[Fractionated stereotactic radiotherapy: results in hypophyseal adenomas, acoustic neurinomas, and meningiomas of the cavernous sinus].

PURPOSE

In order to optimize cerebral benign tumor irradiation, fractionated stereotactic radiotherapy allows a focused-volume irradiation (2.1 cm3, 16 mm diameter) under standard fractionation conditions. Results of a retrospective and multicentric analysis are presented.

PATIENTS AND METHODS

Fractionated stereotactic radiotherapy uses the ballistic principles of the radiosurgery: stereotactic localization, multi-beam irradiation, secondary collimation, three-dimensional dosimetry. Standard fractionation is possible with a re-locatable non-invasive stereotactic device. The technique has been used for treating pituitary adenomas (86 patients), acoustic neuromas (32 patients) and cavernous meningiomas (26 patients).

RESULTS

1. pituitary adenomas: cumulative tumoral objective-response rates (42 patients) were respectively 42%, 69% and 88% at 24, 48 and 60 months. The cumulative endocrinologic objective-response rates (32 patients) were respectively 53%, 75% and 85% at 24, 48 and 60 months. The cumulative risk of radio-induced hormonal deficiency varied from 18% (growth hormone [GH]) to 42% for TSH (thyroid stimulating hormone) at 48 months. No other complication was observed; 2) acoustic neuromas: 33 tumors, < 25 mm in diameter, were treated in 32 patients. Tumor control was observed in 29/33 tumors: 14 were stable, 15 decreased and three progressed. Useful hearing was maintained in 9/10 patients. Only three patients (9%) presented persistent complications; 3) cavernous meningioma: 17/19 clinical responses were noted, 20 tumoral stabilisations, one partial response and one progression (22 magnetic resonance imaging [MRI] evaluable patients). One unilateral radio-induced blindness was observed.

CONCLUSION

For these benign tumors, the focused target volume obtained by the fractionated stereotactic radiotherapy seems to be better adapted to the treatment of limited benign tumors than standard radiotherapy. The use of standard fractionation reduces the risk of severe normal tissue damage, sometimes observed for radiosurgery and inherent in the use of single fraction.