Dose-response relationships for radiotherapy of brain metastases - Role ofintermediate-dose stereotactic radiosurgery plus whole-brain radiotherapy

The effects of intermediate-dose radiotherapy consisting of whole-brain rad iotherapy (WBRT, 10 fractions of 3 Gy) plus stereotactic radiosurgery (SRS) were studied prospectively. Twenty-five adult patients with 31 brain metas tases received WBRT plus linear accelerator (LINAC)-based single dose SRS w ith fixed treatment parameters (10 Gy at the isocenter, target Volume enclo sed by the 90% isodose). Median age was 63 years. median Karnofsky performa nce status 80%, and median diameter of brain metastases 2.4 cm. Fifteen pat ients had non-small-cell lung cancer. Because of some early deaths, only 26 lesions could be evaluated for response. We observed 1 complete and 15 par tial remissions. Median time to progression inside or outside the SRS Volum e was 4.5 months. Actuarial local control of SRS-treated lesions was 61% at I year. At that time, only 37% of patients were free from new lesions outs ide the SRS volume. Median survival and cause-specific survival were 2.3 an d 4.5 months, respectively (I-year survival rate 8% and 21%). Ten patients died of progressive brain metastases, 13 from extracranial disease progress ion (unknown cause of death in 2 cases). Comparable to SRS studies with hig her doses, the majority of brain failures occurred outside the SRS volume a nd more patients died of extracranial progression than of uncontrolled brai n metastases. Failure to improve survival can be explained by the high perc entage of patients with extracranial metastases (52%). However, the present results appear less favorable than those of previous studies of SRS with 1 5 Gy to 16 Gy (1-year actuarial local control rates of 66-89%). Therefore, we recommend SRS with 15 Gy to 16 Gy for patients whose favorable prognosti c factors justify a boost after WBRT.