Early detection of metachronous brain metastases by biannual brain MRI follow-up may provide patients with non-small cell lung cancer with more opportunities to have radiosurgery.

Purpose: Those who have brain metastases smaller than 30 mm in diameter and less than 5 in number can be treated less invasively with radiosurgery. This retrospective study evaluated the optimal brain magnetic resonance image (MRI) follow-up interval for non-small cell lung cancer (NSCLC) patients to detect radiosurgically manageable metachronous brain metastases (MBM).

Patients And Methods: The records of 551 patients with primary NSCLC, treated in our institute between 2002 and 2007, were reviewed. The initial brain MRI was performed within one month after diagnosis of NSCLC, and the follow-up brain MRI interval was at the discretion of physicians. The interval between the last MRI in which brain metastases were not found and the first MRI in which brain metastases were found was defined as the critical MRIs interval (CMI). The relationship between CMI and the maximum size or number of MBM was evaluated.

Results: Among reviewed patients, the initial MRI of 38 patients showed brain metastases and 29 patients were diagnosed as MBM. In these MBM patients, the median interval from diagnosis of NSCLC to diagnosis of brain metastases was 8.9 months. The median CMI was 4.7 (range: 1.6-18.9) months. All brain metastases smaller than 30 mm in maximum diameter were found when CMI was shorter than 6.0 months, although 5 or more brain metastases in number were detected even by shorter CMI than 3 months.

Conclusion: Early detection of MBM by biannual MRI follow-up may provide NSCLC patients with more opportunities to have less invasive treatment.