Volumetric follow up of brain metastases: a useful method to evaluate treatment outcome and predict survival after Gamma Knife surgery?

OBJECT

Brain metastases are diagnosed in 20 to 40% of all cancer patients and are associated with a considerable drop in life expectancy and often also in quality of life for these patients. Several treatment options are available including surgery, chemotherapy, whole-brain radiotherapy, stereotactic radiotherapy, stereotactic radiosurgery, and Gamma Knife surgery (GKS). However, management of brain metastases still presents a challenge and there is no general consensus on the best treatment strategy. The aim of the authors' study was to further evaluate the efficacy of GKS in the treatment of brain metastases and to evaluate the predictive value of volumetric tumor follow-up measurement.

METHODS

Consecutive patients with controlled systemic cancer and variable numbers of brain metastases were included in this prospective study. Patients with severe symptoms of brain compression underwent surgery before GKS. Each follow-up examination included a thorough neurological examination and a neuroradiological quantitative volumetric tumor analysis. A total of 300 consecutive patients (mean age 58 years) with 703 brain metastases were treated between December 1998 and October 2005. The mean total tumor volume (TTV) was 2.1 cm3. The overall local tumor control rate was 84.5%. In 79% of all treated metastases a mean TTV reduction of 84.7% was achieved using a mean prescription dose of 21.8 Gy. Only few, mostly mild, side effects were observed during the mean follow-up period of 12.7 months. The overall mean progression-free survival period was 9.4 months. There was a statistically significant difference in survival of patients with one compared with multiple metastases, regardless of the histological type and preceding treatment.

CONCLUSIONS

Gamma Knife surgery is a safe and effective treatment for patients with brain metastases regardless of the history of treatment and histological tumor type. It achieves excellent tumor control, significant TTV reduction without causing severe side effects, and accordingly, preserves quality of live. Volume changes after GKS did not serve as a predictor for treatment outcome and survival.