Critical appraisal of experimental radiation modalities for malignant astrocytomas

Survival benefit of stereotactic radiosurgery for patients with malignant glial neoplasms

OBJECTIVE

During an 8-year interval, we evaluated the survival benefit of stereotactic radiosurgery performed in 64 patients with glioblastomas multiforme (GBM) and 43 patients with anaplastic astrocytomas (AA).

METHODS

Adjuvant radiosurgery was performed either before disease progression or for recurrent tumor at the time of disease progression. Clinical and imaging follow-up data were obtained for all patients. The diagnosis of GBM was obtained by performing craniotomies in 41 patients and by performing stereotactic biopsies in 23. The diagnosis of AA was obtained by performing craniotomies in 19 patients (44%) and by performing biopsies in 24.

RESULTS

Of the entire series, the median survival time after initial diagnosis for patients with GBM was 26 months (standard deviation [SD], 19 mo; range, 5-79 mo) and the median survival time after radiosurgery was 16 months (SD, 16 mo; range, 1-74 mo). The 2-year survival rate was 51%. No survival benefit was identified for patients who underwent intravenously administered chemotherapy in addition to radiosurgery (P = 0.97). After undergoing radiosurgery, 12 patients (19%) underwent craniotomies and resections and 4 (6%) underwent subsequent radiosurgery for regional or remote recurrence. For 45 patients who underwent radiosurgery as part of the initial management plan, the median survival time after diagnosis was 20 months. Of the entire series, the median survival time after diagnosis for patients with anaplastic astrocytomas was 32 months (SD, 23 mo; range 5-96 mo) and the median survival time after radiosurgery was 21 months (SD, 18 mo; range 3-93 mo). The 2-year survival rate was 67%. Ten patients (23%) underwent subsequent craniotomies at a mean of 8 months after initial surgery, and two underwent subsequent radiosurgery. There was no acute neurological morbidity after radiosurgery. Histologically proven radiation necrosis occurred in one patient with GBM (1.6%) and two patients with AA (4.7%). For 21 patients for whom radiosurgery was part of the initial management plan, the median survival time after diagnosis was 56 months.

CONCLUSION

In comparison to historical controls, improved survival benefit after radiosurgery was identified for patients with GBM and patients with AA. Although this survival benefit may be related to our selection of patients for radiosurgery based on their having smaller tumor volumes, no selection was made based on location. We observed that radiosurgery was safe and well tolerated. Its effectiveness as an adjuvant therapy deserves a properly stratified randomized trial.

Stereotactic radiosurgery for glioblastoma: a final report of 31 patients

From February 1989 to December 1992, 31 patients who presented with an initial pathological diagnosis of glioblastoma multiforme underwent tumor debulking or biopsy, stereotactic radiosurgery, and standard radiation therapy as part of their primary treatment. Presenting characteristics in the 22 men and nine women included a median age of 57 years, Karnofsky Performance Scale score median of 80, and median tumor volume of 16.4 cm3. Stereotactic radiosurgery delivered a central dose of 15 to 35 Gy with the isocenter location, collimator size, and beam paths individualized by means of three-dimensional software developed at the University of Wisconsin. The peripheral isodose line varied from 40% to 90% with a median of 72.5% and a mode of 80%. The mean follow-up period was 12.84 months with a median of 9.5 months. Statistical analysis was performed using Kaplan-Meier analysis and log-rank comparison of risk factor groups. The parameters of age, initial Karnofsky Performance Scale score, and biopsy were significantly different in patient survival from debulking; but no difference was noted between single and multiple isocenters and patterns of steroid requirement. Radiographic recurrences were divided by location into the following categories: central (within central stereotactic radiosurgery dose), 0; peripheral (within 2 cm of central dose), 19; and distant (> 2 cm), 4. There is no evidence of recurrence in five surviving patients. Actuarial 12-month survival was 37%, with a median survival of 9.5 months. These values are similar to previous results for surgery and standard radiotherapy alone. The results suggest that the curative value of radiosurgery is significantly limited by peripheral recurrences.