Surgical Technique and Clinically Relevant Resection Cavity Dynamics Following Implantation of Cesium-131 Brachytherapy in Patients With Brain Metastases

Abstract

BACKGROUND: 

Cesium-131 (Cs-131) brachytherapy is used to reduce local recurrence of resected brain metastases. To ensure dose homogeneity and reduce risk of radiation necrosis, interseed distance and cavity volume must remain stable during delivery.

OBJECTIVE: 

To investigate the efficacy of the “seeds-on-a-string” technique with intracavitary fibrin glue in achieving cavity volume stability.

METHODS: 

We placed intraoperative Cs-131 brachytherapy in 30 cavities postresection of brain metastases. Seeds-on-a-string were placed like barrel staves within the cavity with fibrin glue. Serial magnetic resonance imaging occurred postoperatively. Preoperative tumor volumes were compared with postoperative cavity volumes to evaluate volume stability. Thirty patients who underwent postresective stereotactic radiosurgery (SRS) were used as a control group for volumetric comparison.

RESULTS: 

Cs-131 and SRS patients exhibited consistent cavity shrinkage over the median 110-day follow-up (P < .001), with total median shrinkage of 56.5% (Cs-131) and 84.8% (SRS). During the first month when ≈88% of Cs-131 dosage is delivered, however, there was nonsignificant volume decrease in the Cs-131 group (median 22.0%; P = .06), whereas SRS patients showed significantly more shrinkage (46.7%; P = .042). No events of radiation necrosis occurred in either group.

CONCLUSION: 

Cs-131 patients exhibited significantly less cavity shrinkage than SRS patients during the first critical month with 88% Cs-131 dose delivery. This significant difference in shrinkage suggests that the intracavitary seeds-on-a-string technique facilitates increased cavity stability, promoting more homogenous dose delivery.

ABBREVIATIONS: 

Cs-131, Cesium-131

FLAIR, fluid-attenuated inversion recovery

I-125, Iodine-125

SRS, stereotactic radiosurgery

WBRT, whole brain radiotherapy