Intended for healthcare professionals

Rapid response to:

News Roundup [abridged Versions Appear In The Paper Journal]

Incidence of breast cancer is rising in Australia, while death rate falls

BMJ 2006; 333 doi: https://doi.org/10.1136/bmj.333.7574.876-a (Published 26 October 2006) Cite this as: BMJ 2006;333:876

Rapid Response:

Caution in providing data for "informed" decision

The arguments (limited screening efficacy and overdiagnosis) Dr. Baum
uses to comment the paper of Dr. Pincock are correct in principle, but the
magnitude of the quoted effects is questionable, and this may contribute
to the wrong conclusion.

First, a 20% breast cancer mortality reduction, reported for mammography
screening, relates to randomized studies comparing “invited” versus “not
invited” subjects, and is strongly influenced by compliance in the
screening arm and by opportunistic screening contamination in the control
arm. The chance of mortality reduction for women undergoing screening as
compared to refusers (that is 100% compliance as compared to 0%
contamination) is much higher, probably in the range of 40%, as confirmed
by several case-control studies [1], and this is the risk reduction on
which woman’s decision to undergo screening or not should be based.

Second, a 30% overdiagnosis estimate is among the highest, whereas other
studies, appropriately using a longer follow-up, estimate it in the range
of 5-10% [2-5]. The latter estimates are much more in accordance with the
estimated lead time of about 2 years, whereas a 30% estimate should imply
a much longer lead time (e.g. for prostate cancer screening [6].

Finally, the fact that many have to be screened for one to benefit is a
simple baseline assumption, expected for any secondary prevention measure,
when you are dealing, like for breast cancer, with a disease accounting
for 4% of all deaths in women, or approximately 2% in the screening age.
It is well known that at least 99% of women will be screened
unnecessarily, as screening would not affect their chance of dying, or of
not dying, of breast cancer. But this is true for many other preventive
measures, from cervical and colorectal screening, to most anti-viral
vaccinations, to life-belt use.

It is evident that a 20% mortality reduction and a 30% overdiagnosis rate
is quite a different scenario as compared to 40% mortality reduction and 5
-10% overdiagnosis, as they might support opposite “wise women” decisions.
Everybody agrees that the latter should be “informed”, but the quality of
information should be complete and impartial.

References

[1] Palli D, Del Turco MR, Buiatti E, et al (1986). A case-control
study of the efficacy of a non-randomized breast cancer screening program
in Florence (Italy). Int J Cancer 1986;38:501-504.

[2] Paci E, Duffy S. Overdiagnosis and overtreatment of breast
cancer: overdiagnosis and overtreatment in service screening. Breast
Cancer Res 2005;7:266-270.

[3] Paci E, Warwick J, Falini P, Duffy SW. Overdiagnosis in
screening: is the increase in breast cancer incidence rates a cause for
concern? J Med Screen 2004;11:23-27.

[4] Zackrisson S, Andersson I, Manjer J and Garne JP, Rate of over-
diagnosis of breast cancer 15 years after end of Malmö mammographic
screening trial: follow up study. BMJ 2006;332:689-692.

[5] de Koning HJ, Draisma G, Fracheboud J, de Bruijn A. Overdiagnosis
and overtreatment of breast cancer: microsimulation modelling estimates
based on observed screen and clinical data.
Breast Cancer Res. 2006;8:202.

[6] Draisma G, Boer R, Otto SJ, et al. Lead times and overdetection
due to prostate-specific antigen screening: estimates from the European
Randomized Study of Screening for Prostate Cancer.
J Natl Cancer Inst. 2003 Jun 18;95(12):868-78.

Competing interests:
None declared

Competing interests: No competing interests

30 October 2006
Stefano Ciatto
Head of Dept. Diagnostic Imaging
Centro per lo Studio e la Prevenzione Oncologica, Viale Volta 171, I-50131, Florence, Italy