Gamma knife radiosurgery for residual skull base chordomas.

Objective: The location of chordomas within the base of the skull and cervical junction prevents complete resection from being achieved. Previous series have shown that stereotactic radiosurgery can be used as a treatment for residual chordomas with good overall results. In the present study, we reviewed our experience in using gamma knife surgery (GKS) to treat patients with residual skull base chordomas.

Methods: Thirty-one patients with residual skull base chordomas underwent gamma knife radiosurgery from June 1996 to December 2004. The mean age of patients was 40.2 years (range: 8-70 years). There were 20 male and 11 females. The post-operative tumor volume treated with GKS ranged from 0.47 to 27.6 cm3, with a mean of 11.4+/-7.4 cm3. The mean tumor margin radiation dose was 12.7 Gy (range: 10-16 Gy), and the mean maximum dose was 29.2 Gy (range: 20.8-40 Gy). Twenty-eight patients were available for follow-up reviews, ranging from 6 to 102 months (mean: 30.2 months) and from 6 to 78 months (mean: 28 months), for clinical and image assessments, respectively.

Results: Kaplan-Meier survival analysis showed a survival of 90.9 and 75.8% after 3 and 5 years, respectively. Most tumors were smaller in size 1 year after treatment, which paralleled an alleviation of clinical symptoms. However, nine chordomas progressed, and seven recurred over the course of follow-up. The actuarial tumor control rate was 64.2 and 21.4% after 3 and 5 years, respectively. No serious radiation-related complication was found in any of the patients with GKS alone.

Conclusions: Gamma knife radiosurgery can be effectively used for residual chordomas beside surgical resection with efficacious tumor control rates.