Adjuvant versus Boost Stereotactic Radiosurgery for the Management of Adult Skull Base Chordomas: An International Multicenter Study

Introduction: Stereotactic radiosurgery (SRS) has been utilized in managing skull base chordomas (SBC) with good efficacy and safety. The goal of this study was to compare the outcomes of postoperative adjuvant SRS alone (SRS group) versus boost SRS following adjuvant postoperative fractionated radiation therapy (FRT+SRS group) for histologically confirmed SBC in adults.

Methods: Patient data were collected from 10 institutions affiliated with the International Radiosurgery Research Foundation. Overall survival, tumor control, and freedom from any additional treatment (FFAT) were analyzed.

Results: The SRS group and FRT+SRS group encompass 57 (77%) and 17 (23%) patients, respectively. The median radiological follow-up time was 48 months (IQR, 24-85) in the SRS group and 36 months (IQR, 25-41) in the FRT+SRS group. The groups were comparable regarding mean patient age (SRS: 43.2±16.3 years vs. FRT+SRS: 47.4±12.9 years; p=0.34), male sex rates (SRS: N=35 [61.4%] vs. FRT+SRS: N=11 [64.7%]; p=0.78), and mean Karnofsky Performance Status score at SRS (SRS: 88.6±9.5 vs. FRT+SRS: 87±4.7; p=0.52). Among the FRT+SRS group, the fractionated radiation therapy was linear accelerator in 11 patients and proton radiation in 6. During the study period, 8 SRS and 2 FRT+SRS patients died (p=0.80). The groups had comparable 10-year overall survival rates (SRS: 76% vs. FRT+SRS: 80%; p=0.75) and tumor control rates (SRS: 34% vs. FRT+SRS: 45%; p=0.29). However, the SRS group had a superior 10-year FFAT rate (40%) compared to the FRT+SRS group (23%; p=0.02). This finding persisted in the multivariate analysis of the Cox proportional hazards showing a 2.40-fold increase in the relative risk of requiring additional treatment among the FRT+SRS group compared to the SRS group (p=0.04).

Conclusion : In this multicenter study of patients with histologically confirmed SBCs, postoperative adjuvant FRT with subsequent boost SRS did not provide superior overall survival or tumor control rates compared to patients who underwent adjuvant SRS alone.