Gamma knife surgery efficacy in controlling postoperative residual clival chordoma growth

Objective: This study primarily aims to evaluate the efficacy of gamma knife surgery in controlling growth progression rate of residual clival chordoma through retrospective outcome analysis of 12 consecutive patients. Patients and methods: Data for 12 consecutive patients underwent GKS for post-operative residual histologically verified clival chordoma at our institution (IMC - Cairo- Egypt) from 2006 through end of 2017 were retrospectively reviewed and analyzed with mean follow-up period of 45 months (range12-120 months). Results: In the last follow up MR, tumor growth control was achieved in 33.3% of patients (mean treated tumors volume was 2.7cc with mean peripheral prescription dose of 16 Gy), and 66.7% of patients reported lost tumor growth control (mean treated tumor volume was 9.2 cc with mean peripheral dose was 13.5 Gy). The overall tumor free progression with mean follow up period of 45mos was 33.3%. The Actuarial 2, 3 and 5 year tumor control rates after initial GKS was 35%, 30% and 25% respectively. Conclusion: Without satisfactory maximum tumor reduction and sufficient high peripheral prescription radiation tumor dose, it should not be expected that GKS could efficiently control the progression of residual clival chordoma, especially for long term.