Patient Outcomes From Second Film-readers and Test Threshold Relaxation in Breast Screening

Study Overview
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Brief Summary
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Analysis of women's medical records to understand the impact of previous changes to breast cancer screening (increase from one to two clinicians examining each woman's mammograms, and what proportion of women they recall for further tests)

Detailed Description
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Retrospective observational study examining the records and outcomes of women who attended breast cancer screening between 1988 and 2016. Linkage of records from the breast screening service, the cancer registry, and mortality. Analysis of whether changing the threshold for whether to recall women for further tests or the number of clinicians examining the mammograms for signs of cancer affects outcomes.

Official Title
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Patient Outcomes From Second Film-readers and Test Threshold Relaxation in Breast Screening: An Observational Retrospective Cohort Study

Conditions
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Breast Cancer, Ductal Carcinoma in Situ

Intervention / Treatment
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* Diagnostic Test: Breast Screening Mammography with single reader
* Diagnostic Test: Breast screening mammography with two readers
* Diagnostic Test: Test threshold


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Women who attended the English National Health Service (NHS) breast cancer screening service at least once between 1988 and 2016, aged between 47 and 73 All eligible episodes of screening for each woman (we expect women to be screened around 7 times each) Exclusion Criteria: Women who did not attend routine English NHS Breast screening service within the specified date and age range, even if they attended symptomatic breast cancer services, high risk (family history) breast screening services, or if they were referred for mammograms by their general practitioner

Ages Eligible for Study
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Minimum Age: 47 Years
Maximum Age: 73 Years

Sexes Eligible for Study
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Female

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Single reading<br>Only one clinician examined the woman's mammograms for signs of cancer and recommended whether to recall her for further tests or not. | Diagnostic Test: Breast Screening Mammography with single reader<br>* One clinician examined each woman's mammograms for signs of cancer<br>Diagnostic Test: Test threshold<br>* Threshold used by readers examining the breast screening mammograms, defined using their previous proportion of cases recalled<br>|
| Double reading<br>Two clinicians examined the woman's mammograms for signs of cancer and recommended whether to recall her for further tests or not. | Diagnostic Test: Breast screening mammography with two readers<br>* Two clinicians seperately examined each woman's mammograms for signs of cancer<br>Diagnostic Test: Test threshold<br>* Threshold used by readers examining the breast screening mammograms, defined using their previous proportion of cases recalled<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Number of women overdiagnosed (the cancer would not have become symptomatic within the woman's lifetime) using compensatory drop method | Overdiagnosis of breast cancer (measured as difference in total cancer incidence, screen and symptomatic). Will also report mechanism of action (number of screen detected cancers, number of symptomatically detected cancers at 3,13, and 30 years follow-up) | 13 years, and up to 30 years | 
| Cancers detected at screening | Biopsy proven cancers detected at screening | 1 day screening episode | 
| False positive recalls | Recall of women for further tests after screening which did not result in detection of cancer | 1 day screening episode | 
| Breast cancer mortality | Mortality due to breast cancer (dependent on securing follow-on funding) | 13 years, and up to 30 years | 
| All cause mortality | Mortality due to any cause (dependent on securing follow on funding) | 13 years, and up to 30 years | 
| Characteristics of cancer detected | Size, grade and stage (reported overall, screen detected, and symptomatic detected). | 1 day screening episode, 3year, 13 year and up to 30 year follow up | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Breast cancer morbidity | Treatment received as a proxy for treatment associated morbidity (reported overall, screen detected and symptomatically detected, if follow on funding obtained) | Up to 30 years | 
| Breast cancer free survival | Survival without a diagnosis of breast cancer | Up to 30 years follow-up |