Abstract
Background
The aims of this study were to evaluate the contribution of mobile mammography units to participation rate and to compare their performance to fixed screening centres within the organized mammography screening program of Quebec, Canada.
Methods
The study is based on all screening mammograms carried out in women aged 50–69 who participated in the Québec program from 2002 to 2010. Performance was measured by screening sensitivity, false-positive rate (1-specificity), positive likelihood ratio as well as abnormal call rate, detection rate, interval cancer rate, positive predictive value, and tumour characteristics. Poisson regression models with robust variance estimation were used to take into account the multi-level structure of the data. All models were adjusted for characteristics related to women.
Results
During the 2002–2010 period, 2,292,592 screening mammograms were performed, of which 42,279 (1.8%) were in mobile units. In regions serviced exclusively by mobile units, the participation rate reached an average of 63.4% during the 2006–2010 period compared to 54.7% for the entire study population. Estimated sensitivity was similar to that of fixed sites (rate ratio = 0.98 [0.84–1.15]) while the false-positive rate was lower (rate ratio = 0.76 [0.57–1.02]) although this difference was of marginal statistical significance (p=0.07).
Conclusions
In this program, mobile mammography units allowed regions lacking a fixed centre to attain participation rates slightly higher than those in the rest of Quebec, without loss of sensitivity and with some gain in the false-positive rate.
Key Words: Breast neoplasms, mass screening, mammography, mobile health units, mobile mammography
Résumé
Contexte
Les objectifs de cette étude sont d’évaluer la contribution des unités mobiles en mammographie du Programme québécois de dépistage du cancer du sein sur le taux de participation du programme ainsi que de comparer leur performance à celle des centres fixes.
Méthodes
L’étude est basée sur toutes les mammographies de dépistage réalisées chez des femmes de 50 à 69 ans pour la période 2002 à 2010. La performance des unités mobiles est évaluée à partir de la sensibilité, du taux de faux positif (1-spécificité), du ratio de vraisemblance, du taux de référence pour anomalie, du taux de détection, du taux de cancer d’intervalle, de la valeur prédictive positive et des caractéristiques des cancers. Un modèle de régression de Poisson avec estimation robuste de la variance a été utilisé afin de prendre en compte la structure multiniveaux des données. Les modèles sont ajustés pour les caractéristiques des femmes.
Résultats
Pour la période 2002 à 2010, 2 292 592 mammographies de dépistage ont été réalisées, dont 42 279 (1,8 %) en unités mobiles. Dans les régions desservies uniquement par les unités mobiles, le taux de participation atteint une moyenne de 63,4 % pour la période 2006 à 2010 comparativement à 54,7 % pour l’ensemble de la cohorte à l’étude. La sensibilité était similaire à celle des centres fixes (rapport de risque = 0,98 [0,84–1,15]) tandis que le taux de faux positif était plus faible (rapport de risque = 0,76 [0,57–1,02]), quoique presque statistiquement significatif (p=0,07).
Conclusions
Dans ce programme, les unités mobiles de mammographie permettent aux régions dépourvues de centres fixes d’atteindre un taux de participation légèrement plus élevé que dans le reste du Québec, et ce avec une sensibilité équivalente et un certain gain dans le taux de faux positifs.
Mots Clés: cancer du sein, dépistage systématique, mammographie, unités mobiles
Footnotes
Conflict of Interest: None to declare.
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