Reduction of energy input in wire arc additive manufacturing (WAAM) with gas metal arc welding (GMAW)

Wire arc additive manufacturing (WAAM) by gas metal arc welding (GMAW) is a suitable option for the production of large volume metal parts. The main challenge is the high and periodic heat input of the arc on the generated layers, which directly affects geometrical features of the layers such as height and width as well as metallurgical properties such as grain size, solidification or material hardness. Therefore, processing with reduced energy input is necessary. This can be implemented with short arc welding regimes and respectively energy reduced welding processes. A highly efficient strategy for further energy reduction is the adjustment of contact tube to work piece distance (CTWD) during the welding process. Based on the current controlled GMAW process an increase of CTWD leads to a reduction of the welding current due to increased resistivity in the extended electrode and constant voltage of the power source. This study shows the results of systematically adjusted CTWD duringWAAM of low-alloyed steel. Thereby, an energy reduction of up to 40% could be implemented leading to an adaptation of geometrical and microstructural features of additively manufactured work pieces

Wire arc additive manufacturing (WAAM) of aluminium alloy AlMg5Mn with energy-reduced gas metal arc welding (GMAW)

Large-scale aluminum parts are used in aerospace and automotive industries, due to excellent strength, light weight, and the good corrosion resistance of the material. Additive manufacturing processes enable both cost and time savings in the context of component manufacturing. Thereby, wire arc additive manufacturing (WAAM) is particularly suitable for the production of large volume parts due to deposition rates in the range of kilograms per hour. Challenges during the manufacturing process of aluminum alloys, such as porosity or poor mechanical properties, can be overcome by using arc technologies with adaptable energy input. In this study, WAAM of AlMg5Mn alloy was systematically investigated by using the gas metal arc welding (GMAW) process. Herein, correlations between the energy input and the resulting temperature–time-regimes show the effect on resulting microstructure, weld seam irregularities and the mechanical properties of additively manufactured aluminum parts. Therefore, multilayer walls were built layer wise using the cold metal transfer (CMT) process including conventional CMT, CMT advanced and CMT pulse advanced arc modes. These processing strategies were analyzed by means of energy input, whereby the geometrical features of the layers could be controlled as well as the porosity to area portion to below 1% in the WAAM parts. Furthermore, the investigations show the that mechanical properties like tensile strength and material hardness can be adapted throughout the energy input per unit length significantl

Risk factors for bladder neck contracture after transurethral resection of the prostate

Introduction Transurethral resection of the prostate (TURP) is the most frequently used treatment of benign prostate hyperplasia with a prostate volume of <80 mL. A long-term complication is bladder neck contracture (BNC). The aim of the present study was to identify the risk factors for BNC formation after TURP. Methods We conducted a retrospective analysis of all TURP primary procedures which were performed at one academic institution between 2013 and 2018. All patients were analyzed and compared with regard to postoperative formation of a BNC requiring further therapy. Uni- and multivariable logistic regression analyses (MVAs) were performed to identify possible risk factors for BNC development. Results We included 1368 patients in this analysis. Out of these, 88 patients (6.4%) developed BNC requiring further surgical therapy. The following factors showed a statistically significant association with BNC development: smaller preoperative prostate volume (p = 0.001), lower resected prostate weight (p = 0.004), lower preoperative levels of prostate-specific antigen (PSA, p < 0.001), shorter duration of the surgery (p = 0.027), secondary transurethral intervention (due to urinary retention or gross hematuria) during inpatient stay (p = 0.018), positive (≥100  CFU/mL) preoperative urine culture (p = 0.010), and urethral stricture (US) formation requiring direct visual internal urethrotomy (DVIU) postoperatively after TURP (p < 0.001), in particular membranous (p = 0.046) and bulbar (p < 0.001) strictures. Preoperative antibiotic treatment showed a protective effect (p = 0.042). Histopathological findings of prostate cancer (PCA) in the resected prostate tissue were more frequent among patients who did not develop BNC (p = 0.049). On MVA, smaller preoperative prostate volume (p = 0.046), positive preoperative urine culture (p = 0.021), and US requiring DVIU after TURP (p < 0.001) were identified as independent predictors for BNC development. Conclusion BNC is a relevant long-term complication after TURP. In particular, patients with a smaller prostate should be thoroughly informed about this complication

Short-Term and Long-Term Morbidity after Radical Cystectomy in Patients with NMIBC and Comparison with MIBC: Identifying Risk Factors for Severe Short-Term Complications

Introduction: RC represents a viable treatment option for certain NMIBC patients. However, studies investigating morbidity in the context of RC for NMIBC are scarce. The goal of the current study was to assess and compare morbidity after RC performed in patients with NMIBC and patients with MIBC and to identify risk factors for severe short-term complications. Methods: Medical records of 521 patients who underwent RC for bladder cancer were retrospectively reviewed. Patients were divided into patients with NMIBC and patients with MIBC. The groups were compared and risk factors for severe complications were identified. Results: RC for NMIBC was performed in 123 patients (23.6%). Histological upstaging was seen in 47 NMIBC patients (38.2%) and in 231 MIBC patients (58%, p < 0.001). OS was 29.8% and CSS was 15.5%. Both endpoints were higher for RC for MIBC (p < 0.001). More complications affecting the urinary diversion were seen with RC for NMIBC (p = 0.033) and more continent urinary diversions (p = 0.040) were performed in those patients. Obesity (p = 0.008), a higher ASA score (p = 0.004), and preoperative medical drug anticoagulation (p = 0.025) were risk factors for severe short-term morbidity after both, RC for NMIBC and for MIBC. Conclusion: Patients who underwent RC for NMIBC are exposed to a comparably high perioperative risk than patients with MIBC. RC seems to be a viable treatment option for certain NMIBC patients with a significant histological upstaging in both groups. In patients with obesity, a high ASA score, and with medical drug anticoagulation, the indication for surgery should be confirmed especially strict and possible treatment alternatives should be considered particularly thorough

Tumor budding correlates with tumor invasiveness and predicts worse survival in pT1 non-muscle-invasive bladder cancer

Tumor budding is defined as a single cell or a cluster of up to 5 tumor cells at the invasion front. Due to the difficulty of identifying patients at high risk for pT1 non-muscle-invasive bladder cancer (NMIBC) and the difficulties in T1 substaging, tumor budding was evaluated as a potential alternative and prognostic parameter in these patients. Tumor budding as well as growth pattern, invasion pattern and lamina propria infiltration were retrospectively evaluated in transurethral resection of the bladder (TURB) specimens from 92 patients with stage pT1 NMIBC. The presence of tumor budding correlated with multifocal tumors (p = 0.003), discontinuous invasion pattern (p = 0.039), discohesive growth pattern (p < 0.001) and extensive lamina propria invasion (p < 0.001). In Kaplan–Meier analysis, tumor budding was associated with significantly worse RFS (p = 0.005), PFS (p = 0.017) and CSS (p = 0.002). In patients who received BCG instillation therapy (n = 65), the absence of tumor budding was associated with improved RFS (p = 0.012), PFS (p = 0.011) and CSS (p = 0.022), with none of the patients suffering from progression or dying from the disease. Tumor budding is associated with a more aggressive and invasive stage of pT1 NMIBC and a worse outcome. This easy-to-assess parameter could help stratify patients into BCG therapy or early cystectomy treatment groups

Outcome of Patients with Pathological Tumor Stage T3 Urothelial Carcinoma of the Bladder following Radical Cystectomy in a Single-Center Series with 116 Patients

Objective: Outcome prediction of pT3 urothelial carcinoma of the bladder (UCB) after radical cystectomy (RC) remains challenging. The objective of our study was to determine high-risk patients with poor survival outcome in a heterogeneous group substaged pT3 who might profit from early adjuvant chemotherapy. Materials and Methods: We compiled clinicopathological and immunohistochemical data of E-cadherin (E-cad) expression in 116 patients with pT3 UCB after RC in our single-center series. Multivariable Cox regression models including substaged pT3 established clinicopathological features, and the expression of the predictive immunohistochemical feature E-cad was used to identify independent predictors on progression-free (PFS), cancer-specific (CSS) and overall survival (OS), respectively. Results: No significant differences were found addressing clinicopathological data and substaged pT3. In multivariable Cox regression models, lymph node involvement was an independent predictor for PFS (p < 0.001), CSS (p < 0.001) and OS (p = 0.002), respectively. Lymphovascular invasion (LVI) significantly influenced PFS (p = 0.016). ASA score 3/4 independently predicted CSS (p = 0.049) and OS (p = 0.032). Neither pT3 substages nor E-cad expression were significant prognosticators for survival. Conclusions: In pT3 UCB patients with ASA 3/4, positive lymph node status and/or presence of LVI, administration of chemotherapy should be considered due to the high risk of poor oncological outcome. The immunohistochemical marker E-cad was not an independent predictor

Preoperative C-Reactive Protein in the Serum: A Prognostic Biomarker for Upper Urinary Tract Urothelial Carcinoma Treated with Radical Nephroureterectomy

Objective: To investigate the impact of preoperative serum C-reactive protein (CRP) on clinicopathological features and prognosis in patients with upper tract urothelial cancer (UTUC) after radical nephroureterectomy (RNU). Patients andMethods: Data of 265 patients from three German centers who underwent RNU for UTUC without neoadjuvant chemotherapy between 1990 and 2012 were evaluated. Mean follow-up was 37 months (interquartile range 9-48). CRP was analyzed as a categorical and continuous variable for the prediction of recurrence-free survival (RFS), disease-specific survival (DSS) and all-cause survival (ACS) using uni- and multivariate Cox regression analyses. Results: The optimal cutoff for CRP was calculated by the Youden index at 0.90 mg/dl. Elevated CRP was significantly associated with pT3/4 and pN+ in a preoperative model including age, gender, tumor multifocality, tumor localization and the Eastern Cooperative Oncology Group Performance Status. In a multivariable Cox regression model adjusted for features significant in univariable analysis, categorized and continuous CRP levels were both independent predictors for RFS [hazard ratio (HR) 1.18, p = 0.050; HR 1.03, p = 0.012] and DSS (HR 1.61, p = 0.026; HR 1.06, p = 0.001). Continuous CRP was an independent predictor for ACS (HR 1.05, p = 0.036). Conclusions: Elevated preoperative CRP is significantly associated with aggressive tumor biology and an independent predictor for poor survival after RNU. Preoperative serum CRP represents an easily obtainable and cost-effective marker in UTUC and may help in counseling patients with regard to operative management and/or adjuvant or neoadjuvant therapies

The Charlson Comorbidity Index Predicts Survival after Disease Recurrence in Patients following Radical Cystectomy for Urothelial Carcinoma of the Bladder

Objective: To identify prognostic clinical and histopathological parameters, including comorbidity indices at the time of radical cystectomy (RC), for overall survival (OS) after recurrence following RC for urothelial carcinoma of the bladder (UCB). Materials and Methods: A retrospective multicenter study was carried out in 555 unselected consecutive patients who underwent RC with pelvic lymph node dissection for UCB from 2000 to 2010. A total of 227 patients with recurrence comprised our study group. Cox proportional hazards regression models were calculated with established variables to assess their independent influence on OS after recurrence. Results: The median time from RC to recurrence and the median OS after recurrence was 10.9 and 5.4 months, respectively. Neither the time to recurrence nor the type of recurrence (systematic vs. local) was predictive of the OS. In contrast, age (hazard ratio (HR) 1.53, p = 0.011), lymph node metastasis (HR 1.56, p = 0.007), and positive surgical margins (HR 1.53, p = 0.046) significantly affected the OS after disease recurrence. In addition, the dichotomized Charlson comorbidity index (CCI; dichotomized into >2 vs. 0-2) was the only comorbidity score with an independent prediction of OS (HR 1.41, p = 0.033). We observed a significant gain in the base model's predictive accuracy, i.e. from 68.4 to 70.3% (p < 0.001), after inclusion of the dichotomized CCI. Conclusions: We present the first outcome study of comorbidity indices used as predictors of OS after disease recurrence in patients undergoing RC for UCB. The CCI at the time of RC had no significant influence on the time to recurrence but represented an independent predictor of OS after disease recurrence

Prediction of Locally Advanced Urothelial Carcinoma of the Bladder Using Clinical Parameters before Radical Cystectomy - A Prospective Multicenter Study

Introduction: We aimed at developing and validating a pre-cystectomy nomogram for the prediction of locally advanced urothelial carcinoma of the bladder (UCB) using clinicopathological parameters. Materials and Methods: Multicenter data from 337 patients who underwent radical cystectomy (RC) for UCB were prospectively collected and eligible for final analysis. Univariate and multivariate logistic regression models were applied to identify significant predictors of locally advanced tumor stage (pT3/4 and/or pN+) at RC. Internal validation was performed by bootstrapping. The decision curve analysis (DCA) was done to evaluate the clinical value. Results: The distribution of tumor stages pT3/4, pN+ and pT3/4 and/or pN+ at RC was 44.2, 27.6 and 50.4%, respectively. Age (odds ratio (OR) 0.980; p < 0.001), advanced clinical tumor stage (cT3 vs. cTa, cTis, cT1; OR 3.367; p < 0.001), presence of hydronephrosis (OR 1.844; p = 0.043) and advanced tumor stage T3 and/or N+ at CT imaging (OR 4.378; p < 0.001) were independent predictors for pT3/4 and/or pN+ tumor stage. The predictive accuracy of our nomogram for pT3/4 and/or pN+ at RC was 77.5%. DCA for predicting pT3/4 and/or pN+ at RC showed a clinical net benefit across all probability thresholds. Conclusion: We developed a nomogram for the prediction of locally advanced tumor stage pT3/4 and/or pN+ before RC using established clinicopathological parameters

Epidemiology and therapy of symptomatic lymphoceles after robot-assisted radical prostatectomy (RARP)

Background: Lymphoceles are a common postoperative complication after radical prostatectomy with pelvic lymphadenectomy. Therapeutic options include cannulation and drainage (CD), drainage and instillation (DI), or laparoscopic fenestration (LF). The aim of this study was to investigate the epidemiology of symptomatic lymphoceles (SLC) and evaluate the treatment options. Methods: We retrospectively analysed all patients who underwent robot-assisted radical prostatectomy (RARP) at our clinic from January 1, 2014 to December 31, 2018. All documented lymphoceles of these patients were recorded and analysed with regard to symptoms, possible infection and the treatment option (or options) chosen. Results: We were able to include all 1,029 patients who underwent RARP in the aforementioned period of time. Of these, 18.1% were diagnosed with a lymphocele either when discharged or when readmitted and 6.9% experienced an SLC requiring treatment. Thirteen-point-seven percent of patients readmitted with SLC showed an accompanying thrombosis. Due to recurring or bilateral SLCs receiving different treatment options for each side, there was a total of 115 SLCs treated. CD was carried out in 102 cases. Twenty-point six percent of patients were sufficiently treated this way, the rest required further treatment or experienced recurrences not requiring further treatment. DI was carried out in 56 cases. Of those patients, 46.4% were sufficiently treated. LF was carried out in 54 cases (either after CD, or after DI, or primarily). Of those patients, 98.1% were treated sufficiently. LF had a statistically significant higher success rate compared to CD and DI (P<0.001 respectively). Conclusions: The study confirmed the significance of SLC as a common complication after RARP. LF turned out to be the most effective treatment option for SLC, while CD as well as DI have not been proven effective