Rôle de la tomodensitométrie à double énergie/double source pour la personnalisation des traitements de radiothérapie

Le futur de la radiothérapie réside dans le développement de stratégies visant à adapter les traitements à chaque individu. La tomodensitométrie à double énergie/double source (DECT/DSCT) est une technologie d’imagerie permettant de caractériser avec précision les tissus (sains et tumoraux) et d’imager le cœur en mouvement. En raison de ses fonctionnalités, la technologie du DECT/DSCT a le potentiel de jouer un rôle important dans la personnalisation des traitements de radiothérapie. Nous avons exploré le rôle du DECT/DSCT dans 3 études cliniques prospectives, relatives à la planification des traitements de radiothérapie. Dans une première approche, nous avons évalué le rôle du DECT pour l’évaluation de la fonction du parenchyme pulmonaire en radiothérapie thoracique (conventionnelle et stéréotaxique). Nous avons émis l’hypothèse qu’une quantification précise de la concentration d’iode du parenchyme pulmonaire, dérivée du DECT, permettrait de déterminer les régions pulmonaires les plus fonctionnelles à éviter lors de la planification de la radiothérapie. Nous avons démontré la faisabilité et la validité d’une méthode de quantification de la fonction pulmonaire en utilisant la cartographie d’iode du DECT. De plus, nous avons montré que l’incorporation de cette information en planification de radiothérapie peut réduire significativement la dose aux régions pulmonaires fonctionnelles dans le but de réduire les toxicités. Dans une deuxième approche, nous avons évalué le rôle du l’imagerie à double-source (DSCT) pour une évaluation individualisée du mouvement cardiaque lors de la planification des traitements de radiothérapie. Nous avons montré que le DSCT permettait de visualiser et quantifier le mouvement des sous-structures cardiaques notamment les veines pulmonaires et les artères coronaires, et ainsi déterminer un volume cible personnalisé pour chaque patient. De plus, nous avons montré le bénéfice dosimétrique d’une irradiation du sein gauche avec synchronisation cardiaque (limitée à la phase systolique) pour épargner les sous-structures cardiaques, notamment de l’artère antérieure descendante gauche, une structure critique dans le développement des toxicités cardiaques post-radiques. Finalement, utilisant à nouveau la capacité de quantification précise de la concentration d’iode, nous avons évalué le rôle du DECT pour dériver la perfusion des tumeurs du larynx et de l’hypopharynx traitées par radiothérapie. Dans un contexte exploratoire de 25 patients, nous avons démontré que les statistiques quantitatives dérivées des cartes d’iodes tumorales étaient prédictives du contrôle locorégional chez ces patients, suggérant un rôle de ces cartes d’iode comme bio-marqueurs prédisant l’agressivité tumorale. Les résultats de nos travaux centrés sur ces 3 stratégies démontrent que le DECT/DSCT a le potentiel de jouer un rôle important à divers niveaux dans la personnalisation de la planification des traitements radiothérapie, notamment: 1) pour l’évaluation de la fonction des tissus sains; 2) pour la détermination personnalisée du mouvement cardiaque, et 3) comme outil prédictif du contrôle tumoral.The future of radiotherapy lies in the development of strategies to adapt treatments to each individual. Dual energy / dual source computed tomography (DECT/DSCT) is an imaging technology that allows for accurate tissue characterisation (organs at risk or tumors) and that can capture precisely the anatomy of the heart in motion. DECT/DSCT technology has the potential to be important player in personalized radiotherapy. We explored the role of DECT/DSCT in radiotherapy planning in the context of 3 prospective clinical studies. First, we evaluated the role of DECT imaging for the assessment of lung function in lung cancer radiotherapy planning (both conventionally fractionated and stereotaxic radiotherapy). We hypothesized that accurate quantification of DECT iodine concentration could be used in treatment planning to assesses and preserve functional parenchyma. We demonstrated the feasibility and validity of a novel lung function quantification method using DECT iodine mapping. In addition, we showed that incorporating this information into radiotherapy planning could help improve lung dosimetry, and thus potentially reduce toxicities. In a second approach, we evaluated the role of DSCT for individualized assessment of cardiac motion in radiotherapy planning. We showed that the DSCT allows visualization and quantification of motion of cardiac sub-structures, including the pulmonary veins and coronary arteries, and therefore can be used to determine personalized target volume for each patient. In addition, we quantified the dosimetric impact of cardiac-gated radiotherapy in left breast cancer radiotherapy and demonstrated significant sparing of cardiac sub-structures with this method, in particular sparing of left anterior descending artery, a critical structure involved in radiation-induced cardiovascular toxicities. Finally, we assessed the role of DECT in determining tumor perfusion in larynx/hypopharynx cancers using the iodine concentration quantification method. In an exploratory prospective cohort of 25 patients with cancer of the larynx or hypopharynx, we demonstrated that histogram statistics derived from tumor iodine maps could predict locoregional control in these patients. This finding supports the role of iodine concentration maps as functional biomarkers to predict tumor aggressiveness. The results of our work focused on these various strategies demonstrate that DECT/DSCT has the potential to play an important role in the following 3 avenues of personalized radiotherapy: 1) for the evaluation of functional healthy tissues; 2) for individualized determination of optimal margins or cardiac-gating window in radiotherapy involving the heart and, 3) for prediction of cancer control outcomes

LP++: A Surprisingly Strong Linear Probe for Few-Shot CLIP

In a recent, strongly emergent literature on few-shot CLIP adaptation, Linear Probe (LP) has been often reported as a weak baseline. This has motivated intensive research building convoluted prompt learning or feature adaptation strategies. In this work, we propose and examine from convex-optimization perspectives a generalization of the standard LP baseline, in which the linear classifier weights are learnable functions of the text embedding, with class-wise multipliers blending image and text knowledge. As our objective function depends on two types of variables, i.e., the class visual prototypes and the learnable blending parameters, we propose a computationally efficient block coordinate Majorize-Minimize (MM) descent algorithm. In our full-batch MM optimizer, which we coin LP++, step sizes are implicit, unlike standard gradient descent practices where learning rates are intensively searched over validation sets. By examining the mathematical properties of our loss (e.g., Lipschitz gradient continuity), we build majorizing functions yielding data-driven learning rates and derive approximations of the loss's minima, which provide data-informed initialization of the variables. Our image-language objective function, along with these non-trivial optimization insights and ingredients, yields, surprisingly, highly competitive few-shot CLIP performances. Furthermore, LP++ operates in black-box, relaxes intensive validation searches for the optimization hyper-parameters, and runs orders-of-magnitudes faster than state-of-the-art few-shot CLIP adaptation methods. Our code is available at: \url{https://github.com/FereshteShakeri/FewShot-CLIP-Strong-Baseline.git}

Stereotactic Body Radiotherapy in Recurrent and Oligometastatic Head and Neck Tumours

The treatment of head and neck cancers (HNCs) encompasses a complex paradigm involving a combination of surgery, radiotherapy, and systemic treatment. Locoregional recurrence is a common cause of treatment failure, and few patients are suitable for salvage surgery. Reirradiation with conventional radiation techniques is challenging due to normal tissue tolerance limits and the risk of significant toxicities. Stereotactic body radiotherapy (SBRT) has emerged as a highly conformal modality that offers the potential for cure while limiting the dose to surrounding tissue. There is also growing research that shows that those with oligometastatic disease can benefit from curative intent local ablative therapies such as SBRT. This review will look at published evidence regarding the use of SBRT in locoregional recurrent and oligometastatic HNCs

A randomized phase III trial of stereotactic ablative radiotherapy for patients with up to 10 oligometastases and a synchronous primary tumor (SABR-SYNC): study protocol

BACKGROUND Emerging randomized data, mostly from phase II trials, have suggested that patients with oligometastatic cancers may benefit from ablative treatments such as stereotactic ablative radiotherapy (SABR). However, phase III data testing this paradigm are lacking, and many studies have examined SABR in the setting of metachronous oligometastatic disease. The goal of the SABR-SYNC trial is to assess the effect of SABR in patients with oligometastatic cancers and a synchronous primary tumor. METHODS One hundred and eighty patients will be randomized in a 1:2 ratio between standard of care (SOC) palliative-intent treatments vs. SOC + ablative therapy (SABR preferred) to all sites of known disease. Randomization will be stratified based on histology and number of metastases at enrollment. SABR may be delivered in 1-, 3- and 5-fraction regimens, with recommended doses of 20 Gy, 30 Gy, and 35 Gy, respectively. Non-SABR local modalities (e.g. surgery, thermal ablation, conventional radiation) may be used for treatment of the primary or metastases at the discretion of the treating physicians, if those modalities are clinically preferred. The primary endpoint is overall survival, and secondary endpoints include progression-free survival, time to development of new metastatic lesions, time to initiation of next systemic therapy, quality of life, and toxicity. Translational endpoints include assessment of circulating tumor DNA and immunological predictors of outcomes. DISCUSSION SABR-SYNC will provide phase III data to assess the impact of SABR on overall survival in a population of patients with synchronous oligometastases. The translational component will attempt to identify novel prognostic and predictive biomarkers to aid in clinical decision making. TRIAL REGISTRATION Clinicaltrials.gov NCT05717166 (registration date: Feb. 8, 2023)

Oligometastatic Head and Neck Cancer: Challenges and Perspectives

A minority of patients with metastatic head and neck squamous cell carcinoma (HNSCC) present with oligometastatic disease. Oligometastasis not only reflects a disease state, but might also present an opportunity for cure in the metastatic setting. Radical ablation of all oligometastatic sites may confer prolonged survival and possibly achieve cure in some patients. However, substantial debate remains about whether patients with oligometastatic disease could benefit from curative intent therapy or whether aggressive treatments expose some patients to futile toxicity. Optimal selection of patients, carefully balancing the currently known prognostic factors against the risks of toxicity is critical. Emerging evidence suggests that patients with a limited burden of disease, viral-related pharyngeal cancer, metachronous metastasis and lung-only metastasis may benefit most from this approach. Efforts are underway to identify biomarkers that can detect oligometastasis and better select patients who would derive the maximum benefit from an aggressive radical approach. The combination of radiotherapy and immunotherapy promises to enhance the anti-tumoral immune response and help overcome resistance. However, optimization of management algorithms, including patient selection, radiation dose and sequencing, will be critical in upcoming clinical trials. This review summarizes recent knowledge about the characteristics and investigational efforts regarding oligometastasis in HNSCC