The response of a BGO scintillation detector to 100\u2013500 MeV kinetic energy pions, protons and deuterons

The light response of pions, protons and deuterons with respect to electrons of the same energy is measured in a BGO calorimeter using the inclusive 16O(e, e\u2032), 16O(e, \u3c0), 16O(e, p) and 16O(e, d) reactions. An average 5% quenching is found in the 100\u2013500 MeV energy range of this experiment

Factors affecting outcomes following pelvic exenteration for locally recurrent rectal cancer

Background: Pelvic exenteration for locally recurrent rectal cancer (LRRC) is associated with variable outcomes, with the majority of data from single-centre series. This study analysed data from an international collaboration to determine robust parameters that could inform clinical decision-making. Methods: Anonymized data on patients who had pelvic exenteration for LRRC between 2004 and 2014 were accrued from 27 specialist centres. The primary endpoint was survival. The impact of resection margin, bone resection, node status and use of neoadjuvant therapy (before exenteration) was assessed. Results: Of 1184 patients, 614 (51\ub79 per cent) had neoadjuvant therapy. A clear resection margin (R0 resection) was achieved in 55\ub74 per cent of operations. Twenty-one patients (1\ub78 per cent) died within 30 days and 380 (32\ub71 per cent) experienced a major complication. Median overall survival was 36 months following R0 resection, 27 months after R1 resection and 16 months following R2 resection (P < 0\ub7001). Patients who received neoadjuvant therapy had more postoperative complications (unadjusted odds ratio (OR) 1\ub753), readmissions (unadjusted OR 2\ub733) and radiological reinterventions (unadjusted OR 2\ub712). Three-year survival rates were 48\ub71 per cent, 33\ub79 per cent and 15 per cent respectively. Bone resection (when required) was associated with a longer median survival (36 versus 29 months; P < 0\ub7001). Node-positive patients had a shorter median overall survival than those with node-negative disease (22 versus 29 months respectively). Multivariable analysis identified margin status and bone resection as significant determinants of long-term survival. Conclusion: Negative margins and bone resection (where needed) were identified as the most important factors influencing overall survival. Neoadjuvant therapy before pelvic exenteration did not affect survival, but was associated with higher rates of readmission, complications and radiological reintervention

Minimally invasive surgery techniques in pelvic exenteration: a systematic and meta-analysis review

Background: Pelvic exenteration is potentially curative for locally advanced and recurrent pelvic cancers. Evolving technology has facilitated the use of minimally invasive surgical (MIS) techniques in selected cases. We aimed to compare outcomes between open and MIS pelvic exenteration. Methods: A review of comparative studies was performed. Firstly, we evaluated the differences in surgical techniques with respect to operative time, blood loss, and margin status. Secondly, we assessed differences in 30-day morbidity and mortality rates, and length of hospital stay. Results: Four studies that directly compared open and MIS exenteration were included. Analysis was performed on 170 patients; 78.1% (n = 133) had open pelvic exenteration, while 21.8% (n = 37) had a MIS exenteration. The median age for open exenteration was 57.7 years versus 63 years for MIS exenteration. Even though the operative time for MIS exenteration was 83 min longer (p < 0.001), it was associated with a median of 1,750mls less blood loss. The morbidity rate for MIS exenterative group was 56.7% (n = 21/37) versus 88.5% (n = 85/96) in the open exenteration group, with pooled analysis observing a 1.17 relative risk increase in 30-day morbidity (p = 0.172) in the open exenteration group. In addition, the MIS cohort had a 6-day shorter length of hospital stay (p = 0.04). Conclusion: MIS exenteration can be performed in highly selective cases, where there is favourable patient anatomy and tumour characteristics. When feasible, it is associated with reduced intra-operative blood loss, shorter length of hospital stay, and reduced morbidity

Palliative pelvic exenteration: A systematic review of patient-centered outcomes

Objective: Palliative pelvic exenteration (PPE) is a technically complex operation with high morbidity and mortality rates, considered in patients with limited life expectancy. There is little evidence to guide practice. We performed a systematic review to evaluate the impact of PPE on symptom relief and quality of life (QoL). Methods: A systematic review was conducted according to the PRISMA guidelines using Ovid MEDLINE, EMBASe, and PubMed databases for studies reporting on outcomes of PPE for symptom relief or QoL. Descriptive statistics were used on pooled patient cohorts. Results: Twenty-three historical cohorts and case series were included, comprising 509 patients. No comparative studies were found. Most malignancies were of colorectal, gynaecological and urological origin. Common indications for PPE were pain, symptomatic fistula, bleeding, malodour, obstruction and pelvic sepsis. The pooled median postoperative morbidity rate was 53.6% (13\u2013100%), the median in-hospital mortality was 6.3% (0\u201366.7%), and median OS was 14 months (4\u201340 months). Some symptom relief was reported in a median of 79% (50\u2013100%) of the patients, although the magnitude of effect was poorly measured. Data for QoL measures were inconclusive. Five studies discouraged performing PPE in any patient, while 18 studies concluded that the procedure can be considered in highly selected patients. Conclusion: Available evidence on PPE is of low-quality. Morbidity and mortality rates are high with a short median OS interval. While some symptom relief may be afforded by this procedure, evidence for improvement in QoL is limited. A highly selective individualised approach is required to optimise the risk:benefit equation

Predicting outcomes of pelvic exenteration using machine learning

Aim: We aim to compare machine learning with neural network performance in predicting R0 resection (R0), length of stay > 14 days (LOS), major complication rates at 30 days postoperatively (COMP) and survival greater than 1 year (SURV) for patients having pelvic exenteration for locally advanced and recurrent rectal cancer. Method: A deep learning computer was built and the programming environment was established. The PelvEx Collaborative database was used which contains anonymized data on patients who underwent pelvic exenteration for locally advanced or locally recurrent colorectal cancer between 2004 and 2014. Logistic regression, a support vector machine and an artificial neural network (ANN) were trained. Twenty per cent of the data were used as a test set for calculating prediction accuracy for R0, LOS, COMP and SURV. Model performance was measured by plotting receiver operating characteristic (ROC) curves and calculating the area under the ROC curve (AUROC). Results: Machine learning models and ANNs were trained on 1147 cases. The AUROC for all outcome predictions ranged from 0.608 to 0.793 indicating modest to moderate predictive ability. The models performed best at predicting LOS > 14 days with an AUROC of 0.793 using preoperative and operative data. Visualized logistic regression model weights indicate a varying impact of variables on the outcome in question. Conclusion: This paper highlights the potential for predictive modelling of large international databases. Current data allow moderate predictive ability of both complex ANNs and more classic methods