Connective Tissue Oncology Society

2001 CTOS Annual Meeting Posters— Radiation Oncology

IRRADIATION OF THE DURA INTRA-OPERATIVELY BY CUSTOMIZED 90Y PLAQUES
Herman Day Suit¹, George T.Y. Chen¹, Thomas Mauceri¹, John Monro², Francis J. Hornicek¹, Frank Pedlow¹, Thomas F. DeLaney¹
¹Depts of Radiation Oncology and Orthopaedic Surgery, Massachusetts General Hospital, Harvard Medical School, ²Implant Sciences, Inc.

OBJECTIVE: Objective. A high proportion of tumors of the vertebral bodies which have extended into the vertebral canal impinge on the dura and displace it and in most such instances the cord. The tumor will be in direct contact and have invaded the dura on a microscopic basis. In addition to the intra-canal extension there is accompanying extension into the paravertebral tissues in many of these patients. The residual tumor cells on the dura are judged to be a contributing factor in the high incidence of local failures. External beam techniques do not permit adequate doses to the dura and respecting the tolerance limits of the spinal cord. Hence, the need for dose to be given by high technology procedures directly to the dura as a component of treatment of this category of patients.

METHODS: Methods. Our management strategy is pre-operative radiation in the amount of 50 Gy by intensity modulated X ray or proton beam technique, This results in about approximately 40 Gy to the cord center and marginally higher to the dura. Next, there is resection of the vertebral body [s] and any soft tissue mass. At that point the dura is cleanly exposed but judged to be microscopically positive. A special 90Y foil had been prepared to fit the affected area of the dura. The physical characteristics are: maximum electron energy is 2.3 MeV, dose at 2.5 mm is approximately 20%. The foil is embedded in a plastic applicator with 0.5 mm between foil and the surface, e.g., dura. This system is almost radiation exposure free for the staff. The applicator is applied to the area of concern of the dura. A single dose of 15 Gy requires 10-15 min. Following the intra-operative irradiation, the patient is closed. Post operatively, the treatment is completed. Chemotherapy is administered to patients with high grade large sarcomas.®µ

RESULTS: Results. We have progressed through 3 plaque designs. Four patients have been treated to date; for one, the 90Y foil has been utilized. The other 3 patients were treated by 192Ir plaque or a plaque containing 90Y liquid. This foil is vastly superior to the earlier two models. The applications have been without complications and have required ~25 additional minutes.

CONCLUSION: Conclusions. The 90Y foil system is a technically an easy plaque to utilize and the dose distribution is very attractive for inactivation of tumor cells on the dura.