PubMed Health⌕ Search

Biomedical subjects

L Tabar

Publications and source records attributed to L Tabar.

At least 19 recordsLinked to original sources
PubMed2001

International investigation of breast MRI: results of a multicentre study (11 sites) concerning diagnostic parameters for contrast-enhanced MRI based on 519 histopathologically correlated lesions.

A multicentre study was undertaken to provide fundamentals for improved standardization and optimized interpretation guidelines of dynamic contrast-enhanced MRI. Only patients scheduled for biopsy of a clinical or imaging abnormality were included. They underwent standardized dynamic MRI on Siemens 1.0 (163 valid lesions > or = 5 mm) or 1.5 T (395 valid lesions > or = 5 mm) using 3D fast low-angle shot (FLASH; 87 s) before and five times after standardized bolus of 0.2 mmol Gd-DTPA/kg. One-Tesla and 1.5 T data were analysed separately using a discriminant analysis. Only histologically correlated lesions entered the statistical evaluation. Histopathology and imaging were correlated in retrospect and in open. The best results were achieved by combining up to five wash-in or wash-out parameters. Different weighting of false-negative vs false-positive calls allowed formulation of a statistically based interpretation scheme yielding optimized rules for the highest possible sensitivity (specificity 30%), for moderate (50%) or high (64-71%) specificity. The sensitivities obtained at the above specificity levels were better at 1.0 T (98, 97, or 96%) than at 1.5 T (96, 93, 86%). Using a widely available standardized MR technique definition of statistically founded interpretation rules is possible. Choice of an optimum interpretation rule may vary with the clinical question. Prospective testing remains necessary. Differences of 1.0 and 1.5 T are not statistically significant but may be due to pulse sequences.

Adult↗
PubMed2001

Mammographic screening: international perspective.

The twentieth century saw the introduction of mammography as a diagnostic tool and its refinement as a screening method. It appears guaranteed that women who are well informed will seek mammography screening with high expectations of technical quality and accurate interpretation. More refined knowledge of breast anatomy and pathology will assist radiologists to interpret with high specificity. We will learn how to recognized more accurately normal structures and doubtful findings. We will gain experience in interpretation through faithful review of interval cancers and subtle screen-detected cancers, and will use educational tools that have the potential to improve the efficiency of education by directing attention to specific deficiencies. Mammographic screening has been advanced through the efforts of dedicated teams of physicians, scientists, and other professionals throughout the world. The international communication of ideas and discoveries will continue to challenge the boundaries of what can be accomplished in early detection as well as noninvasive therapy, and this body of knowledge will continue to be enriched by these diverse contributions.

Breast Neoplasms↗
PubMed2000

Author reply

Explore the source record for details and available documents.

Journal Article↗
PubMed2000

Estimation of sojourn time in chronic disease screening without data on interval cases.

Estimation of the sojourn time on the preclinical detectable period in disease screening or transition rates for the natural history of chronic disease usually rely on interval cases (diagnosed between screens). However, to ascertain such cases might be difficult in developing countries due to incomplete registration systems and difficulties in follow-up. To overcome this problem, we propose three Markov models to estimate parameters without using interval cases. A three-state Markov model, a five-state Markov model related to regional lymph node spread, and a five-state Markov model pertaining to tumor size are applied to data on breast cancer screening in female relatives of breast cancer cases in Taiwan. Results based on a three-state Markov model give mean sojourn time (MST) 1.90 (95% CI: 1.18-4.86) years for this high-risk group. Validation of these models on the basis of data on breast cancer screening in the age groups 50-59 and 60-69 years from the Swedish Two-County Trial shows the estimates from a three-state Markov model that does not use interval cases are very close to those from previous Markov models taking interval cancers into account. For the five-state Markov model, a reparameterized procedure using auxiliary information on clinically detected cancers is performed to estimate relevant parameters. A good fit of internal and external validation demonstrates the feasibility of using these models to estimate parameters that have previously required interval cancers. This method can be applied to other screening data in which there are no data on interval cases.

Aged↗
PubMed2000

Potential contribution of computer-aided detection to the sensitivity of screening mammography.

PURPOSE: To determine the false-negative rate in screening mammography, the capability of computer-aided detection (CAD) to identify these missed lesions, and whether or not CAD increases the radiologists' recall rate. MATERIALS AND METHODS: All available screening mammograms that led to the detection of biopsy-proved cancer (n = 1,083) and the most recent corresponding prior mammograms (n = 427) were collected from 13 facilities. Panels of radiologists evaluated the retrospectively visible prior mammograms by means of blinded review. All mammograms were analyzed by a CAD system that marks features associated with cancer. The recall rates of 14 radiologists were prospectively measured before and after installation of the CAD system. RESULTS: At retrospective review, 67% (286 of 427) of screening mammography-detected breast cancers were visible on the prior mammograms. At independent, blinded review by panels of radiologists, 27% (115 of 427) were interpreted as warranting recall on the basis of a statistical evaluation index; and the CAD system correctly marked 77% (89 of 115) of these cases. The original attending radiologists' sensitivity was 79% (427 of [427 + 115]). There was no statistically significant increase in the radiologists' recall rate when comparing the values before (8.3%) with those after (7.6%) installation of the CAD system. CONCLUSION: The original attending radiologists had a false-negative rate of 21% (115 of [427 + 115]). CAD prompting could have potentially helped reduce this false-negative rate by 77% (89 of 115) without an increase in the recall rate.

Adult↗
PubMed2000

Mammographic screening in women with a family history of breast cancer: some results from the Swedish two-county trial.

BACKGROUND: The objective of this study is to compare the effectiveness of mammographic screening in women with a family history of breast cancer to those without. In the invited arm of a randomised trial of breast cancer screening, data on family history of breast cancer were available on 29.179 women aged 40-74 attending for screening. Among those women, 358 were diagnosed with breast cancer during the trial. METHODS: Those with and without a family history were compared with respect to mammographic parenchymal pattern, interval cancer rates, mean sojourn time and sensitivity of screening. In the 358 cancers, the effect of family history was estimated on survival, incidence of advanced cancers and their relationship to screen detection. RESULTS: A significantly higher proportion of high risk mammographic patterns was observed in association with family history among women aged 40-49. Interval cancer rates were higher in women with a family history, and in older women at least, mean sojourn time was shortened in women with a family history (1.89 years compared to 2.70). Survival was better (although not significantly so) in cancers in women with a family history (relative hazard=0.52) independently of detection mode and was significantly poorer in interval cancers then screen detected cancers (relative hazard=2.72) independently of family history. Similarly, interval cancers tended to be larger, and worse malignancy grade in those with and without a family history of breast cancer. CONCLUSIONS: These results suggest that the policy often adopted of annual screening for woman aged 40-49, with a family history of breast cancer, is a reasonable one, and that it may also be necessary to shorten the inter-screening interval to one year in women aged over 50 but with a positive family history.

Adult↗
PubMed2000

Some random-effects models for the analysis of matched-cluster randomised trials: application to the Swedish two-county trial of breast-cancer screening.

BACKGROUND: In the Swedish two-county trial women aged 40-74 years from two counties in Sweden were randomised to invitation to mammographic screening for breast cancer. METHODS: This paper uses random effects logistic regression models to analyse recent data from the trial. The analysis accounts for the structure of the trial, where small geographical units are randomised within larger geographical strata (blocks of two or three small units that are socio-economically similar). RESULTS: Fixed effects and a variety of random effects models show a strong degree of agreement and yield a significant 29% or 30% reduction in breast-cancer mortality. DISCUSSION: Fixed effects and random effects models agree for this example, because heterogeneity both between strata and within strata between clusters is small and because the effect of treatment does not vary much in different strata.

Adult↗
PubMed1999

Update of the Swedish Two-County Trial of breast cancer screening: histologic grade-specific and age-specific results.

UNLABELLED: The benefit of mammographic screening in reducing mortality from breast cancer is well established. Questions remain with respect to the magnitude of the long-term benefit of modern mammography screening, age specific benefits and the timing of these, and histology specific effects. METHODS: The Swedish Two-County Trial was set up in 1977, with 77,080 women aged 40-74 randomised to invitation to mammographic screening for breast cancer (active study population, ASP) and 55,985 women randomised to no invitation (passive study population, PSP). There is now follow-up for mortality to 31 December 1996, approximately 18 years average follow-up. We investigated the effect of invitation of screening on breast cancer mortality and incidence of advanced tumours by age group (40-49 and 50-74) and histologic type. In addition we estimated progression rates by histologic grade using markov chain models. RESULTS: A significant 29% reduction in breast cancer mortality was observed in association with invitation to screening (relative risk = 0.71, 95% confidence interval 0.60-0.83), maintaining the effect observed at previous stages of follow-up. Age-specific analyses show a smaller and later mortality benefit in women aged 40-49. This is related to the fact that there is a considerable benefit from early detection in terms of mortality from aggressive, poorly differentiated cancers in women aged 50-74, whereas the major effect in women aged 40-49 is on the less aggressive tumours of good or intermediate differentiation. Among women aged 50-74, the incidence of grade III tumours in the ASP is significantly lower than in the PSP, but this is not the case for women aged 40-49. This is related to the greater prevalence and rapidity of progression with respect to histologic grade, as evidenced by the results of markov chain models and the proportions of grade III tumours by time since last screen. CONCLUSIONS: The substantial and significant mortality benefit of invitation to mammographic screening in women aged 40-74 is maintained at 18 years of follow-up. To achieve a substantial mortality benefit at an early stage in the screening program in women aged under 50 years, an interscreening interval of 12-18 months would be required.

Adult↗
PubMed1999

Primary and adjuvant therapy, prognostic factors and survival in 1053 breast cancers diagnosed in a trial of mammography screening.

BACKGROUND: As mammographic screening becomes more widespread, larger numbers of tumours are diagnosed while small and node negative. METHODS: We examined detection mode, tumour size, node status, histological type, therapy and outcome in 1053 breast cancers diagnosed in one county of the Swedish Two-County Trial of mammographic screening for breast cancer. RESULTS: Of patients undergoing total mastectomy with axillary dissection, 65% were found to be node negative. For tumours of size 1-9 mm, 95% were node negative. The major effects on survival were tumour size, node status and histological type. Primary adjuvant therapy had no significant association with survival. CONCLUSIONS: The advent of mammography has substantially enhanced the possibilities for less radical treatment. There is an urgent need for therapeutic trials utilizing mammographic-pathological correlations to ascertain in advance which tumours can and which cannot benefit from more radical therapy.

Adult↗
PubMed1999

Moderate physical activity in relation to mammographic patterns.

High-risk mammographic patterns may be used as a surrogate end point for breast cancer in etiologic research as well as in prevention studies. Physical activity may be one of the few modifiable risk factors for breast cancer. We examined the relationship between physical activity and mammographic patterns among 2720 Norwegian women, ages 40-56 years, who participated in both the Second and Third Tromsø studies. Epidemiologic data were obtained through questionnaires. Two questions from the Second Tromsø study and five questions from the Third elicited information on physical activity. The mammograms were categorized into five groups based on anatomical-mammographic correlations. For analysis, patterns I through III were combined into a low-risk group and patterns IV and V into a high-risk group. Odds ratios that were adjusted for age, education, menopausal status, body mass index, parity, age at menarche, oral contraceptive use, and alcohol intake, with 95% confidence intervals, were estimated using logistic regression. Women who reported moderate physical activity, i.e., more than 2 h/week, were 20% less likely (odds ratio, 0.8; 95% confidence interval, 0.6-1.1) to have high-risk mammographic patterns compared with those who reported being inactive. This relationship remains consistent when stratified by menopausal status, parity, and tertiles of body mass index. However, all of the associations between various measures of physical activity and high-risk patterns found in this study are weak with confidence intervals that include 1.0. Thus, chance is a reasonable explanation for the weak associations found. The relationship between physical activity and high-risk patterns should be examined further as a means to explore the biologic mechanisms relating physical activity to breast cancer risk.

Adult↗
PubMed1998

Evaluation by Markov chain models of a non-randomised breast cancer screening programme in women aged under 50 years in Sweden.

STUDY OBJECTIVE: To apply Markov chain models that have previously been used on data in randomised trials of breast cancer screening to data from an uncontrolled service screening programme; to compare results with those from a randomised trial. DESIGN: A service screening programme in Uppsala county, Sweden, inviting 25,660 women aged 39-49 to mammographic screening every 20 months, and the Swedish Two-County Trial inviting 19,844 women aged 40-49 to two yearly screening, compared with 15,604 women of the same age in an unscreened control group. Data were analysed using Markov chain models and quasi-likelihood estimation procedures. MAIN RESULTS: The results with respect to parameters of disease progression were very similar between the two studies. Use of estimated progression rates to predict the effect on mortality ranged from a 10% to a 17% reduction in breast cancer mortality in the Two-County Study and predicted a 15% reduction in the Uppsala programme. These compare well with the observed mortality reduction of 13% in the Two-County Trial. CONCLUSIONS: The screening in the Uppsala programme is likely to have a similar effect to that observed in the Two-County Trial. It is feasible to evaluate non-randomised service screening programmes using Markov chain models.

Adult↗
PubMed1997

Anthropometric indices in relation to mammographic patterns among peri-menopausal women.

The relationship between body height, weight and body mass index and mammographic patterns was examined among 3,208 Norwegian women, aged 40-56 years, participating in the Third Tromsø study. Standardized measurements of height and weight were recorded. Epidemiologic data were obtained through questionnaires. Mammograms were categorized into 5 groups based on anatomic-mammographic correlations. For analysis, patterns I-III were combined into a low-risk group and patterns IV and V into a high-risk group. Odd ratios (ORs), adjusted for menopausal status, age, parity, age at first birth, age at menarche and anthropometric measures, with 95% confidence intervals (CIs), were calculated. Body height was associated positively with high-risk patterns, while weight and body mass index were associated inversely with high-risk patterns. Women in the highest tertile of height were twice as likely (OR = 2.0, 95% CI 1.6-2.6) to have high-risk patterns compared with those in the lowest tertile, and women in the highest tertile of weight were 70% less likely (OR = 0.3, 95% CI 0.2-0.4) to have high-risk patterns compared with those in the lowest tertile. Associations with body mass index were similar to those with weight. All associations were present when stratified by menopausal status. Among post-menopausal women, the inverse associations between body weight and body mass index and high-risk patterns decreased with increasing number of years since menopause. Our results indicate that body height and weight are independently associated with the mammographic pattern among peri-menopausal women. We suggest that body height and weight are related to mammographic patterns through different mechanisms.

Adult↗
PubMed1996

Tumour development, histology and grade of breast cancers: prognosis and progression.

Using 1,973 breast tumours from women aged 40-69 participating in the Swedish two-county trial of mammographic screening for breast cancer, we examined the effect of histological type on prognosis and sojourn time (the duration of the preclinical screen-detectable phase) by age. The hypothesis of dedifferentiation, according to which a cancer of mixed malignancy grade drifts towards grade 3 as the more poorly differentiated part of the tumour grows faster than the well-differentiated part, was also assessed. Ductal carcinoma in situ, invasive ductal carcinoma of grade 1, mucinous carcinoma and tubular carcinoma were all associated with good survival. Ductal carcinoma of grade 3 was associated with poor survival. Ductal carcinoma of grade 2, lobular and medullary carcinoma were associated with intermediate survival. These patterns were much the same in women aged 40-49 as in women aged 50-69. In women aged 40-49, sojourn time was estimated at about 2 years regardless of histological type. For women aged 50-69, there was a marked association of sojourn time with histological type, the shortest sojourn time being observed for lobular (2 years) and medullary (1.2 years) carcinoma, and the longest for ductal carcinoma grade 1 (7.7 years) and tubular carcinoma (7.1 years). There was strong evidence of a potential to dedifferentiation. A mover-stayer mixture of Markov chain models estimated that, in women aged 40-54, 91% of ductal tumours have the potential to dedifferentiate and, in women aged 55-69, 38% of ductal tumours have such a potential.

Adult↗
PubMed1996

Sojourn time, sensitivity and positive predictive value of mammography screening for breast cancer in women aged 40-49.

BACKGROUND: In mammographic screening for breast cancer in women aged 40-49, previous studies have found very low estimates of sensitivity and predictive value. Methods of estimation have, however, used primitive models with relatively strong assumptions and less than full use of the data. METHODS: Here we estimate the underlying preclinical incidence, mean sojourn time, sensitivity and positive predictive value by a variety of methods in a randomized trial of mammographic screening (The Swedish Two-County Trial) and a service screening programme (The Florence Programme, 1975-1986) in women aged 40-49 years. RESULTS: In the Two-County study, sensitivity estimates ranged from 72-83% and predictive value from 39-89%. In the Florence programme, sensitivity estimates ranged from 69-85% and predictive value was uniformly estimated as 100%. CONCLUSIONS: The methods involving more explicit modelling of the disease process and fewer assumptions tended to find higher estimates of predictive value in the Two-County study. The results suggest that previously poor sensitivity and predictive value estimates may have been overpessimistic.

Adult↗
PubMed1996

An overview of the Swedish randomised mammography trials: total mortality pattern and the representivity of the study cohorts.

OBJECTIVES: To analyse the cause of death pattern in the cohorts of women included in the Swedish randomised mammography screening trials by comparing the groups of invited and control women both with each other and with the general population of Swedish women. SETTING: Since 1977 four randomised trials of mammography screening have been performed in Sweden: Malmö, Kopparberg and Ostergötland (the two county trial), Stockholm, and Gothenburg. DESIGN: Overview of four randomised mammography screening trials. RESULTS: The total numbers of deaths in the invited and control groups respectively were 15 695 and 11 887 corresponding to a relative risk (RR) of 1.00. There were no significant differences between the invited and control groups for cause-specific mortality, except for breast cancer. When the total mortality in the invited and the control groups was compared with that for Swedish women in general the standardised mortality ratio was close to 100. CONCLUSIONS: The cause of death pattern in the invited group was, except for breast cancer, very similar to that in the control group, showing that the groups were comparable. Similarly, the total mortality including breast cancer mortality in the control group was almost identical to that in Swedish women in general. The same was true, with the exception of breast cancer, for the invited group. These observations confirm that the trial cohorts are representative of Swedish women and indicate that the quantitative results from these trials may safely be generalised to the Swedish populations.

Adult↗