Abstract
Objective
Residents of rural communities have decreased access to cancer screening and treatments compared to urban residents, though use of resources and patient outcomes have not been assessed with a comprehensive population-based analysis. The objectives of this study were to investigate whether breast cancer screening and treatments were utilized less frequently in rural BC and whether this translated into differences in outcomes.
Methods
All patients diagnosed with breast cancer in British Columbia (BC) during 2002 were identified from the Cancer Registry and linked to the Screening Mammography database. Patient demographics, pathology, stage, treatments, mammography use and death data were abstracted. Patients were categorized as residing in large, small and rural local health authorities (LHAs) using Canadian census information. Use of resources and outcomes were compared across these LHA size categories. We hypothesized that mastectomy rates (instead of breast-conserving surgery) would be higher in rural areas, since breast conservation is standardly accompanied by adjuvant radiotherapy, which has limited availability in rural BC. In contrast we hypothesized that cancer screening and systemic therapy use would be similar, as they are more widely dispersed across BC. Exploratory analyses were performed to assess whether disparities in screening and treatment utilization translated into differences in survival.
Results
2,869 breast cancer patients were included in our study. Patients from rural communities presented with more advanced disease (p=0.01). On multivariable analysis, patients from rural, compared to urban, LHAs were less likely to be screening mammography attendees (OR=0.62; p<0.001). Women from rural communities were less likely to undergo breast-conserving surgery (multivariable OR=0.47; p<0.001). There was no significant difference in use of chemotherapy (p=0.54) or hormonal therapy (p=0.36). The 5-year breast cancer-specific survival for large, small and rural LHAs was 90%, 88% and 86%, respectively (p=0.08), while overall survival was 84%, 81% and 77%, respectively (p=0.01). On multivariable analysis with 7.4 years of median follow-up, neither breast cancer-specific survival (HR=1.16; 0.76–1.76; p=0.49) nor overall survival (HR=1.25; 0.92-1.70; p=0.16) was significantly worse for patients from rural compared to large LHAs.
Conclusion
There was a significant difference in screening mammography use, stage distribution and loco-regional treatments use by population size of LHA. After controlling for differences in patient and tumour factors by LHA, survival was not significantly different.
Keywords: Breast cancer, mammography, breast conserving surgery, mastectomy, rural, hormonal therapy, chemotherapy
Résumé
Objectifs
Comparativement aux résidents des zones urbaines, les résidents des communautés rurales ont moins accès au dépistage et aux traitements du cancer, mais l’on n’a pas encore évalué l’utilisation des ressources par les patients, ni les résultats sanitaires de ces patients, à l’aide d’analyses populationnelles globales. Notre étude visait à déterminer si le dépistage et les traitements du cancer du sein étaient utilisés moins souvent dans les régions rurales de la Colombie-Britannique (C.-B.), et si cela se traduisait par des résultats différents.
Méthode
Nous avons répertorié toutes les personnes ayant reçu un diagnostic de cancer du sein en C.-B. en 2002 en consultant le Registre du cancer, et nous avons lié ces données à celles de la base de données des mammographies de dépistage. Nous en avons extrait les données démographiques, la pathologie, le stade, les traitements, le recours à la mammographie et les données de mortalité des patientes. À l’aide des données du Recensement du Canada, nous avons classé les patientes selon leur lieu de résidence (leur autorité sanitaire locale [ASL]: petite, grande ou rurale), puis comparé l’utilisation des ressources et les résultats sanitaires pour chaque catégorie d’ASL. Nous avons supposé que les taux de mastectomie (par opposition à la chirurgie mammaire conservatrice) seraient supérieurs dans les régions rurales, la conservation du sein étant normalement accompagnée par la radiothérapie adjuvante, laquelle est peu disponible dans les zones rurales de la province. Par contre, nous avons supposé que les taux d’utilisation du dépistage du cancer et des traitements systémiques seraient semblables, car ces services sont disponibles dans toute la province. Nous avons effectué des analyses exploratoires pour déterminer si les disparités dans l’utilisation du dépistage et des traitements se traduisaient par des écarts dans la survie.
Résultats
Notre étude a porté sur 2 869 femmes atteintes de cancer du sein. Les patientes des communautés rurales se sont présentées avec des cancers à un stade plus avancé (p=0,01). Après analyse multivariée, les patientes provenant des ASL rurales, et non urbaines, étaient moins susceptibles d’avoir subi une mammographie de dépistage (RC=0,62; p<0,001). Les femmes des communautés rurales étaient moins susceptibles d’avoir subi une chirurgie mammaire conservatrice (RC multivarié=0,47; p<0,001). Il n’y avait aucun écart significatif dans l’utilisation de la chimiothérapie (p=0,54) ou de l’hormonothérapie (p=0,36). Les taux de survie propres au cancer du sein après cinq ans étaient de 90% dans les grandes ASL, de 88% dans les petites ASL et de 86% dans les ASL rurales (p=0,08), tandis que les taux de survie globaux étaient de 84%, 81% et 77%, respectivement (p=0,01). Après analyse multivariée avec une médiane de 7,4 années de suivi, ni la survie propre au cancer du sein (coefficient de danger [CD]=1,16; 0,76–1,76; p=0,49), ni la survie globale (CD=1,25; 0,92–1,70; p=0,16) n’étaient significativement inférieures chez les patientes des ASL rurales comparativement à celles des grandes ASL.
Conclusion
On observe des écarts significatifs dans le recours aux mammographies de dépistage, la distribution selon le stade de cancer et l’utilisation locale-régionale des traitements en fonction de la taille de la population de l’ASL. Compte tenu des écarts par ASL dans les facteurs liés aux patientes et aux tumeurs, la survie n’était pas significativement différente.
Mots clés: cancer du sein, mammographie, chirurgie mammaire conservatrice, mastectomie, rural, hormonothérapie, chimiothérapie
Footnotes
Acknowledgements: S. Tyldesley and C. Bajdik are recipients of Career Investigator Awards from the Michael Smith Foundation for Health Research. We thank the province’s family physicians for their participation in the care of patients with breast cancer, and for the contributions they make to the patients’ outcomes. We thank Jane Rowlands and Pablo Santibanez for their help with figures. This study was presented at the 2011 American Society of Clinical Oncology (ASCO) Annual Meeting, in Chicago, IL, June 3–7, 2011.
Conflict of Interest: None to declare.
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