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Spontaneous remission of breast cancers~ 1 in 5 with no treatment


Article and study~

conclusions from the study for those with short attention spans:

CONCLUSIONS: Because the cumulative incidence among controls never reached that of the screened group, it appears that some breast cancers detected by repeated mammographic screening would not persist to be detectable by a single mammogram at the end of 6 years. This raises the possibility that the natural course of some screen-detected invasive breast cancers is to spontaneously regress.

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http://dartmed.dartmouth.edu/spring09/html/disc_remission.php

DISCOVERIES

Study reveals surprising cancer remission rate

By Jennifer Durgin

When cancer suddenly disappears, people may call it a miracle. But a recent study by three physician-researchers from DMS and Norway found that spontaneous remission of breast cancer is actually quite common. More than one in five invasive cancers detected in the study by mammography vanished without ever being treated.

Findings: Spontaneous remission of breast cancers "has been a taboo concept," says DMS's H. Gilbert Welch, M.D., M.P.H. He helped write up thefindings, which were published in theArchives of Internal Medicine. But the project was initiated by Per-Henrik Zahl, M.D., Ph.D., a senior statistician at the Norwegian Institute of Public Health, and Jan Maehlen, M.D., Ph.D., a pathologist at Ulleval University Hospital in Oslo. Zahl and Maehlen contacted Welch in 2005 after they had difficulty getting their results published, despite a robust study design.

The study compared the number of invasive breast cancers in two nearly identical groups-each with about 100,000 Norwegian women aged 50 to 64. The first group was followed from 1992 to 1997; the second from 1996 to 2001. The key difference between the two periods is that before 1996, Norway had no national breast-cancer screening program, while after 1996, all women aged 50 to 69 were offered a mammogram every two years. So the women in the first group had only one mammogram, at the end of that six-year span. But the women in the second group (the screened group) had three mammograms during that six-year span.

Given the conventional thinking about invasive breast cancer-that it always progresses-one would expect that the total number of cancers detected in each group at the end of six years would be about the same. It wasn't. The incidence of invasive breast cancer was 22% higher in the screened group.

Paper: In the paper, the researchers stop short of questioning the benefits of mammography and instead focus on what the results show about the natural course of invasive breast cancers. Welch insisted on this approach to give the paper a better chance of being published. "We would have never had it

 

Dartmouth's Gil Welch collaborated with two Norwegian researchers on a paper about breast-cancer remission.

published, if not for Welch," says Zahl.

"I didn't want to take on too many things at once," says Welch. "I knew we were going to have a hard enough time with . . . the idea that breast cancers may regress."

Welch's caution seems to have been warranted. In a New York Times article about the study, a representative of the American Cancer Society said, "Their simplification of a complicated issue is both overreaching and alarming."

Spontaneous remission
"has been a taboo 
concept," says Welch.

Editorial: The journal that published the study also seems to have anticipated skepticism. It published a lengthy editorial in support of the study by Robert Kaplan, Ph.D., chair of health services at the University of California at Los Angeles, and Franz Porzsolt, M.D., Ph.D., a German oncologist. "The design of the study has many imperfections," they wrote, "but we should not overlook its strengths. It was population based, it had very high participation, and the outcomes were well documented. . . .

The findings should not be dismissed."

Critics may soon have another study to examine. Zahl recently analyzed breast-cancer data from Sweden, before and after that country instituted a national screening program, and found similar results.

Welch has no plans to collaborate again with the Norwegian team, but he welcomed the opportunity to contribute to the scientific debate about screening. Currently on sabbatical, he is writing a book about the dangers of overdiagnosis-the risks of getting treated for a disease picked up by screening that otherwise wouldn't have caused problems.

As a result of this study, Welch and Zahl believe that a large proportion of breast cancers detected by mammography fall into the overdiagnosis category. The problem is that no one currently knows how to predict which will cause problems and which won't.

"Things are not black and white in screening," says Welch. "Early detection will help some, and it will hurt others. It can do both things at the same time."


 

http://www.ncbi.nlm.nih.gov/pubmed/19029493?ordinalpos=2&itool=EntrezSyst...

Arch Intern Med. 2008 Nov 24;168(21):2311-6.

The natural history of invasive breast cancers detected by screening mammography.

Zahl PHMaehlen JWelch HG.

VA Outcomes Group, Department of Veterans Affairs Medical Center, White River Junction, VT 05009, USA.

Comment in:

 

Abstract

BACKGROUND: The introduction of screening mammography has been associated with sustained increases in breast cancer incidence. The natural history of these screen-detected cancers is not well understood.

METHODS: We compared cumulative breast cancer incidence in age-matched cohorts of women residing in 4 Norwegian counties before and after the initiation of biennial mammography. The screened group included all women who were invited for all 3 rounds of screening during the period 1996 through 2001 (age range in 1996, 50-64 years). The control group included all women who would have been invited for screening had there been a screening program during the period 1992 through 1997 (age range in 1992, 50-64 years). All women in the control group were invited to undergo a 1-time prevalence screen at the end of their observation period. Screening attendance was similar in both groups (screened, 78.3%, and controls, 79.5%). Counts of incident invasive breast cancers were obtained from the Norwegian Cancer Registry (in situ cancers were excluded).

RESULTS: As expected, before the age-matched controls were invited to be screened at the end of their observation period, the cumulative incidence of invasive breast cancer was significantly higher in the screened group than in the controls (4-year cumulative incidence: 1268 vs 810 per 100 000 population; relative rate, 1.57; 95% confidence interval, 1.44-1.70). Even after prevalence screening in controls, however, the cumulative incidence of invasive breast cancer remained 22% higher in the screened group (6-year cumulative incidence: 1909 vs 1564 per 100 000 population; relative rate, 1.22; 95% confidence interval, 1.16-1.30). Higher incidence was observed in screened women at each year of age.

CONCLUSIONS: Because the cumulative incidence among controls never reached that of the screened group, it appears that some breast cancers detected by repeated mammographic screening would not persist to be detectable by a single mammogram at the end of 6 years. This raises the possibility that the natural course of some screen-detected invasive breast cancers is to spontaneously regress.

 

 
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