The purpose of this retrospective study was to assess patient survival, tumor control, the risk of complications, and selected variables that predict outcome in chordoma patients who underwent Gamma Knife stereotactic radiosurgery (SRS) as primary or adjuvant management.

     Six participating centers of the North American Gamma Knife Consortium (NAGKC) identified 71 patients who underwent SRS for chordoma between 1988 and 2008. The median patient age was 45 years (range, 7-80 years). The median duration of neurological symptoms and signs before SRS was 6 months (range, 0.1-24 years). Forty-eight patients had prior surgical resections and 20 had prior fractionated radiation therapy.

     The median SRS target volume was 7.1cc (range, 0.9 -109cc) and median margin dose was 15.0 Gy (range, 9- 25 Gy).

     With median follow-up of 5 years after SRS (range, 0.3- 14 years), 23 patients died due to tumor progression. The median overall survival after SRS was 8.7 years. The overall survival after SRS was 93%. Younger age (< 45 years), longer interval between initial diagnosis and SRS (> 3years), no prior RT, no or single prior cranial nerve deficit, and smaller total tumor volume (< 7 cc) were significantly (p<0.05) associated with longer patient survival. Local tumor progression was seen in 23 tumors (32%). Th. Older age (> 45 years), prior RT and larger tumor volume (> 7 cc) were significantly associated with poor tumor control. Fifteen patients underwent additional surgical resection, four had RT, and two had repeat SRS for the management of local tumor progression after SRS.

     This is a retrospective study.

     Stereotactic radiosurgery is a valuable management option for patients with residual or recurrent chordomas.

     With outcomes equivalent or superior to those reported after fractionated proton radiation.