THE RELATIONSHIP BETWEEN THE TECHNICAL ACCURACY OF STEREOTAXIC INTERSTITIAL IMPLANTATION FOR HIGH-GRADE GLIOMAS AND THE PATTERN OF TUMOR RECURRENCE

Purpose: To correlate the pattern of failure and subsequent survival w ith the technical accuracy of stereotactic brain tumor implantation. M ethods and Materials: The patterns of failure of 47 consecutive patien ts with primary or recurrent gliomas after stereotactic implantation d elivering 60 Gy via removable high activity I-125 sources were reviewe d. When the tumor was covered at all levels by the chosen isodose dist ribution, the implant was considered to be ''ideal.'' If the coverage was not complete, a numerical description of the volume of tumor outsi de the isodose was assigned. Criteria for ''adequate'' and ''inadequat e'' implants were defined. Standard radiographic criteria, with pathol ogic confirmation in 26 cases, were used to categorize the patterns of failure into the following components: central, peripheral, distant ( within the brain parenchyma), leptomeningeal, and spinal. A peripheral failure was scored as being in the ''direction of error'' when the pr escribed isodose did not cover the tumor volume and the subsequent tum or progression was in this region. Survival was calculated from the da te of implantation. Results: Of 47 cases examined, 72% had an element of central and/or peripheral failure and 23% had a component of distan t or meningeal failure. Among the patients with ''adequate'' or ''inad equate'' (''nonideal'') implants who had a component of peripheral fai lure, only 19% were in the ''direction of error. All patients with tec hnically ''inadequate'' implants progressed in both the central and pe ripheral region. Among the groups who had ''ideal,'' ''adequate,'' and ''inadequate'' implants; 37%, 70%, and 75%, respectively, underwent r eoperation [p = not significant (NS)]. Patients who underwent reoperat ion had a longer median survival than those who did not; 521 days vs. 298 days, respectively (p = 0.035). For patients with ''nonideal'' imp lants, a median survival of 470 days was found for patients undergoing reoperation vs. 184 days for those who did not (p = 0.016). Conclusio ns: (a) Patients with ''inadequate'' implants failed in both the centr al and peripheral region in all cases. This pattern, while less common in those with ''ideal'' or ''adequate'' implants, occurred in the maj ority of cases. (b) The technical excellence of the implant had no imp act on survival. (c) Patients with ''nonideal'' implants were more lik ely to have reoperation than those with ''ideal'' implants, and this i ntervention was associated with a significant survival advantage.