Intraoperative dural irradiation by customized 192iridium and 90yttrium brachytherapy plaques.
OBJECTIVE
After vertebral or paravertebral tumor resection, tumor cells may remain on the dura. Because a tumoricidal dose is difficult to achieve using external beam radiotherapy without exceeding the spinal cord tolerance, we developed intraoperative applicators to deliver additional dose to the dura.


METHODS
Eight patients with vertebral or paravertebral tumor underwent conformal external beam radiotherapy, tumor resection, and intraoperative radiotherapy to the dura involved by tumor. At surgery, vertebra, soft tissue, and epidural tumor were resected. A radioactive applicator plaque was placed on the dura to deliver 7.5-15 Gy, and then removed. Vertebral reconstruction and stabilization was completed. Chemotherapy was administered for large, high-grade sarcomas.


RESULTS
We progressed through three plaque designs, initially (192)Ir, subsequently liquid (90)Y, and finally (90)Y foil in a semicylindrical polycarbonate plaque, in the treatment of 8 patients. The low-energy (90)Y beta-emissions provided a more attractive depth dose profile than that achievable with iridium and gave negligible staff radiation exposure. The (90)Y depth dose measured 29% at 2 mm and 9% at 4 mm from the surface of the foil plaque, with acceptable surface dose homogeneity. The average surface dose rate ranged from 18.7 to 47.6 cGy/min for the iridium plaques and 45.2 to 187.5 cGy/min for the (90)Y plaques. The treatments have been without acute or late neurologic complications. The disease of 6 of 8 patients was locally controlled at median potential follow-up of 24 months.


CONCLUSIONS
The (90)Y foil applicator is technically elegant, easy to use, and superior to the earlier models. It has been incorporated into a protocol for spinal tumor treatment.
DeLaney
Thomas F
TF
Department of Radiation Oncology, Massachusetts General Hospital and Harvard Medical School, Boston, MA 02114, USA. tdelaney@partners.org
Chen
George T
GT
Mauceri
Thomas C
TC
Munro
John J
JJ
Hornicek
Francis J
FJ
Pedlow
Francis X
FX
Suit
Herman D
HD
D001918:Brachytherapy / Q000295:instrumentation / Q000379:methods*; D003131:Combined Modality Therapy / Q000295:instrumentation / Q000379:methods; D016503:Drug Delivery Systems / Q000295:instrumentation / Q000379:methods; D004388:Dura Mater; D005500:Follow-Up Studies; D006801:Humans; D007430:Intraoperative Care / Q000295:instrumentation / Q000379:methods; D007496:Iridium Radioisotopes; D008159:Lumbar Vertebrae; D011874:Radiometry / Q000379:methods; D011879:Radiotherapy Dosage; D013120:Spinal Cord Neoplasms / Q000175:diagnosis / Q000532:radiotherapy / Q000601:surgery; D013125:Spinal Neoplasms / Q000175:diagnosis / Q000532:radiotherapy* / Q000601:surgery*; D013904:Thoracic Vertebrae; D016896:Treatment Outcome; D015021:Yttrium Radioisotopes
D007496:Iridium Radioisotopes; D015021:Yttrium Radioisotopes