Hypofractionated stereotactic radiotherapy for brain metastases

Purpose: To evaluate efficacy and toxicity of hypofractionated stereotactic radiotherapy (hfSRT) with three different dose concepts for irresectable brain metastases not amenable to radiosurgery (SRS) using non-invasive fixation of the skull. Patients and Methods: From 6/2000 to 6/2005, 150 patients with 228 brain metastases were treated at the dedicated stereotactic radiosurgery system Novalis (TM) (BrainLAB, Feldkirchen, Germany) in two German treatment centers. Three different dose concepts were applied: 5 x 6-7 Gy (A: 72 brain metastases), 10 x 4 Gy (B: 59 brain metastases) and 7 x 5 Gy (C: 97 brain metastases). Median planning target volume (PTV) was 6.1 cm(3) (range, 0.02-95.97). Results: Rates of complete remission (CR), partial remission (PR), no change (NC) and progressive disease (PD) were 42%, 30%, 21% and 7%, respectively (median follow-up 28 months). Median survival was 16 months. Survival at 6 and 12 months was 83% and 66%, respectively. Side effects were dependent on the PTV and on dose concept (median PTV in case of increasing edema or necrosis: 17 cm3, A: 22%, C: 7%). HfSRT with 10 x 4 Gy (B) was well tolerated without side effects. Conclusion: Hypofractionated stereotactic radiotherapy is an effective and safe treatment. In case of brain metastases > 15 cm(3) (diameter > 3 cm) and concerning toxicity, 10 x 4 Gy seem to be more advantageous than shorter fractionation with higher doses while 5 x 6-7 Gy and 7 x 5 Gy were followed by higher response rates. Further specification of tolerance doses and tolerance according to the different brain regions has to be done.