Late Brain Oligometastases Diagnosed at Least 36 Months after Cancer Detection are Associated with Favorable Survival Outcome

Objective The aim of this study was to investigate the impact of a long disease-free interval (at least 36 months from the first diagnosis of cancer) on survival in patients with brain oligometastases (maximum four lesions, no extracranial metastases). Methods This study involves a retrospective analysis in a group of 89 patients treated with different brain-directed approaches. Results We identified seven patients (8%) with an interval from cancer diagnosis to the development of brain metastases of at least 36 months. The median time interval was five months. The one-year survival rates were 80% (interval of at least 36 months) and 43% (shorter interval), respectively (p = 0.049). Correspondingly, a large difference in actuarial median survival was observed (39.9 months [95% confidence interval, 16.8-63.0 months] versus 9.7 months (95% confidence interval, 6.1-13.3 months). However, the two Kaplan-Meier curves were not statistically significantly different, p = 0.13. In addition to treatment-related differences, the two groups also differed with regard to the type of primary tumor (high versus low rates of non-small cell lung cancer) and gender. Conclusion Late dissemination was uncommon. The often applied strategy of effective local treatment for patients with brain-only oligometastases is warranted, especially if the disease-free interval had been at least 36 months. Larger studies are needed to fully understand the impact of confounding factors, such as gender and tumor biology.