whole-brain irradiation itself may lead to a decline in neurocognitive functions. Therefore, a number of physicians have reservations with regard to adding whole-brain irradiation to radiosurgery. Prognostic factors that allow an estimation of the risk of developing new cerebral metastases can facilitate the decision regarding additional whole-brain irradiation. Since primary tumors show a different biology and clinical course, prognostic factors should be identified separately for each primary tumor leading to brain metastasis. The present study investigated 10 characteristics in a series of 98 patients receiving radiosurgery alone for 1-2 cerebral metastases from lung cancer, the most common primary tumor associated with brain metastasis. These characteristics included radiosurgery dose, age, gender, performance status, histology, number of cerebral lesions, maximum total diameter of cerebral lesions, main location of cerebral lesions, extracranial spread and interval from first diagnosis of lung cancer to administration of radiosurgery. On univariate analysis, the number of cerebral lesions prior to radiosurgery (1 vs. 2 lesions) was the only characteristic significantly associated with freedom from new brain metastases (P=0.002). In cases of 2 lesions, 73% of patients developed new cerebral lesions within 1 year. On multivariate analysis, the number of brain metastases remained significant (risk ratio, 2.46; 95% confidence interval, 1.34-4.58; P=0.004). Given the high rates of new cerebral lesions in patients with 2 brain metastases, these patients should be strongly considered for additional whole-brain irradiation.
