|
medpundit |
||
 |
 |
|
Tuesday, April 13, 2004In their study of 13 women aged 32 to 59 with these genes, researchers at Columbia-Presbyterian found six had developed breast cancers detected in between their annual mammograms. The average time that had elapsed since their last annual screening was about five months, and four of the six had already developed relatively advanced cancers that had spread to their lymph nodes. "We feel that (every) 12 months definitely is not adequate screening for women with these genetic mutations," said Dr. Ian Komenaka, a breast surgeon and lead author of the study, published on Monday in the online edition of the American Cancer Society journal Cancer. "It looks like it needs to be every six months if not every four months," Komenaka said. The researchers assume that performing mammography more frequently will catch the cancer early enough to prevent it from spreading, thus saving lives. But that is an assumption that cannot be made from their data. Six of the thirteen patients in the study developed breast cancer within 2 to 9 months of having a normal mammogram. Four of them had invasive breast cancer, and three of these had cancer that had already spread to the lymph nodes. The lesson here is that these women had very aggressive cancers - so aggressive that they spread quickly, when the cancer was still very small. It doesn't necessarily follow that finding them earlier will prevent their spread. There's a good chance that they're so aggressive, they begin spreading before they're even detectable. We've been down this road before with chest x-rays and lung cancer: Various proposals to screen smokers for lung cancer were made throughout the 1950s, and by 1959 published reports documented a shift to earlier-stage disease and improved five-year survival rates in patients diagnosed by screening, compared with those diagnosed clinically. Screening smokers by annual chest roentgenograms was subsequently endorsed by the American Cancer Society (ACS), but eventually three large, randomized controlled trials documented no reduction in mortality in the screened population, and the ACS rescinded its recommendation in 1980 The main lesson in this is that lead time bias and length biases are not just theoretical; they confound our ability to evaluate screening programs. We never learn. posted by Sydney on 4/13/2004 07:42:00 AM 0 comments 0 Comments: |
|
