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result(s) for
"Van Calster, B"
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A simulation study of sample size demonstrated the importance of the number of events per variable to develop prediction models in clustered data
2015
This study aims to investigate the influence of the amount of clustering [intraclass correlation (ICC) = 0%, 5%, or 20%], the number of events per variable (EPV) or candidate predictor (EPV = 5, 10, 20, or 50), and backward variable selection on the performance of prediction models.
Researchers frequently combine data from several centers to develop clinical prediction models. In our simulation study, we developed models from clustered training data using multilevel logistic regression and validated them in external data.
The amount of clustering was not meaningfully associated with the models' predictive performance. The median calibration slope of models built in samples with EPV = 5 and strong clustering (ICC = 20%) was 0.71. With EPV = 5 and ICC = 0%, it was 0.72. A higher EPV related to an increased performance: the calibration slope was 0.85 at EPV = 10 and ICC = 20% and 0.96 at EPV = 50 and ICC = 20%. Variable selection sometimes led to a substantial relative bias in the estimated predictor effects (up to 118% at EPV = 5), but this had little influence on the model's performance in our simulations.
We recommend at least 10 EPV to fit prediction models in clustered data using logistic regression. Up to 50 EPV may be needed when variable selection is performed.
Journal Article
Randomized Trial of Fetal Surgery for Severe Left Diaphragmatic Hernia
by
Johnson, Anthony
,
Sago, Haruhiko
,
Deprest, Jan A
in
Adult
,
Airway management
,
Balloon Occlusion - adverse effects
2021
In this trial involving fetuses with severe left congenital diaphragmatic hernia, fetoscopic endoluminal tracheal occlusion at 27 to 29 weeks of gestation significantly increased survival to discharge, but it resulted in an increased incidence of preterm, prelabor rupture of membranes and preterm birth.
Journal Article
Clinical study investigating the role of lymphadenectomy, surgical castration and adjuvant hormonal treatment in endometrial stromal sarcoma
by
De Knijf, A
,
Van Huffel, S
,
Van Calster, B
in
Adolescent
,
Adult
,
Biological and medical sciences
2007
The objective of this study is to assess the therapeutic importance of surgical castration, adjuvant hormonal treatment and lymphadenectomy in endometrial stromal sarcoma (ESS). A retrospective and multicentric search was performed. Clinicopathologic data were retrieved from cases that were confirmed to be ESS after central pathology review. The protocol was approved by the Ethical Committee. ESS was confirmed histopathologically in 34 women, but follow-up data were available in only 31 women. Surgical treatment (
n
=31) included hysterectomy with or without bilateral salpingo-oophorectomy (BSO) in 23 out of 31 (74%) and 8 out of 31 (26%) cases, respectively. Debulking surgery was performed in 6 out of 31 cases (19%). Stage distribution was as follows: 22 stage I, 4 stage III and 5 stage IV. Women with stage I disease recurred in 4 out of 22 (18%) cases. Among stage I women undergoing hormonal treatment with or without BSO, 3 out of 15 (20%) and 1 out of 7 (14%) relapsed, respectively. Among stages III–IV women receiving adjuvant hormonal treatment or not, 1 out of 5 (20%) and 3 out of 4 (75%) relapsed, respectively (differences=55.0%, 95% CI=−6.8–81.2%). Kaplan–Meier curves show comparable recurrence rates for stage I disease without adjuvant hormonal treatment when compared to stages III–IV disease treated with surgery and adjuvant hormonal treatment. Furthermore, women taking hormones at diagnosis have a better outcome when compared to women not taking hormonal treatment. Three out of 31 (9%) patients had a systematic lymphadenectomy whereas 3 out of 31 (9%) had a lymph node sampling. In one case, obvious nodal disease was encountered at presentation. Isolated retroperitoneal recurrence occurred in 1 out of 31 (3%) of all cases and in 1 out of 8 (13%) recurrences. This single woman later also developed lung and abdominal metastases. Leaving lymph nodes
in situ
does not appear to alter the clinical outcome of ESS. Although numbers are low, the retrospective data suggest that the need for surgical castration (BSO) in premenopausal women with early-stage disease should be discussed with the patient on an individual basis. The data support the current practice in some centres to administer adjuvant hormonal treatment.
Journal Article
Evaluating the risk of ovarian cancer before surgery using the ADNEX model to differentiate between benign, borderline, early and advanced stage invasive, and secondary metastatic tumours: prospective multicentre diagnostic study
by
Bourne, Tom
,
Timmerman, Dirk
,
Testa, Antonia C
in
Adnexal Diseases - diagnostic imaging
,
Adnexal Diseases - pathology
,
Adult
2014
Objectives To develop a risk prediction model to preoperatively discriminate between benign, borderline, stage I invasive, stage II-IV invasive, and secondary metastatic ovarian tumours.Design Observational diagnostic study using prospectively collected clinical and ultrasound data.Setting 24 ultrasound centres in 10 countries.Participants Women with an ovarian (including para-ovarian and tubal) mass and who underwent a standardised ultrasound examination before surgery. The model was developed on 3506 patients recruited between 1999 and 2007, temporally validated on 2403 patients recruited between 2009 and 2012, and then updated on all 5909 patients.Main outcome measures Histological classification and surgical staging of the mass.Results The Assessment of Different NEoplasias in the adneXa (ADNEX) model contains three clinical and six ultrasound predictors: age, serum CA-125 level, type of centre (oncology centres v other hospitals), maximum diameter of lesion, proportion of solid tissue, more than 10 cyst locules, number of papillary projections, acoustic shadows, and ascites. The area under the receiver operating characteristic curve (AUC) for the classic discrimination between benign and malignant tumours was 0.94 (0.93 to 0.95) on temporal validation. The AUC was 0.85 for benign versus borderline, 0.92 for benign versus stage I cancer, 0.99 for benign versus stage II-IV cancer, and 0.95 for benign versus secondary metastatic. AUCs between malignant subtypes varied between 0.71 and 0.95, with an AUC of 0.75 for borderline versus stage I cancer and 0.82 for stage II-IV versus secondary metastatic. Calibration curves showed that the estimated risks were accurate.Conclusions The ADNEX model discriminates well between benign and malignant tumours and offers fair to excellent discrimination between four types of ovarian malignancy. The use of ADNEX has the potential to improve triage and management decisions and so reduce morbidity and mortality associated with adnexal pathology.
Journal Article
Evaluating the risk of ovarian cancer before surgery using the ADNEX model: a multicentre external validation study
2016
Background:
The International Ovarian Tumour Analysis (IOTA) group have developed the ADNEX (The Assessment of Different NEoplasias in the adneXa) model to predict the risk that an ovarian mass is benign, borderline, stage I, stages II–IV or metastatic. We aimed to externally validate the ADNEX model in the hands of examiners with varied training and experience.
Methods:
This was a multicentre cross-sectional cohort study for diagnostic accuracy. Patients were recruited from three cancer centres in Europe. Patients who underwent transvaginal ultrasonography and had a histological diagnosis of surgically removed tissue were included. The diagnostic performance of the ADNEX model with and without the use of CA125 as a predictor was calculated.
Results:
Data from 610 women were analysed. The overall prevalence of malignancy was 30%. The area under the receiver operator curve (AUC) for the ADNEX diagnostic performance to differentiate between benign and malignant masses was 0.937 (95% CI: 0.915–0.954) when CA125 was included, and 0.925 (95% CI: 0.902–0.943) when CA125 was excluded. The calibration plots suggest good correspondence between the total predicted risk of malignancy and the observed proportion of malignancies. The model showed good discrimination between the different subtypes.
Conclusions:
The performance of the ADNEX model retains its performance on external validation in the hands of ultrasound examiners with varied training and experience.
Journal Article
Strategies to diagnose ovarian cancer: new evidence from phase 3 of the multicentre international IOTA study
by
Franchi, D
,
Savelli, L
,
Fischerova, D
in
692/699/67/1517/1709
,
692/700/139
,
692/700/1421/1860
2014
Background:
To compare different ultrasound-based international ovarian tumour analysis (IOTA) strategies and risk of malignancy index (RMI) for ovarian cancer diagnosis using a meta-analysis approach of centre-specific data from IOTA3.
Methods:
This prospective multicentre diagnostic accuracy study included 2403 patients with 1423 benign and 980 malignant adnexal masses from 2009 until 2012. All patients underwent standardised transvaginal ultrasonography. Test performance of RMI, subjective assessment (SA) of ultrasound findings, two IOTA risk models (LR1 and LR2), and strategies involving combinations of IOTA simple rules (SRs), simple descriptors (SDs) and LR2 with and without SA was estimated using a meta-analysis approach. Reference standard was histology after surgery.
Results:
The areas under the receiver operator characteristic curves of LR1, LR2, SA and RMI were 0.930 (0.917–0.942), 0.918 (0.905–0.930), 0.914 (0.886–0.936) and 0.875 (0.853–0.894). Diagnostic one-step and two-step strategies using LR1, LR2, SR and SD achieved summary estimates for sensitivity 90–96%, specificity 74–79% and diagnostic odds ratio (DOR) 32.8–50.5. Adding SA when IOTA methods yielded equivocal results improved performance (DOR 57.6–75.7). Risk of Malignancy Index had sensitivity 67%, specificity 91% and DOR 17.5.
Conclusions:
This study shows all IOTA strategies had excellent diagnostic performance in comparison with RMI. The IOTA strategy chosen may be determined by clinical preference.
Journal Article
Multicentre external validation of IOTA prediction models and RMI by operators with varied training
by
Johnson, S
,
Raslan, F
,
Stalder, C
in
Adult
,
Biological and medical sciences
,
Biomedical and Life Sciences
2013
Background:
Correct characterisation of ovarian tumours is critical to optimise patient care. The purpose of this study is to evaluate the diagnostic performance of the International Ovarian Tumour Analysis (IOTA) logistic regression model (LR2), ultrasound Simple Rules (SR), the Risk of Malignancy Index (RMI) and subjective assessment (SA) for preoperative characterisation of adnexal masses, when ultrasonography is performed by examiners with different background training and experience.
Methods:
A 2-year prospective multicentre cross-sectional study. Thirty-five level II ultrasound examiners contributed in three UK hospitals. Transvaginal ultrasonography was performed using a standardised approach. The final outcome was the surgical findings and histological diagnosis. To characterise the adnexal masses, the six-variable prediction model (LR2) with a cutoff of 0.1, the RMI with cutoff of 200, ten SR (five rules for malignancy and five rules for benignity) and SA were applied. The area under the curves (AUCs) for performance of LR2 and RMI were calculated. Diagnostic performance measures for all models assessed were sensitivity, specificity, positive and negative likelihood ratios (LR+ and LR−), and the diagnostic odds ratio (DOR).
Results:
Nine-hundred and sixty-two women with adnexal masses underwent transvaginal ultrasonography, whereas 255 had surgery. Prevalence of malignancy was 29% (49 primary invasive epithelial ovarian cancers, 18 borderline ovarian tumours, and 7 metastatic tumours). The AUCs for LR2 and RMI for all masses were 0.94 (95% confidence interval (CI): 0.89–0.97) and 0.90 (95% CI: 0.83–0.94), respectively. In premenopausal women, LR2−RMI difference was 0.09 (95% CI: 0.03–0.15) compared with −0.02 (95% CI: −0.08 to 0.04) in postmenopausal women. For all masses, the DORs for LR2, RMI, SR+SA (using SA when SR inapplicable), SR+MA (assuming malignancy when SR inapplicable), and SA were 62 (95% CI: 27–142), 43 (95% CI: 19–97), 109 (95% CI: 44–274), 66 (95% CI: 27–158), and 70 (95% CI: 30–163), respectively.
Conclusion:
Overall, the test performance of IOTA prediction models and rules as well as the RMI was maintained in examiners with varying levels of training and experience.
Journal Article
Untapped potential of multicenter studies: a review of cardiovascular risk prediction models revealed inappropriate analyses and wide variation in reporting
2019
Background
Clinical prediction models are often constructed using multicenter databases. Such a data structure poses additional challenges for statistical analysis (clustered data) but offers opportunities for model generalizability to a broad range of centers. The purpose of this study was to describe properties, analysis, and reporting of multicenter studies in the Tufts PACE Clinical Prediction Model Registry and to illustrate consequences of common design and analyses choices.
Methods
Fifty randomly selected studies that are included in the Tufts registry as multicenter and published after 2000 underwent full-text screening. Simulated examples illustrate some key concepts relevant to multicenter prediction research.
Results
Multicenter studies differed widely in the number of participating centers (range 2 to 5473). Thirty-nine of 50 studies ignored the multicenter nature of data in the statistical analysis. In the others, clustering was resolved by developing the model on only one center, using mixed effects or stratified regression, or by using center-level characteristics as predictors. Twenty-three of 50 studies did not describe the clinical settings or type of centers from which data was obtained. Four of 50 studies discussed neither generalizability nor external validity of the developed model.
Conclusions
Regression methods and validation strategies tailored to multicenter studies are underutilized. Reporting on generalizability and potential external validity of the model lacks transparency. Hence, multicenter prediction research has untapped potential.
Registration
This review was not registered.
Journal Article
Neoadjuvant chemotherapy followed by interval debulking surgery in patients with serous endometrial cancer with transperitoneal spread (stage IV): a new preferred treatment?
by
Moerman, Ph
,
Van Calster, B
,
Berteloot, P
in
Adenocarcinoma, Clear Cell - drug therapy
,
Adenocarcinoma, Clear Cell - pathology
,
Adenocarcinoma, Clear Cell - surgery
2009
Background:
To investigate the value of neoadjuvant chemotherapy (NACT), followed by interval debulking surgery (IDS), in endometrial cancer with transperitoneal spread (stage IV).
Methods:
Patients with endometrial cancer with transperitoneal spread, as determined by laparoscopy (±pleural effusion), were treated with NACT. Efficacy was determined according to the Response Evaluation Criteria in Solid Tumors, residual tumour at IDS and histopathological assessment of tumour regression.
Results:
A total of 30 patients (median age: 65 years; range:44–81 years) received 3–4 cycles of NACT (83% paclitaxel/carboplatin). Histopathological subtypes were as follows: serous (90%), clear cell (3%) and endometrioid (6%) carcinoma. Response according to RECIST was as follows: 2 (7%) complete remission, 20 (67%) partial remission, 6 (20%) stable disease and 2 (7%) progressive disease (PD). Patients with PD were not operated upon. A total of 24 patients (80%) had optimal cytoreduction (
R
⩽1 cm), of whom 22 (92%) were without residual tumour. Four patients were considered inoperable and were excluded from further analysis. The median progression-free survival and overall survival times were 13 and 23 months, respectively.
Histopathological features of chemoresponse in both uterus and omentum were related to a better PFS (
P
=0.017, hazard ratio (HR) =0.785) and overall survival (
P
=0.014, HR=0.707). In particular, the absence of tumour infiltration and necrosis were associated with prognosis.
Conclusion:
The use of NACT resulted in a high rate (80%) of optimal IDS for the treatment of endometrial cancer with transperitoneal spread.
Journal Article
Randomized Trial of Fetal Surgery for Moderate Left Diaphragmatic Hernia
by
Johnson, Anthony
,
Morini, Francesco
,
Benachi, Alexandra
in
Adult
,
Balloon Occlusion - adverse effects
,
Balloon Occlusion - instrumentation
2021
In this randomized trial involving fetuses with moderate left congenital diaphragmatic hernia, fetoscopic endoluminal tracheal occlusion at 30 to 32 weeks of gestation did not significantly increase survival to discharge from a NICU or reduce the need for oxygen supplementation at 6 months, and it increased the risks of preterm, prelabor rupture of membranes and preterm birth. The surgical technique is shown in an animated video.
Journal Article