Screening Mammography: A reassessment

Screening mammography, a technique which is 50 years old, aims to advance the diagnosis of breast cancer in order to offer early treatment, thereby improving the chances of cure. The prac- tice of mammography, in constant evolution, varies widely according to the equipment used, the interpretation of films, and program aspects such as the age of women when they are invited to their first screen, the interval between rounds of screening and participation rates.

In 1990, a report by Québec's Conseil d’évaluation des technologies de la santé (CETS) recom- mended that this practice be structured as part of a formal program which would include quality standards. A second CETS report published in 1993 underlined the absence of proof in favour of screening women younger than 50. Since 1998, the Programme québécois de dépistage du cancer du sein (PQDCS) offers systematic screening every 2 years to all women aged 50 to 69. Younger women can still obtain mammography with a prescription from their physicians.

In this context, the ministère de la Santé et des Services sociaux (MSSS) has asked the Agence d’évaluation des technologies et des modes d’intervention en santé (AETMIS) to re-examine the quality of the scientific evidence on which the PQDCS is based and on the pertinence of extend- ing screening to women less than 50 years old. This report evaluates various aspects of the valid- ity of screening trials and their pertinence with regard to the performance and quality assurance of a modern screening program such as the PQDCS.

A screening program targeting women 50 to 69 years old remains justified by the available data. This justification does not extend to younger women. However, it is possible that screening of individual women, based on a personalized risk assessment, might be of benefit to some younger women. This conclusion should be reviewed in several years, when results of the ongoing UK Age Trial become available. In the meantime, a modern mammography screening program like the PQDCS can benefit from measures which aim to maximise the quality of screen- ing and to increase participation rates.