Early postoperative MRI after resection of brain metastases-complete tumour resection associated with prolonged survival.

Background: This study aimed to investigate the incidence of residual tumour after resection of brain metastases using early postoperative magnetic resonance imaging (MRI) and the influence of residual tumour on overall patient survival.

Methods: Data from 72 consecutive adult patients undergoing surgery for cerebral metastases over an 18-month study period were retrospectively collected. Early postoperative MRI was used to determine the presence of postoperative residual tumour. Patients were divided into three groups according to the presence of tumour remnant on early postoperative MRI: "no residual tumour", "non-measurable residual tumour" and "measurable residual tumour". Survival analysis (mean estimate survival time) was performed using the Kaplan-Meier and log-rank (mantel cox) tests and compared between groups. Surgical reports were evaluated with regard to the surgeon statement about intraoperative extent of resection (EOR) and compared with the presence of tumour remnant found on the early postoperative MRI.

Results: Sixty-eight procedures were followed by early postoperative MRI. MRI verified the presence of "measurable residual tumour" following 15 procedures (22%). MRI confirmed complete resection in 57%. Gross total resection was described by the operating surgeon in 85% of the procedures. There was a significant difference in survival time after surgery between the group having no residual tumour on MRI and the group with measurable residual tumour (p = 0.025). This difference could not be explained by the differences in postoperative radiation therapy. The longest survival was found in patients with non-measurable and no residual tumour on early postoperative MRI, who also received postoperative radiotherapy.

Conclusion: Residual tumour was seen on MRI after 22% of the procedures. The intraoperative assessment of EOR performed by the surgeon diverged from the early postoperative MRI in 40% of procedures. Correct assessment of residual tumour thus requires early postoperative MRI. Measurable residual tumour on early postoperative MRI was associated with shorter overall survival independent on postoperative radiotherapy.