Progress of intracranial metastases during the interval before stereotactic radiosurgery, a retrospective cohort analysis

The incidence of intracranial metastatic disease is increasing worldwide. As a valuable treatment modality, stereotactic radiosurgery requires detailed imaging, and this study evaluated the differences between imaging obtained on the day of treatment compared to historical or referral imaging. A retrospective cohort study was performed, evaluating all the patients presenting with eligible referral imaging in a 13-month period and comparing this imaging to the imaging taken on the day of treatment. Numbers of additional metastases, volumes and volume differences among the images were compared. There was a median interval of 19 days between the acquisition of the diagnostic or referral scan and the day of treatment imaging. Even the group that had the shortest interval (up to 2 weeks) showed at least one additional deposit in 50 % of the patients. Volume was increased in 75 % of this group. Longer intervals were associated with higher increases in volume. These results demonstrate the increase in the disease burden in patients with intracranial metastatic disease, in relation to number and volume, in the interval between the referral and treatment imaging. This has significant implications for planning pathways, to ensure that metastatic deposits are not missed or undertreated.