Browsing by Subject "Colorectal neoplasia"

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    A two-phase approach to re-calibrating expensive computer simulation for sex-specific colorectal neoplasia development modeling
    (Springer, 2022-09-18) Vivas-Valencia , Carolina; Zhou, You; Sai , Aditya; Imperiale , Thomas F.; Kong , Nan; Medicine, School of Medicine
    Background Medical evidence from more recent observational studies may significantly alter our understanding of disease incidence and progression, and would require recalibration of existing computational and predictive disease models. However, it is often challenging to perform recalibration when there are a large number of model parameters to be estimated. Moreover, comparing the fitting performances of candidate parameter designs can be difficult due to significant variation in simulated outcomes under limited computational budget and long runtime, even for one simulation replication. Methods We developed a two-phase recalibration procedure. As a proof-of-the-concept study, we verified the procedure in the context of sex-specific colorectal neoplasia development. We considered two individual-based state-transition stochastic simulation models, estimating model parameters that govern colorectal adenoma occurrence and its growth through three preclinical states: non-advanced precancerous polyp, advanced precancerous polyp, and cancerous polyp. For the calibration, we used a weighted-sum-squared error between three prevalence values reported in the literature and the corresponding simulation outcomes. In phase 1 of the calibration procedure, we first extracted the baseline parameter design from relevant studies on the same model. We then performed sampling-based searches within a proper range around the baseline design to identify the initial set of good candidate designs. In phase 2, we performed local search (e.g., the Nelder-Mead algorithm), starting from the candidate designs identified at the end of phase 1. Further, we investigated the efficiency of exploring dimensions of the parameter space sequentially based on our prior knowledge of the system dynamics. Results The efficiency of our two-phase re-calibration procedure was first investigated with CMOST, a relatively inexpensive computational model. It was then further verified with the V/NCS model, which is much more expensive. Overall, our two-phase procedure showed a better goodness-of-fit than the straightforward employment of the Nelder-Mead algorithm, when only a limited number of simulation replications were allowed. In addition, in phase 2, performing local search along parameter space dimensions sequentially was more efficient than performing the search over all dimensions concurrently. Conclusion The proposed two-phase re-calibration procedure is efficient at estimating parameters of computationally expensive stochastic dynamic disease models.
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    Changes in Adult BMI and Waist Circumference Are Associated with Increased Risk of Advanced Colorectal Neoplasia
    (Springer, 2017-11) Gathirua-Mwangi, Wambui G.; Monahan, Patrick; Song, Yiqing; Zollinger, Terrell W.; Champion, Victoria L.; Stump, Timothy E.; Imperiale, Thomas F.; Epidemiology, School of Public Health
    BACKGROUND: Waist circumference (WC) is a stronger predictor of colon cancer (CRC) risk than body mass index (BMI). However, how well change in either WC or BMI predicts risk of advanced colorectal neoplasia (AN) is unclear. AIMS: To determine the relationship between change in BMI and WC from early adulthood to later age and the risk of AN and which change measure is a stronger predictor. METHODS: In 4500 adults, ages 50-80, with no previous neoplasia and undergoing screening colonoscopy, BMI and WC at age 21 and at time of screening were reported. Changes in BMI and WC were defined using universal risk cutoffs. Known CRC risk factors were controlled in the logistic models. RESULTS: Overall, model statistics showed WC change (omnibus test χ 2 = 10.15, 2 DF, p value = 0.006) was a statistically stronger predictor of AN than BMI change (omnibus test χ 2 = 5.66, 5 DF, p value = 0.34). Independent of BMI change, participants who increased WC (OR 1.44; 95% CI 1.05-1.96) or maintained a high-risk WC (OR 2.50; 95% CI 1.38-4.53) at age 21 and at screening had an increased risk of AN compared to those with a low-risk WC. Study participants who were obese at age 21 and at screening had an increased risk of AN (OR 1.87; 95% CI 1.08-3.23) compared to those who maintained a healthy BMI. Maintaining an overweight BMI or increasing BMI was not associated with AN. CONCLUSIONS: Maintaining an unhealthy BMI and WC throughout adult life may increase risk of AN. WC change may be a better predictor of AN than BMI change.
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    Long-Term Follow-Up of Colonoscopy Quality Monitoring
    (Wolters Kluwer, 2023-09-01) Patel, Feenalie; Dilly, Christen; Fayad, Nabil; Marri, Smitha; Eckert, George J.; Kahi, Charles; Medicine, School of Medicine
    Introduction: High-quality colonoscopy is paramount for colorectal cancer prevention. Since 2009, endoscopists at our institution have received quarterly report cards summarizing individual colonoscopy quality indicators. We have previously shown that implementing this intervention was associated with short-term improvement in adenoma detection rate (ADR). However, the long-term effect of continued monitoring on colonoscopy quality is unclear. Methods: We conducted a retrospective study of prospectively administered quarterly colonoscopy quality report cards at the Roudebush Veteran's Affairs Medical Center between April 1, 2012, and August 31, 2019. The anonymized reports included individual endoscopists' ADRs, cecal intubation rates, and withdrawal times. Analyses were performed to determine slopes over time for each quality metric by physician and assess for differences based on whether ADRs were calculated quarterly or yearly. Results: Data from the report cards of 17 endoscopists who had performed 24,361 colonoscopies were included. The mean quarterly ADR (±SD) was 51.7% (±11.7%) and mean yearly ADR was 47.2% (±13.8%). There was a small increase in overall ADR based on quarterly and yearly measurements (slope + 0.6%, P = 0.02; and slope +2.7%, P < 0.001, respectively), but no significant change in individual ADRs, cecal intubation rates, or withdrawal times. Analysis of SD of ADRs showed no significant difference between yearly and quarterly measurements ( P = 0.064). Individual endoscopists' ADR SD differences between yearly and quarterly measurements ranged from -4.7% to +6.8%. Discussion: Long-term colonoscopy quality monitoring paralleled stable improvements in overall ADR. For endoscopists with baseline high ADR, frequent monitoring and reporting of colonoscopy quality metrics may not be necessary.