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Collections under which this article appears: Cancer: breast Screening

BMJ 2002;325:563 ( 14 September )

News

Annual mammography in women in their 40s does not cut death rate

David Spurgeon, Quebec

Women in their 40s who received annual mammography screening did not have a better survival rate from breast cancer than those who received usual care from their personal physician after an average 13 year follow up, says a report on the Canadian national breast screening study of more than 50000 volunteers (Annals of Internal Medicine 2002;137:305-12)[Medline].

Authors of the study say it is the only trial to date with published results that has focused on women aged 40-49 years.

Dr Cornelia Baines, professor in the public health sciences department at the University of Toronto and a coauthor, said: "The data from this research are quite striking and quite clear. The difference between annual screening compared to the control group is not statistically significant. Breast cancer was not reduced."

The study compared breast cancer mortality in two groups. The first group received screening with annual mammography, physical examination of the breast, and instruction on breast self examination. The second group received the usual care available in the Canadian healthcare system after a single physical breast examination and instruction on breast self examination.

Fifteen Canadian centres took part in the randomised controlled trial, which involved 50430 volunteers recruited from January 1980 to March 1985 who were not pregnant, had no previous breast cancer diagnosis, and had not had mammography in the preceding 12 months.

Physical breast examination and instruction on breast self examination preceded random assignment of 25214 women to receive annual mammography, physical breast examination, and breast self examination and 25216 women to receive usual health care with annual follow up.

The results were measured by looking at the verified breast cancer incidence and cohort mortality up to 31 December 1993 and deaths from breast cancer up to 30 June 1996.

The 105 deaths from breast cancer in the mammography group and the 108 breast cancer deaths in the usual care group yielded a cumulative rate ratio, adjusted for mammography done outside the study, of 1.06 (95% confidence interval 0.80 to 1.40).

A total of 592 cases of invasive breast cancer and 71 cases of in situ breast cancer were diagnosed by 31 December 1993 in the mammography group compared with 552 and 29 cases, respectively, in the usual care group. The expected proportions of non-palpable and small invasive tumours were detected on mammography.

The report concludes that "important questions on mammography screening of women 40-49 years of age still need to be answered... Until the ongoing United Kingdom trial of women recruited at ages 40-41 years reaches fruition, it will be uncertain whether women in their forties benefit from mammography."

The same issue of Annals of Internal Medicine contains the recommendations of the US Preventive Services Task Force, originally released last February, calling for screening mammography, with or without clinical breast examination, every one to two years for women aged 40 and older (BMJ 2002;324:506)[Full Text].

In an editorial (pp 363-4) Dr Steven Goodman, associate professor of oncology, paediatrics, epidemiology, and biostatistics at the Johns Hopkins School of Medicine, says: "Most women are unaware that mammography increases the risk for lumpectomy and mastectomy. Ignoring these extra surgical interventions creates the illusion of almost complete physical safety from mammography, tilting the cost-benefit calculus in a more favorable direction... There will come a time when all the study patients have been followed up, all the analyses have been done, all the expert groups have met, and all the editorials have been written, and we still won't be sure how much benefit and how much harm are caused by mammography."

© BMJ 2002
 

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Collections under which this article appears: Cancer: breast Screening

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