Purpose: Skull-base chordomas (sbC) are rare bone tumors presenting within the clivus or spinal axis, characterized by significant tissue heterogeneity. Their shapes are variable, likely determined by proximity to surrounding anatomic barriers, making them a typical indication for proton therapy (PT). Here we investigate whether shape and/or textural features of the pre-treatment tumour correlate with clinical outcome.
Methods: We retrospectively analyzed 50 sbC patients treated using PBS-PT at our institute. Pre-PT tumor shape and texture (Tab.1) were evaluated on DWI- and T2w-MRI images using in-house developed software and were classified using clustering algorithms (Kmeans) considering both tumor and organs-at-risk (OARs) features, which were cross-correlated with recurrences.
Results: Fig,1 shows two contrasting tumours. (a) is a case with high sphericity and small surface-area (0,86 and 2409mm^2) which did not recur. In contrast the tumour in (b), with values of 0,27 and 8846mm^2 respectively, did recur. Overall, clustering analysis uniquely identified 4 out of 5 recurrences based on these morphological features. However, due to the small number of recurrences, this result is not statistically significant. Other features, such as compactness and signature-mean were significantly correlated (correlation-coeff.>0.85; Fig.1c) but no correlation was observed between textural features and clinical outcome.
Conclusion: Sphericity and surface-area have been found to be potential predictive factors for treatment outcome in sbC. Greater surface values and protrusions (e.g. Fig.1b) could indicate a larger area of contact between tumor and normal-tissue, thus increasing the probability of tumor infiltration. We are currently extending our analysis to a larger patient cohort.