Screening with mammography uses X-ray imaging to find breast cancer before a lump can be felt. The goal is to treat cancer earlier, when a cure is more likely. The review includes seven trials that involved 600,000 women in the age range 39 to 74 years who were randomly assigned to receive screening mammograms or not. The studies which provided the most reliable information showed that screening did not reduce breast cancer mortality. Studies that were potentially more biased (less carefully done) found that screening reduced breast cancer mortality. However, screening will result in some women getting a cancer diagnosis even though their cancer would not have led to death or sickness. Currently, it is not possible to tell which women these are, and they are therefore likely to have breasts or lumps removed and to receive radiotherapy unnecessarily. If we assume that screening reduces breast cancer mortality by 15% after 13 years of follow-up and that overdiagnosis and overtreatment is at 30%, it means that for every 2000 women invited for screening throughout 10 years, one will avoid dying of breast cancer and 10 healthy women, who would not have been diagnosed if there had not been screening, will be treated unnecessarily. Furthermore, more than 200 women will experience important psychological distress including anxiety and uncertainty for years because of false positive findings.
Women invited to screening should be fully informed of both the benefits and harms. To help ensure that the requirements for informed choice for women contemplating whether or not to attend a screening programme can be met, we have written an evidence-based leaflet for lay people that is available in several languages on www.cochrane.dk. Because of substantial advances in treatment and greater breast cancer awareness since the trials were carried out, it is likely that the absolute effect of screening today is smaller than in the trials. Recent observational studies show more overdiagnosis than in the trials and very little or no reduction in the incidence of advanced cancers with screening.

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Screening for breast cancer with mammography.

To inform the USPSTF recommendations about breast cancer screening, Nelson and coworkers reviewed evidence on the effectiveness of mammography screening in decreasing breast cancer mortality among ...

/pdf/screening-for-breast-cancer-an-update-for-the-u-s-preventive-2lmwsycljt.pdf

Screening for breast cancer: an update for the U.S. Preventive Services Task Force.

https://www.thelancet.com/pdfs/journals/lancet/PIIS0140-6736(02)08020-0.pdf

Long-term effects of mammography screening: updated overview of the Swedish randomised trials

Summary Background Prostate cancer is one of the leading causes of death from malignant disease among men in the developed world. One strategy to decrease the risk of death from this disease is screening with prostate-specific antigen (PSA); however, the extent of benefit and harm with such screening is under continuous debate. Methods In December, 1994, 20 000 men born between 1930 and 1944, randomly sampled from the population register, were randomised by computer in a 1:1 ratio to either a screening group invited for PSA testing every 2 years (n=10 000) or to a control group not invited (n=10 000). Men in the screening group were invited up to the upper age limit (median 69, range 67–71 years) and only men with raised PSA concentrations were offered additional tests such as digital rectal examination and prostate biopsies. The primary endpoint was prostate-cancer specific mortality, analysed according to the intention-to-screen principle. The study is ongoing, with men who have not reached the upper age limit invited for PSA testing. This is the first planned report on cumulative prostate-cancer incidence and mortality calculated up to Dec 31, 2008. This study is registered as an International Standard Randomised Controlled Trial ISRCTN54449243. Findings In each group, 48 men were excluded from the analysis because of death or emigration before the randomisation date, or prevalent prostate cancer. In men randomised to screening, 7578 (76%) of 9952 attended at least once. During a median follow-up of 14 years, 1138 men in the screening group and 718 in the control group were diagnosed with prostate cancer, resulting in a cumulative prostate-cancer incidence of 12·7% in the screening group and 8·2% in the control group (hazard ratio 1·64; 95% CI 1·50–1·80; p Interpretation This study shows that prostate cancer mortality was reduced almost by half over 14 years. However, the risk of over-diagnosis is substantial and the number needed to treat is at least as high as in breast-cancer screening programmes. The benefit of prostate-cancer screening compares favourably to other cancer screening programs. Funding The Swedish Cancer Society, the Swedish Research Council, and the National Cancer Institute.

/pdf/mortality-results-from-the-goteborg-randomised-population-4oiyd8dkop.pdf

Mortality results from the Göteborg randomised population-based prostate-cancer screening trial

In 2003, the American Cancer Society updated its guidelines for early detection of breast cancer based on recommendations from a formal review of evidence and a recent workshop. The new screening recommendations address screening mammography, physical examination, screening older women and women with comorbid conditions, screening women at high risk, and new screening technologies. (CA Cancer J Clin 2003;54:141-169.) © American Cancer Society, 2003.

/pdf/american-cancer-society-guidelines-for-breast-cancer-4wujbcxz3x.pdf

American Cancer Society Guidelines for Breast Cancer Screening: Update 2003

BACKGROUND

Although there is evidence for a reduction in breast carcinoma mortality with mammographic screening, some doubts have been expressed, and there is still uncertainty regarding the age specific effects



METHODS

The authors report on a randomized, controlled trial of mammographic screening for breast carcinoma that was conducted among 51,611 women (21,650 women who were invited to a screening [the study group] and 29,961 women in a control group) ages 39–59 years in Gothenburg, Sweden Among women in the study group, the screening interval was 18 months The screening phase of the trial took place in 1982–1991, and follow-up for breast carcinoma mortality continued until December 31, 1996 Mortality from breast carcinoma was analyzed using a Poisson regression model Overall and age specific effects of invitation to mammography screening on breast carcinoma mortality were calculated Three mortality effects were estimated: the effect on deaths from breast tumors diagnosed during the screening phase of the trial, as assessed by an independent Endpoint Committee (the EPC evaluation model); the effect on deaths from breast carcinoma diagnosed during the screening phase of the trial, as determined by data from the National Cancer Registry and the National Cause of Death Register (the SCB evaluation model); and the effect on deaths from all breast carcinomas diagnosed up to December 31, 1996, as determined by the National Cancer Registry and the National Cause of Death Register (the SCB follow-up model)



RESULTS

A nonsignificant, 21% reduction in the rate of mortality from breast carcinoma with invitation to screening was observed using the EPC evaluation model (relative risk [RR], 079; 95% confidence interval [95% CI], 058–108; P = 014); and a borderline significant, 23% rate reduction was observed using the SCB follow-up model (RR, 077; 95% CI, 060–100; P = 005) Age specific analyses yielded greater mortality rate reductions for the groups of women ages 39–44 years, 45–49 years, and 55–59 years, but there was no mortality rate reduction in the group of women ages 50–54 years The effects of invitation to mammographic screening on the incidence of lymph node-positive disease closely paralleled the effects of invitation on breast carcinoma mortality The effect on breast carcinoma mortality was consistent with the effect on all-cause mortality, suggesting no bias in classification of cause of death Breast carcinoma incidence in the study group was almost identical to the incidence in the control group after trial by screening had ended in the control group (RR, 098; 95% CI, 088–109; P = 07)



CONCLUSIONS

The current results support the commonly observed 20–30% reduction in breast carcinoma mortality with invitation to screening The impression that screening is less effective in women younger than 50 years may be an oversimplification Age specific effects should be a target for further research Cancer 2003;10:2387–96 © 2003 American Cancer Society



DOI 101002/cncr11361

https://acsjournals.onlinelibrary.wiley.com/doi/pdf/10.1002/cncr.11361

Nils Bjurstam

Papers

The Gothenburg Breast Screening Trial.