Systematic Analysis of Accuracy in Predicting Complete Oncological Resection in Pancreatic Cancer Patients—Proposal of a New Simplified Borderline Resectability Definition

Background: Borderline resectability in pancreatic cancer (PDAC) is currently debated. Methods: Patients undergoing pancreatic resections for PDAC were identified from a prospectively maintained database. As new borderline criteria, the presence of any superior mesenterico-portal vein alteration (SMPV) and perivascular stranding of the superior mesenteric artery (SMA) was evaluated in preoperative imaging. The accuracy of established radiological borderline criteria as compared to the new borderline criteria in predicting R status (sensitivity/negative predictive value) and overall survival was assessed. Results: 118 patients undergoing pancreatic resections for PDAC from 2013 to 2018 were identified. Forty-three (36.4%) had radiological perivascular SMA stranding and 55 (46.6%) had SMPV alterations. Interrater reliability was 90% for SMA stranding and 87% for SMPV alterations. The new borderline definition including SMPV alterations and perivascular SMA stranding was the best predictor of conventional R status (p = 0.040, sensitivity 53%, negative predictive value 81%) and Leeds/Wittekind circumferential margin status (p = 0.050, sensitivity 73%, negative predictive value 79%) as compared to established borderline resectability definition criteria. Perivascular SMA stranding qualified as an independent negative prognostic parameter (HR 3.066, 95% CI 1.078–5.716, p = 0.036). Conclusion: The radiological evaluation of any SMPV alteration and perivascular SMA stranding predicts R status and overall survival in PDAC patients, and may serve to identify potential candidates for neoadjuvant therapy.

Application of Dose-Volume Histogram Prediction in Biologically Related Models for Nasopharyngeal Carcinomas Treatment Planning

Purpose: In this study, we employed a gated recurrent unit (GRU)-based recurrent neural network (RNN) to predict the dose-volume histogram (DVH) and investigated the feasibility and usefulness of this method in biologically related models for nasopharyngeal carcinomas treatment planning.Methods and Materials: One hundred NPC patients were selected from a database containing clinical VMAT plans in recent two years; of these, the data from 80 patients were used to train the GRU-RNN, and the data of the other 20 patients were used for testing. For the prescribed doses of all the plans in 30 or 31 fractions, 70 Gy were delivered to PTV70 (the gross tumour volume with circumferential margin), 60 Gy were delivered to PTV60, 54 Gy were delivered to PTV54 and 66 Gy were delivered to PTV66 (lymph node gross tumour volume with circumferential margin). For each NPC patient, the DVHs of different organs at risk (OARs) were predicted by the trained GRU-based RNN using the information given by individual conformal beams. Based on the predictive DVHs, the equivalent uniform dose (EUD) were calculated, and directly applied as dose constrains in Treatment Planning optimization. The regenerated VMAT experimental plans (EPs) were evaluated by comparing them with the clinical plans (CPs).Results: For the 20 test patients, the regenerated EPs guided by the GRU-RNN predictive model achieved very good consistency relative to the CPs. The EPs showed better dose sparing for many OARs and significant differences were found in the maximum/mean doses to the brain stem, brain stem PRV, spinal cord, lenses, temporal lobes and parotids with P-values <0.05, respectively. On average, compared with the CPs, the maximum/mean doses to these OARs were altered by -3.44 Gy, -1.94 Gy, -1.88 Gy, 0.44 Gy, 1.98 Gy and -1.82 Gy, respectively.Conclusion: The GRU-RNN based DVH prediction method is capable of accurately and completely predicting the whole DVH for EUD calculation. The regenerated plans guided by the predictive EUD sparing were not inferior to the manual plans, indicating the great potential for improved planning and quality control in clinical applications.

The influence of disinfection on dimensional stability of temporary crowns

<p><strong>Objective</strong>: Evaluate the influence of different disinfection methods on the dimensional stability of temporary acrylic resin crowns. <strong>Material and Methods</strong>: A metallic die with two different marks at the margin was used to prepare the specimens with two different resins (bis-acrylic resin-Structur, acrylic resin-Dencrilay). They were divided into eight groups (n=8), determined according to the disinfection methods (microwave, acetic acid, 1% hypochlorite) and control. The marginal adaptation was recorded using an optical microscope (50X) comparing two different marks on the margin of the crowns with 2 points along the entire circumferential margin before and after disinfection methods. <strong>Results</strong>: Results were compared statistically by ANOVA and Tukey's test (p≤0.05). The two-way ANOVA showed statistical difference between types of materials. No significant differences were found between disinfection methods and interaction of factors. <strong>Conclusion:</strong> All procedures affected the marginal adaptation however temporary crowns made by bis-acrylic resin demonstrate higher dimensional stability.</p><p><strong>Keywords</strong></p><p>Dimensional stability; Disinfection; Temporary crowns.</p>