Progression of the lung cancer primary correlates with the identification of new brain metastases after initial radiosurgery

We retrospectively evaluated the relationship between the response of lung lesions and distant progression-free survival (DPFS) after radiosurgery in patients with brain metastases. A total of 47 consecutive patients were treated with radiosurgery for brain metastases. Distant progression was defined as a new enhancing intracranial tumor or leptomeningeal enhancement noted on follow-up magnetic resonance imaging. Progression of lung lesions was defined as follows: (1) a 20% increase in the summed diameter of the target lesions; (2) an absolute increase of 5 mm when the summed diameter was very small; or (3) detection of new lesions in the lung. Distant progression after radiosurgery was observed for twenty-one (44.7%) patients; we observed development of new distant metastases in nine patients, development of leptomeningeal seeding in eight patients, and combined failure of distant progression and local control failure in four patients. Forty-two (89.4%) patients had lung lesions at the time of radiosurgery, and progression of their lung lesions during the post-radiosurgery follow-up period was observed for 18 (38.3%) of these. The median DPFS was 7.00 months (95% CI, 6.153–7.847). Actuarial DPFS 3, 6, and 12 months after radiosurgery was 81.5, 61.3, and 36.7%, respectively. In multivariate analysis, only the criterion progression of lung lesions reached statistical and independent significance (P = 0.021, OR = 3.372, 95% CI, 1.200–9.480). The response of lung lesions after radiosurgery is likely to be a good predictor of DPFS after radiosurgery in patients with brain metastases.