Predicting the need for a replan in oropharyngeal cancer: A radiomic, clinical, and dosimetric model.

BACKGROUND: Patients with oropharyngeal cancer (OPC) treated with chemoradiation can experience weight loss and tumor shrinkage, altering the prescribed treatment. Treatment replanning ensures patients do not receive excessive doses to normal tissue. However, it is a time- and resource-intensive process, as it takes 1 to 2 weeks to acquire a new treatment plan, and during this time, overtreatment of normal tissues could lead to increased toxicities. Currently, there are limited prognostic factors to determine which patients will require a replan. There remains an unmet need for predictive models to assist in identifying patients who could benefit from the knowledge of a replan prior to treatment. PURPOSE: We aimed to develop and evaluate a CT-based radiomic model, integrating clinical and dosimetric information, to predict the need for a replan prior to treatment. METHODS: A dataset of patients (n = 315) with OPC treated with chemoradiation was used for this study. The dataset was split into independent training (n = 220) and testing (n = 95) datasets. Tumor volumes and organs at risk (OARs) were contoured on planning CT images. PyRadiomics was used to compute radiomic image features (n = 1218) on the original and filtered images from each of the primary tumor, nodal volumes, and ipsilateral and contralateral parotid glands. Nine clinical features and nine dose features extracted from the OARs were collected and those significantly (p < 0.05) associated with the need for a replan in the training dataset were used in a baseline model. Random forest feature selection was applied to select the optimal radiomic features to predict replanning. Logistic regression, Naïve Bayes, support vector machine, and random forest classifiers were built using the non-correlated selected radiomic, clinical, and dose features on the training dataset and performance was assessed in the testing dataset. The area under the curve (AUC) was used to assess the prognostic value. RESULTS: A total of 78 patients (25%) required a replan. Smoking status, nodal stage, base of tongue subsite, and larynx mean dose were found to be significantly associated with the need for a replan in the training dataset and incorporated into the baseline model, as well as into the combined models. Five predictive radiomic features were selected (one nodal volume, one primary tumor, two ipsilateral and one contralateral parotid gland). The baseline model comprised of clinical and dose features alone achieved an AUC of 0.66 [95% CI: 0.51-0.79] in the testing dataset. The random forest classifier was the top-performing radiomics model and achieved an AUC of 0.82 [0.75-0.89] in the training dataset and an AUC of 0.78 [0.68-0.87] in the testing dataset, which significantly outperformed the baseline model (p = 0.023, testing dataset). CONCLUSIONS: This is the first study to use radiomics from the primary tumor, nodal volumes, and parotid glands for the prediction of replanning for patients with OPC. Radiomic features augmented clinical and dose features for predicting the need for a replan in our testing dataset. Once validated, this model has the potential to assist physicians in identifying patients that may benefit from a replan, allowing for better resource allocation and reduced toxicities.

Evaluation of the correlation between dosimetric, geometric, and technical parameters of radiosurgery planning for multiple brain metastases.

PURPOSE: To evaluate the correlation between dosimetric, geometric, and technical parameters for radiosurgery planning of multiple brain metastasis treatments treated with a linear accelerator with volumetric modulated arc therapy (VMAT) technique. MATERIALS AND METHODS: Data were collected retrospectively from 55 patients who underwent radiosurgery in a single institution from August 2017 to February 2020. Patients presented 4-21 brain metastases were treated with a single fraction with doses between 18 and 20 Gy. Dosimetric variables were collected including V5Gy, V8Gy, V10Gy, V12Gy, V14Gy, conformity index (CI), heterogeneity index (HI), maximum dose (Dmax), and the CI_R50. Geometric variables including the number of lesions, target volumes, the smallest target volume, the largest target volume, and the distance between the isocenter and the most distant lesion (DIL) and technical variables such as the numbers of total arcs, noncoplanar arcs, and isocenters were collected for analysis. RESULTS: The number of lesions had a moderate positive correlation with V5Gy, V8Gy, V10Gy, V12Gy, V14Gy, HI, Dmax, and with the number of total arcs. The target volumes had a positive medium-high correlation with V5Gy, V8Gy, V10Gy, V12Gy, V14Gy, and moderate positive correlation with HI, Dmax, number of arcs and noncoplanar arcs. The CI and CI_R50 had a negative correlation with all volumes related to the target: the target volumes, the smallest, and the largest lesion. A positive correlation was observed between the distance of the isocenter and the most DIL with V5Gy, V8Gy, V10Gy, V12Gy, V14Gy, HI, Dmax, and the number of isocenters. CONCLUSION: It was found that the number of lesions and the target volumes are good predictors of dosimetric indexes of plan evaluation and that the distance between the isocenter and the most DIL harms them.

Dosimetric comparison and assessment of second cancer risk between helical tomotherapy and intensity-modulated radiotherapy in children with craniospinal irradiation / 中华放射肿瘤学杂志

Objective To investigate the dosimetric characteristics between helical tomotherapy ( HT) and intensity-modulated radiotherapy ( IMRT) plans in children receiving craniospinal irradiation and estimate the risk of radiogenic second cancer according to the excess absolute risk ( EAR) model. Methods Computer-tomography scans of 15 children who received craniospinal irradiation between 2012 and 2017 were selected. HT and IMRT plans were designed for each patient after contouring the volumes of tumors and organ at risks ( OARs) and then the homogeneous index ( HI) , conformity index ( CI) , the maximum dose and the mean dose of OAR,V10 and V20 were analyzed to optimize the clinical treatment plan. The second cancer risk was estimated by DVH of each organ and EAR model and statistically compared between HT and IMRT. Results Both two plans met the clinical requirements in target coverage ( 100％ dose≥95％ target volume).The HI in the HT group was significantly superior to that in the IMRT group (P=0. 000) whereas no significant difference was noted in CI between two groups. Compared with the IMRT plan, HT plan possessed absolute advantage in protecting hippocampus and the D2％ and Dmean were significantly lower ( P=0. 000).As for the protection of OAR, the Dmax, Dmean and V20 of thyroid (P=0. 001,0. 002 and 0. 014) and Dmax,V10 of heart ( P=0. 001 and 0. 003) in the HT plan were significantly lower than those in the IMRT plan. In terms of second cancer risk, HT plan yielded a significantly higher second cancer risk for thyroid and lung compared with IMRT the EAR in thyroid was 28. 666 vs. 26. 926 ( P=0. 010 ) and 20. 496 vs. 18.922( P=0. 003) in lung. Both plans yielded a relatively high second cancer risk for stomach ( P=0. 248), whereas a low second cancer risk for liver (P=0. 020). Conclusions HT plan is superior to IMRT plan in the hippocampus-sparing craniospinal irradiation in children. However, HT plan yields a high second cancer risk for thyroid and lung. Consequently, the balance between the carcinogenic risk and the effect on other normal tissues should be assessed in the establishment of therapeutic plan.

Development and application of a rat PBPK model to elucidate kidney and liver effects induced by ETBE and tert-butanol.

Subchronic and chronic studies in rats of the gasoline oxygenates ethyl tert-butyl ether (ETBE) and tert-butanol (TBA) report similar noncancer kidney and liver effects but differing results with respect to kidney and liver tumors. Because TBA is a major metabolite of ETBE, it is possible that TBA is the active toxic moiety in all these studies, with reported differences due simply to differences in the internal dose. To test this hypothesis, a physiologically-based pharmacokinetic (PBPK) model was developed for ETBE and TBA to calculate internal dosimetrics of TBA following either TBA or ETBE exposure. This model, based on earlier PBPK models of methyl tert-butyl ether (MTBE), was used to evaluate whether kidney and liver effects are consistent across routes of exposure, as well as between ETBE and TBA studies, on the basis of estimated internal dose. The results demonstrate that noncancer kidney effects, including kidney weight changes, urothelial hyperplasia, and chronic progressive nephropathy (CPN), yielded consistent dose-response relationships across routes of exposure and across ETBE and TBA studies using TBA blood concentration as the dose metric. Relative liver weights were also consistent across studies on the basis of TBA metabolism, which is proportional to TBA liver concentrations. However, kidney and liver tumors were not consistent using any dose metric. These results support the hypothesis that TBA mediates the noncancer kidney and liver effects following ETBE administration; however, additional factors besides internal dose are necessary to explain the induction of liver and kidney tumors.

Improved genetic algorithm in optimization of beam orientation in intensity modulated radiotherapy / 中华放射肿瘤学杂志

manual beam orientation selection, beam orientation optimization which is feasible in IMRT planning may significantly improve the efficiency and result.