Stereotactic Radiosurgery for Resected Brain Metastases: Does the Surgical Corridor Need to be Targeted?

Although consensus guidelines for postresection stereotactic radiosurgery (SRS) for brain metastases recommend the surgical corridor leading to the resection cavity be included in the SRS plan, no study has reported patterns of tumor recurrence based on inclusion or exclusion of the corridor as a target. We reviewed tumor control and toxicity outcomes of postresection SRS for deep brain metastases based on whether or not the surgical corridor was targeted.

We retrospectively reviewed patients who had resected brain metastases treated with SRS between 2007 and 2018 and included only "deep" tumors (defined as located ≥1.0 cm from the pial surface before resection).

In 66 deep brain metastases in 64 patients, the surgical corridor was targeted in 43 (65%). There were no statistical differences in the cumulative incidences of progression at 12 months for targeting versus not targeting the corridor, respectively, for overall local failure 2% (95% confidence interval [CI], 0%-11%) versus 9% (95% CI, 1%-25%; P = .25), corridor failure 0% (95% CI, 0%-0%) versus 9% (95% CI, 1%-25%; P = .06), cavity failure 2% (95% CI, 0%-11%) versus 0% (95% CI, 0%-0%; P = .91), and adverse radiation effect 5% (95% CI, 1%-15%) versus 13% (95% CI, 3%-30%; P = .22). Leptomeningeal disease (7%; 95% CI, 2%-18%) versus 26% (95% CI, 10%-45%; P = .03) was higher in those without the corridor targeted.

Omitting the surgical corridor in postoperative SRS for resected brain metastases was not associated with statistically significant differences in corridor or cavity recurrence or adverse radiation effect. As seen in recent prospective trials of postresection SRS, the dominant pattern of progression is within the resection cavity; omission of the corridor would yield a smaller SRS volume that could allow for dose escalation to potentially improve local cavity control.