Stereotactically guided conformal radiotherapy for meningiomas

Purpose: Stereotactically guided conformal radiotherapy, (SCRT) is a high precision technique of conformal radiotherapy (RT) which reduces the volume of normal tissue irradiated compared to conventional RT and may lead to a reduction in long-term toxicity We describe the technique and the preliminary results in patients with inoperable, residual or recurrent meningiomas. Material and methods: From July 1993 to November 1997, 24 patients (median age: 56 years, range: 28-72) with base of skull (n = 21), fair or upper skull (n = 3) meningiomas were treated with SCRT. The technique employed immobilization in a Gill-Thomas-Cosman (GTC) frame and CT localization with a Brown-Roberts-Wells (BRW) fiducial system for stereotactic space definition. The planning target volume (PTV) was defined as gross tumour volume (GTV) and a 0.5-1 cm margin. Treatment was delivered with three (12 patients) or four noncoplanar conformal fixed fields (12 patients) Conformal blocking was achieved either with lead alloy blocks (n = 11) or with a multi-leaf collimator (MLC) (n = 13). Patients were treated on a 6 MV linear accelerator to doses of 50-55 Gy, in 30-33 daily fractions. The treatments were carried out as part of a routine work of a busy radiotherapy department. Results: Median GTV for 24 meningiomas was 21.7 cm(3) (range: 4.4-1.83 cm(3)), SCRT was well tolerated with minimal toxicity Three months after the end of radiotherapy, seven of 15 patients with neurological deficit had an improvement and eight remained unchanged. Two patients experienced early side effects (one VII nerve palsy, one Addisonian state). At a median follow-up of 13-months (range: 3-43) the 1 year progression free survival and overall survival are 100%, which is within the range expected for conventional fractionated radiotherapy for meningiomas. Conclusions: SCRT is a feasible technique of high precision conformal RT for patients with meningiomas. Potential advantages in tumour control, survival and toxicity over conventional RT, require evaluation in long-term prospective studies. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.