Cancer incidence estimation at a district level without a national registry: a validation study for 24 cancer sites using French health insurance and registry data.

BACKGROUND: District-level cancer incidence estimation is an important issue in countries without a national cancer registry. This study aims to both evaluate the validity of district-level estimations in France for 24 cancer sites, using health insurance data (ALD demands--Affection de Longue Durée) and to provide estimations when considered valid. Incidence is estimated at a district-level by applying the ratio between the number of first ALD demands and incident cases (ALD/I ratio), observed in those districts with cancer registries, to the number of first ALD demands available in all districts. These district-level estimations are valid if the ratio does not vary greatly across the districts or if variations remain moderate compared with variations in incidence rates. METHODS: Validation was performed in the districts covered by cancer registries over the period 2000-2005. The district variability of the ALD/I ratio was studied, adjusted for age (mixed-effects Poisson model), and compared with the district variability in incidence rate. The epidemiological context is also considered in addition to statistical analyses. RESULTS: District-level estimation using the ALD/I ratio was considered valid for eight cancer sites out of the 24 studied (lip-oral cavity-pharynx, oesophagus, stomach, colon-rectum, lung, breast, ovary and testis) and incidence maps were provided for these cancer sites. CONCLUSION: Estimating cancer incidence at a sub-national level remains a difficult task without a national registry and there are few studies on this topic. Our validation approach may be applied in other countries, using health insurance or hospital discharge data as correlate of incidence.

Are breast cancer screening practices associated with sociodemographic status and healthcare access? Analysis of a French cross-sectional study.

The aim of this study was to analyse the role of women's sociodemographic and healthcare access characteristics according to breast cancer screening practices (organized, individual or no screening). A cross-sectional study was set up in seven French districts using a self-administered postal questionnaire. Randomization was stratified proportionally on age and urban/rural status in each district separately among attendees and nonattendees to the organized breast cancer screening programme (OS). A total of 5638 women aged 50-74 years returned their questionnaires: 1480 in the attendee OS group and 4158 in the nonattendee group. Among them, 3537 declared having undergone a recent mammography outside the organized programme (individual, IS group) and 621 declared never having undergone a mammography or having done so more than 2 years ago (NS group). Analyses showed a gradient between the three groups (IS, OS and NS, respectively) in their association with breast cancer screening practices considering three factors: an increasing gradient was observed for renunciation of basic healthcare for financial reasons, a decreasing gradient in the regular visit to a medical gynaecologist and having had a Pap smear in the last 3 years. Three other variables that showed a decreasing gradient are: living with a partner, current use of hormone replacement therapy and having had a check-up in the last 5 years. In conclusion, the main differences between breast cancer screening practices were largely associated with difficulties in healthcare access, considering regular gynaecological visits in particular.