Abstract
BACKGROUND
The incidence of brain metastasis is approximately 200,000 worldwide annually. Stereotactic radiation therapy of post-operative cavity reduces local recurrence. Surgical cavity size changes significantly with 96.5% demonstrating volumetric change during post-operative period. We sought to define the optimal time interval that preserved the volumetric dimensions between the post-surgical MRI and the CT simulation used for stereotactic radiosurgery planning.
METHODS
Seven patients with brain metastasis that underwent surgical resection and stereotactic radiation treatment at Albany Medical Center from February 2019 to April 2020 were included in the study. A total of 8 target lesions were included. Brain lab planning system was used for contouring the target volume. A postoperative MRI within 24-48 hours after surgery was obtained. 3 patients required an additional interim MRI 16-50 days after surgery. The planning CT simulation was performed 2 days prior and up to 15 days after the post-operative/interim MRI and target volumes were compared.
RESULTS
The average volume of the post-surgical cavity contoured by the neurosurgeons on the post-operative/interim MRI was 15.96 cc (± 7.79 cc, range of 6.54 -24.9 cc). The average volume of the post-surgical cavity contoured by the radiation oncologists on the planning CT was 15.71 (± 7.49 cc, range of 6.53 -24.31 cc). There was no noticeable change in volume size between post-operative/interim MRI and planning CT up to the period of 15 days.
LIMITATION
This was a retrospective pilot study with a small sample size and patients recruited from a single center.
CONCLUSION
There is no change in size of the cavity volume for up to 15 days between post-operative/interim MRI and planning CT. This knowledge will help understand the optimal time interval between post-operative MRI and CT simulation for the stereotactic radiation therapy planning.
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