Interstitial implant radiosurgery for cerebral metastases.

The effectiveness of interstitial implant radiosurgery (IRS) as an alternative or adjuvant treatment to radiotherapy (WBRT) or surgery of cerebral metastases remains unclear. In a retrospective study (1982-1991) we analysed four therapeutic regimes after stereotactic biopsy: IRS with a tumour dose of 60 Gy in combination with WBRT (40 Gy/5 x 2 Gy/week--38 patients), IRS only (tumour dose 60 Gy--22 patients), WBRT only (40 Gy/5 x 2 Gy/week--49 patients), and IRS only for recurrent cerebral metastases (tumour dose 60 Gy--21 patients). Low-activity iodine-125 seeds were used exclusively. IRS was performed in the case of circumscribed, mostly solitary metastases < or = 4 cm in diameter. Patients undergoing combined treatment had the best survival, with a median survival time of 17 months in comparison with 12 months after IRS alone and 7.7 months after WBRT. The median survival of patients with recurrent metastases after IRS was 6 months. A comparison of treatments in the multivariate analysis showed that IRS + WBRT was not superior to IRS alone. The metastases could be locally controlled in every case. There were no radionecroses requiring treatment. Most favourable determinants after IRS or IRS + WBRT were a solitary metastasis and a long time interval between diagnosis of the primary and diagnosis of the cerebral metastases. Our results demonstrate the effectiveness of IRS. For a single cerebral metastasis, IRS as a minimally invasive method offers major advantages.