A systematic review of the dosimetric consequences of the interplay effect

Purpose: The presence of intrafraction motion introduces challenges to thoracic irradiation. The objective of this review is to evaluate the impact of intra-fraction motion on target dose in lung cancer (interplay effect). 

Method: A comprehensive search was conducted in 2024 across three databases using predefined keywords related to the interplay effect in conjunction with lung cancer. Inclusion criteria encompassed studies involving all external beam radiotherapy modalities, conducted from 2013 onwards. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines were followed. 

Results: Forty-three journal articles were identified meeting the criteria for inclusion in this analysis. The impact of the interplay effect was found to cause discrepancies in the delivered dose distribution to the target structure and organs at risk. The interplay dose discrepancies were quantified using simulation-based and measurement-based approaches in phantoms and retrospectively in patients. Further analysis revealed associations between interplay dose deviation and various breathing features, and beam delivery features. These findings underscore the multifactorial nature of interplay dose deviation, highlighting the need for comprehensive evaluation and consideration of various patient-specific and treatment-related factors in treatment planning and delivery. 

Discussion: This systematic review emphasises the significance of personalised assessment and treatment optimisation strategies. Acquiring parameters during clinical trials for secondary analysis can allow technical features to be correlated with patient outcomes, enhancing our understanding of interplay dose error. Developing sophisticated simulation-based tools that incorporate all patient and machine-related factors will ensure dosimetric accuracy and improve patient outcomes.