Interstitial radiotherapy of 25 parasellar/clival meningiomas and 19 meningiomas in the elderly. Analysis of short-term tolerance and responses.

I-125 seeds were permanently implanted into 25 parasellar-clival meningiomas (median age of patients, 56 y) and 19 globoid meningiomas in the elderly (median age of patients, 77 y) using stereotactic technique and 3-D dose planning. Total dose at the tumour margin was increased during the series from 100 Gy to 150 Gy. The procedure caused no mortality and no serious bleeding, but injury to the III cranial nerve due to puncture occurred in one (4%) of the 25 parasellar-clival meningiomas. In two (4.5%) of the 44 cases the postoperative CT scan showed a misplaced seed, located at the tumour surface. Nonenhancing hypodense rings developed around the seeds ('hot spots') with a median diameter of 10.5 mm at 12 months corresponding to a median initial activity of 8.7 mCi. In general, meningiomas responded by slow reduction in volume. The parasellar-clival meningiomas were followed-up for a median of 19 months (6-32), and so far 4 tumours have shrunk moderately, 13 slightly, and 5 not at all. Pre-operative III, V or VI cranial nerve signs were present in 17 patients and subsided in 8 of them. On the other hand, facial numbness developed or increased in 9 of the 25 patients, indicating that the V nerve is rather sensitive to this type of irradiation. In the 19 meningiomas of the elderly, the median follow-up time was 14 months (5-26). The median relative tumour volume was 46% at 12 months. Accounting for tumour-related deaths only, the actuarial survival rate was 78% at 12 months and 62% at 24 months. In general, brain oedema persisted despite reduction in tumour volume. Stereotactic implantation of I-125 seeds into intracranial meningiomas is relatively safe. Interstitial radiotherapy represents a potential tool in the control of medium-sized intracranial meningiomas with minimal brain oedema, but its long-term impact and untoward effects remain to be followed-up.