An investigation of correlation-based tumor motion using external surrogates for precise CyberKnife-based SBRT: A prospective study
Mohadeseh Torabi, Ahmad Esmaili Torshabi and Mohammad Ali Bijari
Introduction: The success of precise radiotherapy strongly depends on patient-specific tumor characteristics and motion behavior. This approach is particularly effective for treating tumors located in the thoracic region, where respiratory-induced motion plays a critical role. In this prospective study, we investigated the motion behavior of four moving tumors by analyzing the correlation between tumor motion and external surrogate motion in patients treated with CyberKnife-based stereotactic body radiation therapy (SBRT).
Methods: In this work, a motion database of a large number of patients with lung, liver, pancreas, and abdominal tumors treated with the CyberKnife Synchrony System was utilized. Spearman’s correlation coefficient was used for this data to find the correlation between the tumor and the external markers’ motion.
Results: Based on the average percentage match results obtained from the correlation coefficient parameter, liver tumors with of 57.87% match percentage have the most agreement with external markers. In contrast, lung tumors with 51.12% match percentage have the worst correlation. Additionally, in both tumor types, the z-axis of the markers represents the highest match percentage regarding x- and y-motion directions of external markers.
Conclusion: In the current clinical method using the CyberKnife system, all patients with each type of tumor are treated conventionally using the same strategy and without any sensitivity or consideration of tumor type and its correlation with external markers. The achievements of this work can be helpful in realizing which tumor has in good or bad correlation with external markers. The proposed strategy divides difficult or complicated tumors regarding with easier tumor types to intelligently show a treatment plan with proper model selection, training, and updates during the treatment.
Keywords: external surrogates, radiotherapy, motion behavior, correlation coefficient
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