Improving Clinical Decision-Making in Radiotherapy: A Comparative Analysis of Linear-Quadratic LQ and Linear-Quadratic-Linear LQL Dose Models.

Aims: Radiotherapy is an essential component of cancer treatment, requiring accurate dose planning to optimise tumour control while sparing healthy tissues. This study, originating from a radiobiology workshop held during the 27th Congrès National de Cancérologie et de Radiothérapie-2024 in Sousse, Tunisia, aims to investigate advanced dose modelling approaches, focussing on the linear-quadratic (LQ) and linear-quadratic-linear (LQL) models, to refine the calculation of biologically effective doses (BED) and improve treatment personalisation.

Methods: The workshop brought together experts in the field to discuss and evaluate the latest advancements in dose modelling, providing a comprehensive overview of current best practices and emerging trends. Using tools such as LQL-equiv and other BED calculators, we integrated patient-specific data (eg, fractionation schedules and organ-at-risk (OAR) constraints) to predict outcomes such as normal tissue complication probabilities (NTCPs). Unlike many theoretical studies, our approach embeds these models within a unified interface tailored to real clinical scenarios, enabling practitioners to simulate and adjust treatment plans based on complex, practical constraints.

Results: Through a series of clinical case studies (including treatment interruptions, palliative boosts, and re-irradiation scenarios), participant responses were analysed using the Jaccard similarity index, revealing a significant lack of consensus in treatment planning decisions (mean agreement of 25.83%). This variation illustrates the current ambiguity among clinicians regarding which model to use and how to apply it, despite access to advanced tools. This heterogeneity in decision-making could lead to divergent treatment recommendations for patients with clinically similar profiles.

Conclusion: While the LQ and LQL models offer promising tools for personalised radiotherapy, their interpretation and implementation remain highly variable. In addition, the question of professional responsibility in dose equivalence calculations emerged as a key issue as many departments lack clearly defined accountability frameworks. This study emphasises the need for standardised guidelines, enhanced training programs, and decision support systems to reduce interobserver variability and ensure effective clinical adoption, ultimately improving patient care. The findings underscore the importance of harmonising predictive modelling practices to achieve more consistent and effective radiotherapy outcomes.