Biomedical subjects
Publications and source records attributed to Michael R Thompson.
Bowel cancer is a major cause of morbidity and death and is a high cost to health care systems. Screening currently offers the best chance of improving outcomes from bowel cancer. When introducing screening, the problems encountered in other cancers need to be avoided to maximize benefits and minimize harms.
PURPOSE: This study was designed to develop a model for predicting postoperative mortality in elderly patients undergoing surgery for colorectal cancer. METHODS: This multicenter study was conducted by using routinely collected clinical data, assessing patients older than aged 80 years, with 30-day operative mortality as the primary end point. Data were collected from The Association of Coloproctology of Great Britain and Ireland database, encompassing 8,077 newly diagnosed colorectal cancer patients undergoing resectional surgery in 79 hospitals between April 2000 to March 2002, The Association of Coloproctology Malignant Bowel Obstruction Study, encompassing 1,046 patients with malignant bowel obstruction in 148 hospitals, between April 1998 to March 1999, and The Wales-Trent audit, encompassing 3,522 newly diagnosed colorectal cancer patients, between July 1992 to June 1993. A multilevel logistic regression model was developed to adjust for case-mix and to accommodate the variability of outcomes between the three study populations. The model was internally validated using a Bayesian resampling technique and tested using measures of discrimination, calibration, and subgroup analysis. RESULTS: A total of 2,533 patients satisfied the inclusion criteria, with a 30-day mortality of 15.6 percent. Multivariate analysis identified the following independent risk factors: age (odds ratio for 85-90, 90-95, >95 vs. 80-85 = 1.1, 1.8, 2.9), American Society of Anesthesiology grade (odds ratio for Grade III, IV vs. I-II = 2.7, 6.1), operative urgency (odds ratio for emergency vs. elective = 1.9), no cancer excision vs. resection (odds ratio = 1.2), and metastatic disease (odds ratio for metastases vs. no metastases = 1.9). The model offered adequate discrimination (area under receiver operator curve = 0.732) and excellent agreement between observed and predicted outcomes during eight colorectal procedures (P = 0.885). CONCLUSIONS: The elderly colorectal cancer model can accurately estimate 30-day mortality in patients older than aged 80 years undergoing surgery for colorectal cancer. Because the mortality can be considerable, this may have important implications when determining management for this group of patients.
PURPOSE: This study was designed to develop a mathematical model for predicting the number of lymph nodes harvested in bowel cancer resection specimens based on the current clinical practice in the United Kingdom. METHODS: Prospective clinical data were collected from 8,409 newly diagnosed bowel cancer patients presenting to 79 hospitals in Great Britain and Ireland during a variable 12-month period from 2000 to 2002. A two-level hierarchical regression model was used to identify predictors for lymph node harvest. The model was internally validated by comparing observed and model predicted lymph node harvest for patient subgroups. RESULTS: Inclusion criteria were satisfied by 5,164 patients. The average lymph node harvest was 11.7 nodes with significant between-center variability in lymph node harvest (range, 5.5-21.3 nodes). Increasing age, American Society of Anesthesiology grade, and preoperative radiotherapy were associated with a reduction of lymph node harvest (P < 0.001). Abdominoperineal resection of the rectum and transverse colectomy were the lowest yield procedures for lymph node harvest. Independent predictors of lymph node harvest were age, American Society of Anesthesiology grade, Dukes stage, operative urgency, type of resection, and preoperative radiotherapy. When tested, the model was found to accurately predict lymph node harvest for group statistics (comparison of observed and model predicted lymph node harvest F(1,5154) = 0.63; P = 0.427). CONCLUSIONS: The results of the study suggest that the minimum number of lymph nodes harvested in colorectal cancer surgery cannot be set at a fixed value. The lymph node harvest model provides a simple tool to the frontline clinician for comparing standards between multidisciplinary bowel cancer teams.
BACKGROUND: Rectal bleeding is a common symptom. The ability to distinguish those patients having serious underlying pathology from those with self-limiting conditions is a continuing dilemma in general practice. AIM: To determine the factors affecting the predictive and diagnostic value of rectal bleeding for bowel cancer in primary care. DESIGN OF STUDY: One-year prospective observational study. SETTING: Three large general practices. METHOD: Three hundred and nineteen consecutive patients over the age of 34 years consulting their GPs with rectal bleeding were included in the study. Investigation was by flexible sigmoidoscopy or a questionnaire and review of all patients took place after 18 months. The main outcome measures were consultation rates; the prevalence of cancer, colitis and significant polyps in patients presenting with rectal bleeding; its diagnostic value when occurring with or without a change in bowel habit, perianal symptoms and abdominal pain. RESULTS: The consultation rate for rectal bleeding in patients over the age of 34 years was 15 per 1000 per year; 3.4% had colorectal cancer. The prevalence of cancer increased to 9.2% when the rectal bleeding was associated with a change in bowel habit, and to 11.1% when it was without perianal symptoms. Thirty-six per cent of cancer patients had a palpable rectal mass. CONCLUSION: Over 96% of the patients who present to their GPs with rectal bleeding do not have cancer. Greater awareness of the diagnostic value of the different symptom combinations of rectal bleeding could help GPs adopt different management strategies for patients at higher and very low risk of cancer.
BACKGROUND: This study was designed to investigate the early outcomes after surgical treatment of malignant large bowel obstruction (MBO) and to identify risk factors affecting operative mortality. METHODS: Data were prospectively collected from 1046 patients with MBO by 294 surgeons in 148 UK hospitals during a 12-month period from April 1998. A predictive model of in-hospital mortality was developed using a 3-level Bayesian logistic regression analysis. RESULTS: The median age of patients was 73 years (interquartile range 64-80). Of the 989 patients having surgery, 91.7% underwent bowel resection with an overall mortality of 15.7%. The multilevel model used the following independent risk factors to predict mortality: age (odds ratio [OR] 1.85 per 10 year increase), American Society of Anesthesiologists grade (OR for American Society of Anesthesiologists grade I versus II,III,IV-V = 3.3,11.7,22.2), Dukes' staging (OR for Dukes' A versus B,C,D = 2.0, 2.1, 6.0), and mode of surgery (OR for scheduled versus urgent, emergency = 1.6, 2.3). A significant interhospital variability in operative mortality was evident with increasing age (variance = 0.004, SE = 0.001, P < 0.001). No detectable caseload effect was demonstrated between specialist colorectal and other general surgeons. CONCLUSIONS: Using prognostic models, it was possible to develop a risk-stratification index that accurately predicted survival in patients presenting with malignant large bowel obstruction. The methodology and model for risk adjusted survival can set the reference point for more accurate and reliable comparative analysis and be used as an adjunct to the process of informed consent.
OBJECTIVE: To develop a mathematical model that will predict the probability of death after surgery for colorectal cancer. DESIGN: Descriptive study using routinely collected clinical data. DATA SOURCE: The database of the Association of Coloproctology of Great Britain and Ireland (ACPGBI), encompassing 8077 patients with a new diagnosis of colorectal cancer in 73 hospitals during a 12 month period. STATISTICAL ANALYSIS: A three level hierarchical logistic regression model was used to identify independent predictors of operative mortality. The model was developed on 60% of the patient population and its validity tested on the remaining 40%. RESULTS: Overall postoperative mortality was 7.5% (95% confidence interval 6.9% to 8.1%). Independent predictors of death were age, American Society of Anesthesiology (ASA) grade, Dukes's stage, urgency of the operation, and cancer excision. When tested the predictive model showed good discrimination (area under the receiver operating characteristic curve = (0.775) and calibration (comparison of observed with expected mortality across different procedures; Hosmer-Lemeshow statistic = 6.34, 8 df, P = 0.610). CONCLUSIONS: Clinicians can predict postoperative death by using a simple numerical table derived from the statistical model of the ACPGBI. The model can be used in everyday practice for preoperative counselling of patients and their carers as a part of multidisciplinary care. It may also be used to compare the outcomes between multidisciplinary teams for colorectal cancer.
An improved functional approach for designing MRI (magnetic resonance imaging) main magnets with active shielding is presented. By nulling one or two external moments as well as a certain series of internal moments of the magnetic field, new designs with improved shielding in combination with or without shorter magnet lengths are obtained. The improved method can be employed to design short and practical superconducting magnets at any given field strength. The resulting designs yield the desired field homogeneity inside the region of interest without using superconducting shim coils. This approach requires only a modest amount of computing power. One of the design steps, a contour plot of the continuous current solutions, can be utilized to study stretch goals for favorable design parameters.