normal tissue complication probability
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Cancers ◽  
2021 ◽  
Vol 14 (1) ◽  
pp. 116
Author(s):  
Ramon Ortiz ◽  
Ludovic De Marzi ◽  
Yolanda Prezado

(1) Background: Proton Arc Therapy and Proton Minibeam Radiation Therapy are two novel therapeutic approaches with the potential to lower the normal tissue complication probability, widening the therapeutic window for radioresistant tumors. While the benefits of both modalities have been individually evaluated, their combination and its potential advantages are being assessed in this proof-of-concept study for the first time. (2) Methods: Monte Carlo simulations were employed to evaluate the dose and LET distributions in brain tumor irradiations. (3) Results: a net reduction in the dose to normal tissues (up to 90%), and the preservation of the spatial fractionation of the dose were achieved for all configurations evaluated. Additionally, Proton Minibeam Arc Therapy (pMBAT) reduces the volumes exposed to high-dose and high-LET values at expense of increased low-dose and intermediate-LET values. (4) Conclusions: pMBAT enhances the individual benefits of proton minibeams while keeping those of conventional proton arc therapy. These results might facilitate the path towards patients’ treatments since lower peak doses in normal tissues would be needed than in the case of a single array of proton minibeams.


Cancers ◽  
2021 ◽  
Vol 13 (21) ◽  
pp. 5584
Author(s):  
Urszula Smyczynska ◽  
Szymon Grabia ◽  
Zuzanna Nowicka ◽  
Anna Papis-Ubych ◽  
Robert Bibik ◽  
...  

State-of-art normal tissue complication probability (NTCP) models do not take into account more complex individual anatomical variations, which can be objectively quantitated and compared in radiomic analysis. The goal of this project was development of radiomic NTCP model for radiation-induced hypothyroidism (RIHT) using imaging biomarkers (radiomics). We gathered CT images and clinical data from 98 patients, who underwent intensity-modulated radiation therapy (IMRT) for head and neck cancers with a planned total dose of 70.0 Gy (33–35 fractions). During the 28-month (median) follow-up 27 patients (28%) developed RIHT. For each patient, we extracted 1316 radiomic features from original and transformed images using manually contoured thyroid masks. Creating models based on clinical, radiomic features or a combination thereof, we considered 3 variants of data preprocessing. Based on their performance metrics (sensitivity, specificity), we picked best models for each variant ((0.8, 0.96), (0.9, 0.93), (0.9, 0.89) variant-wise) and compared them with external NTCP models ((0.82, 0.88), (0.82, 0.88), (0.76, 0.91)). We showed that radiomic-based models did not outperform state-of-art NTCP models (p > 0.05). The potential benefit of radiomic-based approach is that it is dose-independent, and models can be used prior to treatment planning allowing faster selection of susceptible population.


PLoS ONE ◽  
2021 ◽  
Vol 16 (10) ◽  
pp. e0259112
Author(s):  
Valeria Meier ◽  
Felicitas Czichon ◽  
Linda Walsh ◽  
Carla Rohrer Bley

Intensity modulated radiation therapy (IMRT) introduced marked changes to cancer treatment in animals by reducing dose to organs at risk (OAR). As the next technological step, volumetric modulated arc therapy (VMAT) has advantages (increased degrees-of-freedom, faster delivery) compared to fixed-field IMRT. Our objective was to investigate a possible advantage of VMAT over IMRT in terms of lower OAR doses in advanced-disease sinonasal tumors in dogs treated with simultaneously-integrated boost radiotherapy. A retrospective, analytical, observational study design was applied using 10 pre-existing computed tomography datasets on dogs with stage 4 sinonasal tumors. Each dataset was planned with both, 5-field IMRT and 2 arc VMAT with 10x4.83 Gy to the gross tumor volume and 10x4.2 Gy to the planning target volume. Adequate target dose coverage and normal tissue complication probability of brain ≤5% was required. Dose constraints aspired to were D60 <15 Gy for eyes, D2 <35.4 Gy for corneae, and Dmean <20 Gy for lacrimal glands. OAR dose was statistically significantly higher in IMRT plans than in VMAT plans. Median eye D60% was 18.5 Gy (interquartile range (IQR) 17.5) versus 16.1 Gy (IQR 7.4) (p = 0.007), median lacrimal gland dose 21.8 Gy (IQR 20.5) versus 18.6 Gy (IQR 7.0) (p = 0.013), and median cornea D2% 45.5 Gy (IQR 6.8) versus 39.9 Gy (IQR 10.0) (p<0.005) for IMRT versus VMAT plans, respectively. Constraints were met in 21/40 eyes, 7/40 corneae, and 24/40 lacrimal glands. Median delivery time was significantly longer for IMRT plans than for VMAT plans (p<0.01). Based on these results, VMAT plans were found to be superior in sparing doses to eyes, lacrimal glands, corneae. However, not all ocular OAR constraints could be met while ensuring adequate dose coverage and restricting brain toxicity risk for both planning techniques.


Cancers ◽  
2021 ◽  
Vol 13 (20) ◽  
pp. 5092
Author(s):  
Kim Melanie Kraus ◽  
Cristoforo Simonetto ◽  
Pavel Kundrát ◽  
Vanessa Waitz ◽  
Kai Joachim Borm ◽  
...  

We investigated the potential of respiratory gating to mitigate the motion-caused misdosage in lung stereotactic body radiotherapy (SBRT). For fourteen patients with lung tumors, we investigated treatment plans for a gating window (GW) including three breathing phases around the maximum exhalation phase, GW40-60. For a subset of six patients, we also assessed a preceding three-phase GW20-40 and six-phase GW20-70. We analyzed the target volume, lung, esophagus, and heart doses. Using normal tissue complication probability (NTCP) models, we estimated radiation pneumonitis and esophagitis risks . Compared to plans without gating, GW40-60 significantly reduced doses to organs at risk without impairing the tumor doses. On average, the mean lung dose decreased by 0.6 Gy (p < 0.001), treated lung V20Gy by 2.4% (p = 0.003), esophageal dose to 5cc by 2.0 Gy (p = 0.003), and maximum heart dose by 3.2 Gy (p = 0.009). The model-estimated mean risks of 11% for pneumonitis and 12% for esophagitis without gating decreased upon GW40-60 to 7% and 9%, respectively. For the highest-risk patient, gating reduced the pneumonitis risk from 43% to 32%. Gating is most beneficial for patients with high-toxicity risks. Pre-treatment toxicity risk assessment may help optimize patient selection for gating, as well as GW selection for individual patients.


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