1 / 19

Does Mammographic Screening reduce the mortality from breast cancer?

Does Mammographic Screening reduce the mortality from breast cancer?. Andy Coldman, Yulia D’yachkova, Norm Phillips, Lisa Kan, Linda Warren. A:. Screening is the use of mammography to identify women likely to have breast cancer who do not have signs or symptoms of the disease.

clovis
Download Presentation

Does Mammographic Screening reduce the mortality from breast cancer?

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Does Mammographic Screening reduce the mortality from breast cancer? Andy Coldman, Yulia D’yachkova, Norm Phillips, Lisa Kan, Linda Warren

  2. A: Screening is the use of mammography to identify women likely to have breast cancer who do not have signs or symptoms of the disease. Q: What is screening Mammography?

  3. A: Randomized control trials (RCT). Women without cancer are randomized to receive (or not) several “rounds” of screening and then followed and their mortality from breast cancer compared. Q: How do we tell if screening works?

  4. Q: So if RCT’s will give us the answer haven’t there been any used to test screening mammography? A: Yes there have, but they don’t all give exactly the same answer.

  5. Results of Randomized Control Trials in Women Age 50 - 74 STUDY MORTALITY CONFIDENCE REDUCTION INTERVAL EDINBURGH 20% - 17% to + 46% MALMO 21% - 24% to + 49% KOPPARBERG 39% 11% to 58% OSTERGOTLAND 31% 6% to 50% NBSS2 3% - 52% to 38% HIP 35% 8% to 54% STOCKHOLM 35% - 8% to 35% GOTHENBURG 9% - 55% to 47% 13% to 31% META ANALYSIS 23% SUMMARY ** Kerlikowshe et al: Jama 273: 149-154

  6. Results of Randomized Trials for Women Age 40 - 49 STUDY MORTALITY CONFIDENCE INTERVAL REDUCTION EDINBURGH 19% - 67% to 46% MALMO 36% - 11 % to 55% - 2% - 77% to 41% OSTERGOTLAND KOPPARBERG 33% 5% to 63% NBSS1 - 14% - 56% to 17% HIP 23% - 11% to 47% STOCKHOLM - 1% - 101% to 49% GOTHENBURG 44% 2% to 68% 5% to 29% META ANALYSIS 18% SUMMARY ** Herdrick et al: JNCI 22:87-92

  7. Q: Haven’t the results of these trials been challenged and disproven? A: • A small number of authors have been critical of these studies and this has received a lot of media attention. The major criticisms have been: • 1. The multiple reports from individual trials • provide inconsistent numbers. • 2. That randomization was flawed in several • of the trials. • 3. That the trials used deaths from breast • cancer, rather than deaths from all causes • in measuring outcome.

  8. 1. The multiple reports from individual trials provide inconsistent numbers. • It is true that numbers from each report from a trial does not have exactly the same numbers. This has been generally been caused by blinded review processes which have changed the eligibility of some cases. In all trials the magnitude of such changes is small so that results are unaffected.

  9. 2. That randomization was flawed in several of the trials • Not all trials used individual randomization but randomized districts and then included all eligible women in those districts into the trial. Consequently the two arms (screening v non-screening) were not exactly balanced. Whilst true the differences were extremely small and were more often in the direction not favouring screening.

  10. 3. That the trials used deaths from breast cancer, rather than deaths from all causes in measuring outcome. • Although breast cancer is an important cause of death most women in screening studies die of other causes. Thus the effect of screening on breast cancer gets lost when all causes are used. Nevertheless a recent analysis of some trials show that all-cause mortality is reduced.

  11. These criticisms have been reviewed by a number of expert committees and have been concluded to be unfounded. • Every western country recommends mammography screening in women only the age ranges differ.

  12. Q: What is the situation in BC regarding mammographic screening? A: • Screening began in 1988. • Screening is offered across the province in 40 affiliated centres. • Screening offered to women aged 40-79 and targeted to women 50-74. • 50% of women 50-74 are screened every 2 years. • 230,000 screens will be performed in 2003.

  13. All Ages with 95% CI Breast (Female) Age 0-44 With  10 cases per year Age 45-64 Age 65+ Females 200 200 200 Incidence Mortality 150 150 150 125 125 125 Relative rate (% log scale) 100 100 100 80 80 80 70 70 70 60 60 60 50 50 50 1974 1980 1986 1992 1998 1974 1980 1986 1992 1998 Year of diagnosis Year of death Trends in Breast Cancer Incidence and Mortality by Age Between 1974 - 98

  14. Numbers of Cancers Detected at Screening by year 1993 - 2002

  15. Stage Distribution of Cancers in Screened and Un-screened British Columbia Women in 1995

  16. Observed Percentage Point Increase in 5 - Year Relative Survival by Stage for Cases Referred to BCCA 1987 - 96 and All Cases in Province

  17. 5 Year Relative Survival Unscreened versus Screen Detected Cancers Referred to BCCA 1990 - 1996

  18. 0.0035 Observed Expected 0.0030 0.0025 0.0020 0.0015 0.0010 0.0005 0.0000 0 2 4 6 8 10 Observed and Expected Breast Cancer mortality rates by time since first screen for women screened at least once between ages 50-74

  19. Conclusions • Yes mammographic screening has been demonstrated to reduce mortality in RCT’s. • Screening is detecting increasing numbers of cancers in BC. • Screen detected cancers have a better prognosis. • Breast cancer mortality is lower in BC women who use screening.

More Related