Updated Outcome and Analysis of Tumor Response in Mobile Spine and Sacral Chordoma Treated with Definitive High Dose Photon/Proton Radiotherapy
Menée à partir de données portant sur 40 patients atteints d'un chordome du sacrum ou de la partie mobile de la colonne vertébrale et ayant reçu une protonthérapie ou une radiothérapie par faisceaux de photons (durée médiane de suivi : 50,3 mois), cette étude analyse la réponse tumorale à une haute dose de rayonnements ionisants
Purpose : Treatment of spine and sacral chordoma generally involves surgical resection, usually in conjunction with radiotherapy. In certain circumstances where resection may result in significant neurological or organ dysfunction, patients can be treated definitively with radiotherapy alone. Herein, we report the outcome and the assessment of tumor response to definitive radiotherapy. Materials and Methods : A retrospective analysis was performed on 40 patients with unresected chordoma treated with photon/proton radiotherapy. Nineteen patients had complete sets of imaging scans. Soft tissue and bone compartment of the tumor were defined separately. Tumor response was evaluated per modified RECIST criteria and volumetric analysis. Results : With median follow up of 50.3 months, the five-year local control rate, overall survival, disease specific survival and distant failure rate were 85.4%, 81.9%, 89.4% and 20.2% respectively. Eighty-four CT and MRI scans were reviewed. Among the 19 patients, only four local failures occurred and the median tumor dose was 77.4 GyRBE. Analysis, at a median follow-up of 18 months, showed significant volumetric reduction of the Total Target Volume (TTV) and the Soft Tissue Target Volume (STTV) within the first 24 months after treatment initiation followed by further gradual reduction throughout the rest of the follow up period. The median maximum percent volumetric regression of TTV and STTV were 43.2% and 70.4% respectively. There was only a small reduction in bone target volume over time. In comparison to modified RECIST criteria, volumetric analysis was more reliable, reproducible and could help in measuring minimal changes in the tumor volume. Conclusion : These results continue to support the use of high-dose definitive radiotherapy for selected patients with unresected spine and sacral chordomas. Assessment of tumor response to radiotherapy via volumetric analysis is superior to modified RECIST criteria in chordoma patients. Evaluating the soft tissue target volume is an excellent indicator of tumor response.