Brystkræftscreening og overdiagnostik hvordan forstår vi stigningen i incidens?

Transkript

1 Brystkræftscreening og overdiagnostik hvordan forstår vi stigningen i incidens? Henrik Støvring stovring@ph.au.dk 1. December 2016 Institut for Folkesundhed, AU Institutseminar, Vingsted

2 Screening forskningsområdet Seniorforskere Almen Medicin: Annelli Sandbæk, Peter Vedsted Epidemiologi: Henrik Møller, Kim Overvad Sundhedsfremme: Kim Iburg Biostatistik: Michael Væth, Henrik Støvring Med flere... Valgfag på Kandidatdelen 10 ECTS Direkte adgang til at rekruttere studerende fra FSV Metodestærke Kan spottes tidligt på uddannelsen Fx: Mette Lise Lousdal og Mette Møller

3 Institut for Folkesundhedsvidenskab og screening Tværfaglig forskningsgruppe under opbygning Screening bør integreres bedre i den epidemiologiske undervisning Akut brug for de bedste epidemiologiske metoder Samfundsrelevant Fordrer forskellige fagdiscipliner: Statistik Epidemiologi Sundhedstjenesteforskning Sundhedsøkonomi Sundhedskommunikation

4 4

5 Background: A simple screening model Definition af lead time: the length of time diagnosis is advanced by screening (Biesheuvel et. al. Lancet IV Oncol 2007) IV III III II II I I 5

6 Background: More complex scenarios 6

7 Aim Population based, open cohort study: To estimate the effect of introducing a screening program on breast cancer stage distribution by comparing stage specific incidence in women eligible for screening to the corresponding incidence prior to organized screening relative to the concurrent change in younger, ineligible women 7

8 Methods Population All Norwegian women of the relevant age in the relevant period First time DCIS or invasive breast cancer (ICD10 codes: D05 or C50) Period: Birth cohorts: Data Stage, tumor size, and residence at date of diagnosis Birth year Survival after diagnosis Size of source population 8

9 Statistical analysis Relative IRR = IRR eligible IRR ineligible Incidence IRR eligible IRR ineligible Heuer. Biometrics

10 Results 10

11 Results Localized stage (I) Advanced stages (III+IV) Unadjusted analysis (n=43,489) IRR eligible 2.54 (2.44 to 2.65) 0.80 (0.74 to 0.87) IRR ineligible 1.31 (1.23 to 1.40) 0.80 (0.72 to 0.90) Relative IRR 1.94 (1.79 to 2.09) 1.00 (0.87 to 1.15) Adjusted for age and calendar time Relative IRR 1.97 (1.82 to 2.13) 1.04 (0.91 to 1.20) Adjusted for age, calendar time, and interaction Relative IRR 1.69 (1.52 to 1.89) 1.18 (0.95 to 1.45) 11

12 Results Localized stage (I) Advanced stages (III+IV) Continued follow up (n=49,883) Relative IRR 1.68 (1.51 to 1.87) 1.11 (0.90 to 1.36) Compensatory drop more pronounced for stages I and II than advanced stages Excluding prevalence rounds (n=38,807) Relative IRR 1.60 (1.42 to 1.79) 1.08 (0.86 to 1.35) When two youngest cohorts excluded (1.47, 1.30 to 1.66) (1.03, 0.81 to 1.32) 12

13 Manglende fald i avanceret cancer Mulige forklaringer Uobserverbart pga for kort follow up Insensitiv analyse Uobserveret confounding (kohorte/periodeeffekter) Der er ikke noget fald Kan (til dels) undersøges med en lead time simulationsmodel Implementeret i Excel Visualiserer betydningen af analysestrategi prevalence peak compensatory drop Oprindeligt tænkt til brug i undervisning

14 The screening illustrator

15 The screening illustrator The world without screening

16 The screening illustrator Moving cases forward in time (lead time!)

17 The screening illustrator The world with screening moved and non moved cases

18 Computing incidence rates (with screening)

19 Comparing the two worlds Prevalence peak Compensatory drop

20 When would we see a drop in advanced cases? NOTE: Only 20% of advanced cases are moved to another period

21 Conclusion No observed change in incidence of advanced breast cancer is likely because screening cannot prevent advanced cancers We need better understanding of lead times for mammography screening How can we reconcile a finding of reduced mortality with no or minimal prevention of advanced stage breast cancer? Screening poses complex epidemiology questions An important public health topic A core component in any education in public health

22 Thanks for your attention questions welcome! (Aarhus University, March 2016 H Støvring)