In the previous post , we discussed breast precancer. We saw that as mammography picked up earlier and earlier lesions (precancers and early breast cancers), deaths from breast cancer dropped, along with the incidence of invasive breast cancer.
In this graph, which covers the years 1975 to 2007, the top line of bars (blue) represent the incidence of breast cancers (including invasive and non-invasice lesions). The next lower line of bars (maroon) is the incidence of the invasive breast cancers (the kind that account for breast cancer deaths), and the bottom line of bars represents the rate of precancers (ductal carcinoma in situ) collected by SEER.
As you recall from the previous blog , the big drop in cancer death rates did not occur until about 1990, well after there was a rise in the number of diagosed breast precancers.
Why didn't the precancers diagnosed in the 1980s produce an immediate drop in the rate of breast cancer deaths or in the incidence of invasive cancers?
Precancer treatment works like a time machine. When you cure a precancer today, you don't see a reduction in the number of cancers that would arise that same day. You see a reduction in the number of cancers that will arise in some future date (if the precancer had been allowed to develop into a cancer, over time).
If a precancer would ordinarily require 5 years to develop invasive features (i.e., become a cancer), and you diagnose and treat the precancer in 2010, then you will eliminate a cancer that would have occurred in 2015. This explains the delay in the decrease in cancer mortality that you can always expect to see with successful precancer treatment initiatives.
- © 2010 Jules Berman
key words: precancer, precancerous, dcis, ductal carcinoma in situ, breast cancer, breast cancer mortality, cancer prevention, carcinogenesis
About my book, Precancer: The Beginning and the End of Cancer. Nearly every type of cancer passes through a precancer phase, during which it cannot metastasize or invade other tissues. While medicine is not always successful in treating or curing advanced stages of cancers, recent advances in our understanding of carcinogenesis have helped us to develop strategies to prevent, diagnose, and treat many cancers at the precancer stage. Research in this field is escalating rapidly as the evidence increasingly shows that the number of annual cancer deaths could be drastically reduced through the effective treatment and cure of precancer lesions. This book begins by explaining why it has been so difficult to cure cancers, followed by a review of precancer biology, with descriptions of the most common precancer lesions. The final chapters provide practical socio-political and medical goals for precancer treatment, including discussions of the economics and politics of treating precancers.
I urge you to read more about this important topic. Google Books has provided a generous preview of this book.