A. Rogel

National cancer incidence is estimated using the incidence/mortality ratio in countries with local incidence data: is this estimation correct?

BACKGROUND In countries with local cancer registration, the national cancer incidence is usually estimated by multiplying the national mortality by the incidence/mortality (I/M) ratio from pooled registries. This study aims at validating this I/M estimation in France, by a comparison with estimation obtained using the ratio of incidence over hospital discharge (I/HD) or the ratio of incidence over health insurance data (long-duration diseases, I/LDD). METHODS This comparison was performed for 22 cancer sites over the period 2004-2006. In France, a longitudinal I/M approach was developed relying on incidence and mortality trend analyses; here, the corresponding estimations of national incidence were extracted for 2004-2006. The I/HD and I/LDD estimations were performed using a common cross-sectional methodology. RESULTS The three estimations were found similar for most cancers. The relative differences in incidence rates (vs. I/M) were below 5% for numerous cancers and below 10% for all cancers but three. The highest differences were observed for thyroid cancer (up to +21% in women and +8% in men), skin melanoma (up to +13% in women and +8% in men), and Hodgkin disease in men (up to +15%). Differences were also observed in women aged over 60 for cervical cancer. Except for thyroid cancer, differences were mainly due to the smoothing performed in the I/M approach. CONCLUSION Our results support the validity of I/M approaches for national estimations, except for thyroid cancer. The longitudinal version of this approach has, furthermore, the advantage of providing smoothed estimations and trend analyses, including useful birth-cohort indicators, and should thus be preferred.

Incidence of major smoking-related cancers: Trends among adults aged 20–44 in France from 1982 to 2012

BACKGROUND Tobacco is currently the largest risk factor for cancers of the lung, lip/oral cavity/pharynx (LOCP) and esophagus. Variations in tobacco consumption over time have led to changes in cancer incidence in the general population. Data on the incidence of cancers at these sites in adults aged 20-44 years old are scarce. Our objective was to provide estimates of incidence trends for these cancers in France among this age group over the last 30 years. METHODS Observed incidence data over the period 1982-2010 for the 20-44 age group were provided from six cancer registries (eight for esophagus) covering approximately 6% of the French population. Age-period-cohort models were used on the observed period, and estimates of cancer incidence for France in 2012 were provided on the basis of short-term predictions. RESULTS In men, a sharp decline was observed over time for LOCP and esophageal cancers, while lung cancer saw only a slight decline. In women, a large increase was seen in lung cancer incidence, while LOCP cancer incidence did not vary significantly. CONCLUSION Smoking behaviors among adults aged 20-44 impact incidence trends in cancers of the lung, LOCP and esophagus, although other factors are involved, particularly in LOCP and esophageal cancers. Our results highlight the importance of preventative efforts which particularly target women aged 20-44. Efforts to curb tobacco smoking in men should also be pursued.

Modelling the effect of breast cancer screening on related mortality using French data

INTRODUCTION This study aimed at modelling the effect of organized breast cancer screening on mortality in France. It combined results from a Markov model for breast cancer progression, to predict number of cases by node status, and from relative survival analyses, to predict deaths. The method estimated the relative risk of mortality at 8 years, in women aged 50-69, between a population screened every two years and a reference population. METHODS Analyses concerned cases diagnosed between 1990 and 1996, with a follow-up up to 2004 for the vital status. Markov models analysed data from 3 screening programs (300,000 mammographies) and took into account opportunistic screening among participants to avoid bias in parameters estimates. We used survival data from cancers in the general population (n=918, 7 cancer registries) and from screened cancers (n=565, 3 cancer registries), after excluding a subgroup of screened cases with a particularly high survival. Sensitivity analyses were performed. RESULTS Markov model main analysis lacked of fit in two out of three districts. Fit was improved in stratified analyses by age or district, though some lack of fit persisted in two districts. Assuming 10% or 20% overdiagnosed screened cancers, mortality reduction was estimated as 23% (95% CI: 4, 38%) and 19% (CI: -3, 35%) respectively. Results were highly sensitive to the exclusion in the screened cancers survival analysis. Conversely, RR estimates varied moderately according to the Markov model parameters used (stratified by age or district). CONCLUSION The study aimed at estimating the effect of screening in a screened population compared to an unscreened control group. Such a control group does not exist in France, and we used a general population contaminated by opportunistic screening to provide a conservative estimate. Conservative choices were systematically adopted to avoid favourable estimates. A selection bias might however affect the estimates, though it should be moderate because extreme social classes are under-represented among participants. This modelling provided broad estimates for the effect of organized biennial screening in France in the early nineteen-nineties. Results will be strengthened with longer follow-up.

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.

Évolution des faux positifs, des cancers in situ et des cancers invasifs de petite taille dans le programme de dépistage organisé du cancer du sein : période 2004–2008

Le programme national de depistage organise du cancer du sein (DO) a ete generalise a l’ensemble du territoire francais en 2004. Ce depistage permet aux femmes une detection precoce de ce cancer afin de reduire sa mortalite. Cependant, le depistage peut aussi induire certains inconvenients, comme produire des resultats faussement positifs, causant du stress. Il peut egalement detecter des cancers peu letaux ou inoffensifs. L’objectif de ce travail est de decrire l’evolution des faux positifs (FP), des cancers invasifs de petite taille et des cancers in situ, en prenant en compte un depistage individuel (DI) avant l’entree dans le DO.