The burden of skull base chordomas: insights from a meta-analysis of observational studies

OBJECTIVE The aim of this study was to provide a quantitative synthesis of the survival outcomes for patients with skull base chordomas, focusing on the role of 1) the extent of resection (gross-total [GTR] vs non-GTR), 2) the type of surgery (primary vs revision), 3) tumor histology, and 4) the different use of adjuvant therapies (proton beam radiotherapy [PBRT], photon radiotherapy [RT], or none). METHODS A systematic review with a meta-analysis was conducted following the 2020 PRISMA guidelines. Observational studies describing adult and pediatric patient cohorts harboring skull base chordomas were included. The primary outcome measures were represented by the 5-year overall survival (OS) and progression-free survival (PFS) rates. The main intervention effects were represented by the extent of resection (GTR vs non-GTR), type of surgical excision (primary vs revision surgeries), tumor histology, and the different use of adjuvant therapies (PBRT, RT, or none). The pooled estimates were calculated using random forest models. The risk of bias was evaluated using the Joanna Briggs Institute checklist for case series. RESULTS Six hundred forty-four studies were identified through a database and register search. After study selection, 51 studies and 3871 patients were included in the meta-analysis. The overall 5-year OS rate was 73%, which increased to 84% among patients undergoing GTR. The overall 5-year PFS rate was 52%, increasing to 74% for patients receiving GTR. The 5-year OS and PFS rates for patients undergoing PBRT were 86% and 71%, compared with 71% and 54% for patients receiving RT, and 55% and 25% when no adjuvant treatments were used. Patients undergoing their first surgery had 2.13-fold greater chances of being disease-free and 1.4-fold greater chances of being alive at 5 years follow-up compared with patients who received a revision surgery. Patients harboring chondroid chordomas had 1.13- and 1.9-fold greater chances of being alive at 5 years compared with patients with conventional and de-differentiated chordomas, respectively. The overall risk of bias was low in the included studies. CONCLUSIONS The results of this comprehensive meta-analysis highlight the tremendous impact of GTR and adjuvant PBRT on improving OS and PFS of patients harboring skull base chordomas, with better survival rates demonstrated for patients with chondroid tumors. Even in experienced hands, the rate of surgical morbidity remains high. Proper management in high-volume centers is mandatory to reach the expected resection goal at the first surgical attempt and to reduce surgical morbidity. The introduction of the endoscopic endonasal approach was related to improved surgical and functional outcomes.