Stereotactically guided conformal radiotherapy for meningiomas

Purpose: Stereotactically guided conformal radiotherapy, (SCRT) is a high p recision technique of conformal radiotherapy (RT) which reduces the volume of normal tissue irradiated compared to conventional RT and may lead to a r eduction in long-term toxicity We describe the technique and the preliminar y 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 sku ll (n = 3) meningiomas were treated with SCRT. The technique employed immob ilization in a Gill-Thomas-Cosman (GTC) frame and CT localization with a Br own-Roberts-Wells (BRW) fiducial system for stereotactic space definition. The planning target volume (PTV) was defined as gross tumour volume (GTV) a nd a 0.5-1 cm margin. Treatment was delivered with three (12 patients) or f our noncoplanar conformal fixed fields (12 patients) Conformal blocking was achieved either with lead alloy blocks (n = 11) or with a multi-leaf colli mator (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 o ut 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 en d of radiotherapy, seven of 15 patients with neurological deficit had an im provement 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 overal l survival are 100%, which is within the range expected for conventional fr actionated radiotherapy for meningiomas. Conclusions: SCRT is a feasible technique of high precision conformal RT fo r patients with meningiomas. Potential advantages in tumour control, surviv al and toxicity over conventional RT, require evaluation in long-term prosp ective studies. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.