Meningiomas: genetics, malignancy, and the role of radiation in induction and treatment. The Richard C. Schneider Lecture

The role of postoperative irradiation in the management of sphenoid wing meningiomas. A preliminary report

PURPOSE

To determine whether postoperative radiation therapy decreases recurrence rates in subtotally excised and recurrent sphenoid wing meningiomas.

METHODS

Patients with primary subtotally excised and recurrent sphenoid wing meningiomas who underwent surgery between 1981 and 1994 (n = 105) were prospectively followed for recurrence. Postoperative radiation was not recommended in patients who had complete excision; therefore, their recurrence rates were not evaluated in this study. Patients with malignant meningiomas also were excluded from analysis. Recurrence was defined as evidence of tumor growth on neuroimaging with or without clinical symptoms.

RESULTS

Follow-up information was available for 86 patients; 69 had primary subtotally excised tumors and 17 had recurrent tumors. Follow-up information was unavailable in the remaining 19 patients. Tumor location and histopathology, type of surgery performed, and patient sex and age were similar in the irradiated and nonirradiated subgroups. Postoperative irradiation was delivered to 31 patients with primary tumors and 11 with recurrent tumors; none of these 42 patients had recurrence during a mean observation period of 4.2 and 3.5 years, respectively. The nonirradiated group consisted of 38 patients with primary tumors and 6 with recurrent tumors; 16 of 18 patients who had primary meningiomas had a recurrence and 5 of 6 who had recurrent tumors had another relapse (mean interval between resection and recurrence, 4.4 years and 14 months, respectively).

CONCLUSIONS

Postoperative radiation appeared to delay recurrence in subtotally excised and recurrent sphenoid wing meningiomas during the time frame of this study.

Paediatric meningeal tumours

We review our experience of meningeal tumours in patients under 16 years who were treated between 1957 and 1993. These were 16 with meningiomas (median age 12 years) and 5 with poorly differentiated malignant meningeal tumours (median age 3 years). The incidence of meningeal tumours in this period was 1.62% of all CNS tumours. There were 19 supratentorial tumours (5 intraventricular), 1 tentorial and 1 cervical. Surgical excision was complete in 12 patients and incomplete in 6; in 2 patients a biopsy only was undertaken. The remaining patient had radiological diagnosis only. All 5 patients in the group with malignant poorly differentiated tumours died (median survival 5 months), confirming the aggressive nature of these lesions. Of the 16 patients with meningiomas, 4 died during followup but 11 of the 12 meningioma patients remaining alive had complete resections. There is a strong tendency for paediatric meningeal tumours to have a supratentorial origin and intraventricular location. The female preponderance found in adults is not evident in children. Incomplete surgical excision or focal neurological deficit at presentation was associated with poor outcome.

Frequent type 2 neurofibromatosis gene transcript mutations in sporadic intramedullary spinal cord ependymomas

OBJECTIVE

To further investigate the role of Type 2 neurofibromatosis (NF2) gene transcript mutations in the sporadically occurring counterparts of NF2-associated tumors.

METHODS

Reverse transcription-polymerase chain reaction followed by agarose gel electrophoresis, single strand conformation polymorphism analysis, and automated deoxyribonucleic acid sequence analysis were used to screen for mutations in the NF2 gene transcript in seven unrelated patients with sporadic intramedullary spinal cord ependymomas.

RESULTS

Five of seven intramedullary spinal cord ependymomas harbored detectable mutations. All of these mutations occurred in the region of the transcript that is homologous to known cytoskeletal proteins and resulted in significant truncation of the predicted protein product.

CONCLUSION

Mutations of the NF2 transcript occur in the majority of sporadic intramedullary spinal cord ependymomas. These mutations are frequent in a region of the transcript that is homologous to a family of cytoskeletal proteins, and they probably render the protein product inactive. These results add to the body of knowledge concerning the role of the NF2 gene transcript in tumorigenesis.

Adjuvant combined modality therapy for malignant meningiomas

Malignant meningiomas constitute 10% to 15% of all meningiomas and limited information exists regarding adjuvant treatment of these aggressive primary brain tumors. Fourteen patients (eight men, six women), ranging in age from 28 to 61 years (median 51 years), were prospectively treated for primary malignant meningiomas according to an institutional protocol. All patients underwent surgery (gross-total in four and subtotal resection in 10 patients) followed in 2 to 4 weeks by involved-field radiotherapy (range 59-60 Gy, median dose 60 Gy). Two to 4 weeks after radiotherapy all patients were treated with adjuvant chemotherapy that included cyclophosphamide, adriamycin, and vincristine (CAV). Patients who underwent gross-total resection received three cycles, whereas those with subtotal resection received six cycles of CAV. Four patients required CAV dose reduction due to myelosuppression, and in three patients, myelosuppression prevented administration of the planned course of CAV. Four patients required transfusions (four received red blood cells, three received platelets), and two developed neutropenic fever without bacteriological documentation. Neuroradiographic response included three partial responses and 11 with stable disease. The median time to tumor progression was 4.6 years (range 2.2-7.1 years) and median survival was 5.3 years (range 2.6-7.6 years). The author concludes that combined modality therapy for the treatment of malignant meningiomas is associated with acceptable toxicity and a modest improvement in survival when compared to patients treated with surgery alone.

High-dose radiation-induced meningiomas in elderly

The authors report 2 cases of cerebral meningiomas following high-dose radiotherapy in elderly patients treated for skull basaloma. These two are the first cases over 65 years old cases reported in the literature. The pathological and clinical characteristics of high-dose radio-induced meningiomas are the following: 1) children appear particularly sensitive to the development of this tumor; 2) there is a female patient predominance, in contrast to the male dominance observed in low-dose meningioma, 3) these tumors present a peak frequency in third decade of life; 4) frequently, these tumors are atypical and recur.

Combined molecular genetic studies of chromosome 22q and the neurofibromatosis type 2 gene in central nervous system tumors

Monosomy of chromosome 22 or deletions of 22q have been described in meningiomas and astrocytic tumors, the incidence of which is increased in Type 2 neurofibromatosis. Recently, the gene for neurofibromatosis Type 2 (NF2) has been identified at Chromosome 22q12, and a tumor suppression role has been suggested. Because there have been only a few studies of the NF2 gene on central nervous system tumors other than vestibular schwannomas, we investigated the potential role of NF2 as a tumor suppressor gene in a group of sporadic meningiomas and astrocytomas. Forty-four tumors (26 meningiomas and 18 astrocytic tumors of different grades) were screened for NF2 mutations for the entire 17 exons by the polymerase chain reaction-single-strand conformation polymorphism method. In addition, 37 tumors and their respective constitutional deoxyribonucleic acid were analyzed for loss of heterozygosity of 22q alleles by four polymorphic microsatellite markers. Seven inactivating mutations were found in Exons 4, 5, 6, and 10 in 7 of 26 (27%) meningiomas, but none were found in astrocytic tumors. Altogether, 69% of meningiomas and 20% of astrocytic tumors revealed a loss of heterozygosity of 22q markers. All tumors with NF2 mutations showed concurrent loss of alleles on 22q, thus fulfilling Knudson's criteria for tumor suppressor genes in meningiomas. We conclude that inactivation of the NF2 gene is involved in the pathogenesis of a proportion of meningiomas but not in astrocytic tumors. Because many meningiomas and some astrocytic tumors had allelic loss of 22q but intact NF2, there is a possibility that other tumor suppressor genes exist on 22q and may be involved in the pathogenesis of central nervous system tumors.