Multi-criteria optimization and decision-making in Radiotherapy

Introduction: La radiothérapie est une des branches de l'oncologie dont le but est la destruction des tumeurs tout en préservant les tissus sains . Avant de délivrer la dose au patient, un plan de traitement, spécifique au patient, est créé. Malgré les progrès technologiques, ce plan de traitement reste un compromis entre la protection des tissus sains et une irradiation suffisante de la tumeur. Un plan est appelé Pareto optimal s'il n'existe pas d'autre solution qui améliore au moins un critère sans péjorer un autre. Cette thèse avait pour objectif d'investiguer le processus de prise de décision à critères multiples dans l'incertitude pendant l'évaluation d'un plan de traitement, tout en tenant compte les composants visuels du processus. Matériaux et méthodes : initialement, les patterns d'évaluation visuels de décideurs ont été quantifiés par des techniques d'eye-tracking. Dans la deuxième partie de la thèse, les désaccords entre les plans dosimétriques de navigation basés sur la fluence et les plans finaux délivrés après que la dose soit calculée par le module d'optimisation à critères multiples d'un système de planification commercialisé. Finalement, des fronts Pareto ont été créés manuellement et une région cliniquement intéressante a été identifiée après une évaluation des plans. Résultats : Le processus d'évaluation, parallèlement à l'eye-tracking, a relevé des légères différences dans la qualité perçue des plans et par conséquence des différences dans lé choix des plans de traitement, acceptés ou rejetés. Pour les fronts Pareto automatiques, des désaccords dosimétriques entre les plans navigués et ceux délivrés ont été démontrés. Avec les fronts Pareto manuels, une région dans laquelle les plans Pareto optimaux sont considérés cliniquement équivalents a été identifiée. Discussion-conclusions: Bien qu'il existe un consensus parmi les décideurs sur une région cliniquement significative sur le front Pareto, des différ nces existent encore concernant la qualité perçue d'un plan de traitement. Les différences dosimétriques entre les plans de navigation basés _ sur la fluence et le plan délivrable peuvent encore limiter le bénéfice d'un choix d'un plan optimal en fonction des préférences cliniques. Ces éléments devraient être pris en considération pour la conception de la technologie d'un système d'aide décisionnelle, afin d'intégrer les informations relatives aux préférences cliniques dans ce système ou de utiliser ces informations lors de l'optimisation pour conduire la recherche vers les régions cliniquement préférées. -- Introduction: Radiation therapy is a discipline of oncology that aims at destroying the cancerous tumor while preserving healthy tissues. Before delivering the radiation dose to the patient, a treatment plan, specific to the patient, is created. That treatment plan remains a compromise between healthy tissue sparing and sufficient tumor irradiation, despite the advances in the technology available. Aplanis called "Pareto optimal" if there is no other solution that improves at least one criterion without deteriorating another. This thesis aimed to investigate the multi-criteria decision-making under uncertainty during treatment plan evaluation, while taking into consideration the visual componen_ts of the process. Material and methods: lnitially, the visual evaluation patterns of the decision makers were quantified with eye-tracking techniques. ln the second part of the thesis, dosimetric disagreements between fluence based navigated plans and the resulting deliverable plans after dose calculation in the multi-criteria optimization module of a commercial treatment planning system were evaluated. Finally, manual Pareto fronts were created and after pair plan evaluations a clinically interesting area on the Pareto front was identified. Results: The evaluation process, in parallel with the eye-tracking, revealed slight differences in the perceived quality of the plans and therefore differences in which plans were accepted or rejected. For the automated Pareto fronts, dosimetric disagreements between navigated and deliverable plans were shown. With the manuai Pareto fronts it was· sh own thatthere is an area in which Pareto optimal plans are considered clinically equivalent. Discussion-Conclusions: Although there is a consensus arriong decision makers on a clinically relevant area on the Pareto front, there are still differences concerning the perceived quality of a treatment plan. Dosimetric differences between navigated and deliverable plans may fLirther limit the benefit o( "fine-tuning" and choosing an optimal plan according to clinicat preferences. These elements should be taken into account when decision supp<:>rt technology is designed, in order to integrate information about clinical preferences into a decisiOn'-making support system or use it during optirnization in order to lead the search towards clinically preferred regions

A clinical distance measure for evaluating treatment plan quality difference with Pareto fronts in radiotherapy

We present a clinical distance measure for Pareto front evaluation studies in radiotherapy, which we show strongly correlates (r = 0.74 and 0.90) with clinical plan quality evaluation. For five prostate cases, sub-optimal treatment plans located at a clinical distance value of >0.32 (0.28–0.35) from fronts of Pareto optimal plans, were assessed to be of lower plan quality by our (12) observers (p < .05). In conclusion, the clinical distance measure can be used to determine if the difference between a front and a given plan (or between different fronts) corresponds to a clinically significant plan quality difference

A treatment planning comparison of contemporary photon-based radiation techniques for breast cancer

Background and purpose: Adjuvant radiation therapy (RT) of the whole breast (WB) is still the standard treatment for early breast cancer. A variety of radiation techniques is currently available according to different delivery strategies. This study aims to provide a comparison of six treatment planning strategies commonly adopted for breast-conserving adjuvant RT and to use the Pareto concept in an attempt to assess the degree of plan optimization. Materials and methods: Two groups of six left- and five right-sided cases with different dose prescriptions were involved (22 patients in total). Field-in-Field (FiF), two and four Fields static-IMRT (sIMRT-2f and sIMRT-4f), Volumetric-Modulated-Arc-Therapy (VMAT), Helical Tomotherapy (HT) and Static-Angles Tomotherapy (TomoDirect™ – TD) were planned. Dose volume constraints were taken from the RTOG protocol 1005. Pareto fronts were built for a selected case to evaluate the reliability of the plan optimization process. Results: The best target dose coverage was observed for TD able to improve significantly (p < 0.01) the V95% in a range varying from 1.2% to 7.5% compared to other techniques. The V105% was significantly reduced up to 2% for HT (p < 0.05) although FiF and VMAT produced similar values. For the ipsilateral lung, V5Gy, V10Gy and Dmean were significantly lower than all other techniques (p < 0.02) for TD while the lowest value of V20Gy was observed for HT. The maximum dose to contralateral breast was significantly lowest for TD (p < 0.02) and for FiF (p < 0.05). Minor differences were observed for the heart in left-sided patients. Plans for all tested techniques were found to lie on their respective Pareto fronts. Conclusions: Overall, TD provided significantly better results in terms of target coverage and dose sparing of ipsilateral lung with respect to all other evaluated techniques. It also significantly minimized dose to contralateral breast together with FiF. Pareto front analysis confirmed the reliability of the optimization for a selected case. Keywords: Treatment planning, Whole-breast irradiation, Planning comparison, Pareto fron