Letters

Rapid Responses from bmj.com

Confounding factor

Misleading paper

Study internally invalid

From BMJ USA 2002;October:560

Following are edited excerpts from Rapid Responses generated by this article, which can be read in their entirety at http://bmj.com/cgi/eletters/325/7361/418Editor

Confounding factor

EDITORWe are not shown the trend in mastectomies prior to 1990 and whether a downward trend had preceded screening mammography. It should be noted that from the mid-1980s it was recognized that lumpectomy was as effective as mastectomy. This change in surgical practice might explain the observed reduction in mastectomy rates rather than breast screening.

Des Spence, general practitioner. 
Glasgow, UK destwo{at}yahoo.co.uk

Misleading paper

EDITORSince the mastectomy rate has gone down steadily for many years, also in countries without screening, it is only to be expected that Paci and colleagues would find a decrease in the mastectomy rate in the period 1990-1996 in Florence, when screening was introduced. The relevant question is whether the decline in the mastectomy rate is slower when women are invited to participate in screening programs than when they are not invited.

In our recent Lancet article, we reported evidence from the randomized trials of screening that this is the case. Furthermore, the authors' findings from Florence are contradicted by a far larger study from the southeast Netherlands, where screening was introduced in the same time period. I calculated that the number of invasive cases increased by 78%, the number of women who underwent breast-conserving surgery increased by 71%, and the number of women who underwent mastectomy increased by 84% (Eur J Cancer 2002;38:1288). What is more, these authors did not include carcinoma in situ, which is rarely detected without screening but is frequently treated by mastectomy. At present, breast cancer screening is not possible without overdiagnosis and overtreatment. This also applies to mastectomies. It should also be remembered that breast-conserving surgery with radiotherapy is a pretty rough treatment, which can lead to decreased survival (Lancet 2000;355:1757-1770).

Peter C Gøtzsche, director. 
Nordic Cochrane Centre, Rigshospitalet, Denmark pcg{at}cochrane.dk

Study internally invalid

EDITORNo mention is made as to whether the lumpectomies as described were purely therapeutic or included diagnostic breast biopsies resulting from screening. Thus, the meaning of the terms "breast conserving surgery" and "lumpectomy" requires clarification. Hidden within the observed increase in "breast-conserving surgery" could well be unnecessary biopsies for falsely positive mammograms. It would be dangerous to assume that all "lumpectomies" were performed for therapeutic intent only. The figure presented in the article would have been more meaningful if it reported the observed rates of better defined surgical categories in the screened versus the non-screened population. As presented the reported mastectomy rate is purely a quantitative observation, from which no qualitative inference as to the underlying reasons can be made.

Richard H Moore, fellow in breast surgery. 
University of Hull, Cottingham, UK ric.moore{at}virgin.net