Abstract
This study answers the question: 'How far must a Canadian woman travel before the risk of a motor vehicle accident (MVA) outweighs the benefits of mammography screening?'. Numbers needed to screen and false positive rates were extracted from information in the breast screening guidelines from the Canadian Task Force on screening for breast cancer. Motor vehicle accidents per billion vehicle kilometres were extracted from Transport Canada. The charts of women undergoing screening mammograms were reviewed to determine the average number of extra trips generated from a false positive mammogram. A formula was devised to determine when the distance travelled and risk of MVA outweighed the benefits of mammogram screening. How far a woman would need travel before the risk of that travel outweighed the benefits of screening mammography is determined by the province in which she lives (location) and her age. The distance of a round trip before the risk of travel outweighed the benefit of screening mammography varied from 65 km to 1151 km, according the patient's age and location. Travel risk is rarely discussed in recommending screening examinations. Nevertheless the benefits of screening can be outweighed by the risk of travel. Knowledge of travel risk is essential before recommending screening procedures.
Highlights
This study answers the question: ‘How far must a Canadian woman travel before the risk of a motor vehicle accident (MVA) outweighs the benefits of mammography screening?’
A formula was devised by the authors to determine when the risks of round trip to a screening site outweighed the benefits of screening mammography
According to the Canadian Task Force on Preventive Health Care, the number needed to screen for mammography over 11 years is 2108 for women aged 40-49 years, with a false positive rate of 32.9%, 720 for women aged 50-69 with a false positive rate of 28 %, and 450 for women aged 70-74 with a false positive rate of 21%6
Summary
Mammography is a controversial screening tool[1,2,3,4]. As with any screening program, the benefits of lives saved must be balanced against the risk of harm to the patient. One overlooked risk is the danger of travel to the screening site, in large nations such as Canada. While the costs of travel in both accidents and dollar amount has been raised[5], no literature was found that assessed the risk of injury or death from road travel and its effect on the risk–benefit profile of screening mammography. This article asks 'How far is too far?', before the risk of death or injury on the road outweighs the benefit of screening mammography
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