Greetings -
Yes, I agree it's strange - not only does that cause lead- and length-time
bias but it's a waste of money to continually reproduce the same errors that
undermine the validity of other trials "proving" the value of mammography
(in my simple brain). Anyway, see Is screening for breast cancer with
mammography justifiable? By Peter C Gøtzsche, Ole Olsen in The Lancet Vol
355 January 8, 2000 for a review of the question and a conclusion that
reads, "...screening for breast cancer with mammography is unjustified" and
calls for further unbiased studies since many prior studies are subject to
the very types of bias you point to.
I am keenly interested in this issue also and will be glad to share
references and ideas (I want to learn from others on this list about this).
Jeanne Lenzer
Freelance writer
191 Otens Rd.
Ellenville, NY 12428
U.S.A.
Phone/pager: (914) 399-5001
Phone/fax: (845) 647-3670 office
Phone: (845) 647-3691 home
[log in to unmask]
-----Original Message-----
From: [log in to unmask]
[mailto:[log in to unmask]]On Behalf Of Klazien
Matter-Walstra
Sent: Saturday, June 02, 2001 5:04 AM
To: [log in to unmask]
Subject: Mammography
Dear List members,
Just lately a new paper in Cancer appeared about breast cancer screening
telling it could reduce breast cancer mortality to 63%( RRR). Compared were
cohorts before any screening was introduced with cohorts during trial
screening and later service screening ( Laszlo Tabar Cancer 2001; volume 91,
number 9 page1724).
In this paper I found one thing strange: women who underwent screening but
of whome the breast cancer was not detected by mammography but clinically
during the screening interval were also put into the screening group.
If you really want to know weather cancers detected by mammography have a
better outcome then clinically detected breast cancers shouldn't these women
not belong to the non screened group ? or at least should you not try to
make both comparisons (when you already have all those data):
1. What does screening do (as done in the paper) ?
2. Does mammography detectection of breast cancer improve survival ?
All comments on this are welcome !
Klazien
_____________________________________________
Klazien Matter-Walstra
Innerbergstrasse 55
CH-3044 Innerberg, Switzerland
tel/fax +41(0)31 829 29 44,
mobile +41(0)79 270 89 69
mailto:[log in to unmask]
http://home.tiscalinet.ch/kmatter
|