Extended follow-up of the Multicentre Aneurysm Screening Study (MASS)

Lead Research Organisation: MRC Biostatistics Unit

Abstract

An aneurysm is a weakness of the wall of an artery leading to localised ballooning of that blood vessel. The commonest site is in the abdomen, hence the name ?abdominal aortic aneurysm? or AAA. In the few people with a large AAA, there is a risk of serious problems if the condition remains undetected as the artery could rupture, often without warning; about 7000 people die from this condition every year in the UK. The condition usually occurs as people get older, and is more common in men than women. The reasons why some people develop AAAs and why AAAs expand at different rates are unclear. AAAs are difficult to feel on routine examination by doctors, but can be easily, quickly and painlessly identified using ultrasound. If an AAA is found, the treatment will depend on its size. Small AAAs rarely cause problems but they do tend to slowly increase in size, and so need to be monitored. Should the AAA expand significantly, a vascular surgeon will assess the patient and decide whether surgery is indicated. The procedure involves the artery being strengthened with a tube, usually made of woven polyester. This is a major operation and, like any other operation, does carry some risks to the patient. Our work shows that through early detection and treatment, the mortality from AAAs can be halved. Continued follow-up of the large population of 67,800 men already involved in the MASS study should allow us to find out how long the benefit lasts, and to see if a single scan is sufficient to identify those at risk from the condition in the future. The UK National Screening Committee recommended a national AAA screening programme for men at age 65 to the government in February 2006. So we will be able to provide information for the programme?s implementation and development, based on high quality long-term data on the benefits and costs of screening and treatment.

Technical Summary

The Multicentre Aneurysm Screening Study (MASS) was set up as a randomised control trial to assess: (1) the effect of screening using ultrasonography on the mortality from ruptured abdominal aortic aneurysms (AAA), (2) the quality of life of those recruited to a screening programme, and (3) costs to the NHS. A population-based sample of 67,800 men aged 65-74 were randomised to either invitation to screening or control. The initial results at four years of follow-up have been published, showing: (1) The invited group had a 42% reduction (95% CI 22% to 58%) in AAA-related mortality compared to the control group; (2) Screening did not have any major psychological impact on patients; (3) Even at four years the estimated cost-effectiveness of screening for AAA was at the margin of acceptability according to current NHS thresholds. Results of a mid-term analysis at seven years of follow-up are to be published shortly, which support the earlier findings. However, some important questions remain concerning the longer-term benefits of AAA screening, and MASS is uniquely poised to answer these. We propose to extend follow-up to 13 years, to allow continued monitoring of AAA surgery, AAA-related and all-cause mortality. As all subjects have been previously tagged for mortality surveillance at the Office of National Statistics through their NHS numbers, systems are in place for obtaining copies of death certificates and entering and analysing the data. Experienced staff are in post to manage the office databases and extract data from hospital records, patient notes and information systems. Should the collection of surgical and mortality data not continue, expertise and systems set up by the present screening programme would be lost and difficult to retrieve at a later date. An extension to follow-up will enable us to provide estimates, from directly observed data, of the long-term effectiveness and cost-effectiveness of AAA screening, as well as the incidence of aortic rupture in those with an initially normal scan.
 
Description Impact on UK national AAA screening programme
Geographic Reach Asia 
Policy Influence Type Citation in other policy documents
Impact Helped to develop the basis for the UK National AAA screening programme. High profile paper in BMJ (PMID: 19553269) with associated press coverage
URL http://europepmc.org/abstract/MED/19553269
 
Description Invited participant at UK National Screening Committee Working Group on abdominal aneurysm screening, London.
Geographic Reach Asia 
Policy Influence Type Participation in advisory committee
Impact Invited participant at UK National Screening Committee Working Group on abdominal aneurysm screening, London. ; UK national screening programme initiated
 
Guideline Title Screening for Abdominal Aortic Aneurysm: Recommendation Statement
Description Recommendation for AAA screening
Geographic Reach Multiple continents/international 
Policy Influence Type Citation in clinical guidelines
Impact International recognition of the value of national systematic screening programmes for AAA; Initiation of UK national screening programme
URL http://annals.org/article.aspx?articleid=718158
 
Title Cost-effectiveness Analysis 
Description Novel methods for undertaking cost-effectiveness analysis based on cause specific mortality to increase precision of estimates 
Type Of Material Technology assay or reagent 
Year Produced 2008 
Provided To Others? Yes  
Impact Improved methodology which is generally applicable 
 
Title Validation of long term health economic models 
Description PMID 19206080 
Type Of Material Technology assay or reagent 
Year Produced 2009 
Provided To Others? Yes  
Impact Appreciation of the problems of validating long term health economic models 
URL http://europepmc.org/abstract/MED/19206080
 
Description Extended follow-up of the MASS Randomised Trial of Aortic Aneurysm Screening 
Organisation St Richard's Hospital
Department Scott Research Unit
Country United Kingdom 
Sector Hospitals 
PI Contribution Statistical responsibility for the MASS Trial
Collaborator Contribution Coordination and management of the MASS Trial
Impact Publications
 
Description Abdominal aortic aneurysms: from randomised trials to a national screening policy 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Health professionals
Results and Impact Invited speaker at NICE workshop: Evidence Synthesis and Public Health: "Abdominal aortic aneurysms: from randomised trials to a national screening policy".

Recognition for the MRC and the Unit
Year(s) Of Engagement Activity 2008
 
Description Addenbrookes Biomedical Research Centre Open Day 
Form Of Engagement Activity Participation in an open day or visit at my research institution
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Public/other audiences
Results and Impact About hundred people attended talks and discussed posters

Networking
Year(s) Of Engagement Activity 2009
 
Description Cambridge Science Festival 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? Yes
Geographic Reach Regional
Primary Audience Schools
Results and Impact Helped man the Unit's display for Cambridge Science Festival

Raised awareness of the Unit's work in the local schools community
Year(s) Of Engagement Activity 2007,2008,2009,2011
 
Description Cambridge Science Festival 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? Yes
Type Of Presentation Workshop Facilitator
Geographic Reach Regional
Primary Audience Schools
Results and Impact Helped man the Unit's display for the festival

Raised awareness of the work of the Unit in the local school community
Year(s) Of Engagement Activity 2007,2008,2009,2010,2011
 
Description Quintessential 'Counting for Health' 
Form Of Engagement Activity A formal working group, expert panel or dialogue
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Policymakers/politicians
Results and Impact Policy relevant topical examples in 'Counting for Health' were used to illustrate how cost-effectiveness is worked out for screening programmes

Recognition for the MRC and the Unit
Year(s) Of Engagement Activity 2009