According to www.medscape.com: “November 25, 2008 – A mammography study from Norway has come up with the controversial proposal that one fifth of breast cancer detected on screening may spontaneously regress.”
An interesting study, it purports the idea that not all breast cancers take the same course, suggesting that a percentage will naturally regress. Possible mechanisms that could explain this fascinating hypothesis are not well understood at this time, though a stimulated immune system may be involved. If natural regression is indeed a regular occurrence, it would lead to a dilemma, as practitioners are unable to distinguish between cancers that are likely to regress and those that will continue to develop. Details of the study are included below:
“It found that the cumulative incidence of invasive breast cancer in a cohort of women, aged 50 to 64 years, who received 3 mammograms over 6 years was 22% higher than in a control group of age-matched women who received only 1 mammogram at the end of a 6-year period.”
“We believe that there are ‘pseudo’ cancers in this population [of mammography-screened women], and we suggest that most of these pseudo cancers regress,” he added. What clinicians should do with such pseudo breast cancers is not known, admitted Dr. Maehlen. [ ] However, Dr. Maehlen believes the “first thing we have to accept” is that some detected cancer will not cause symptoms and some will regress. He cites pediatric neuroblastomas as an example of tumors that spontaneously regress.”
“The authors of an accompanying editorial say that the study’s spontaneous regression hypothesis is “difficult to rule out” but impossible to verify without a randomized controlled trial that would leave some participants untreated. The editorialists [ ] credit the study authors with using “a clever study design in an attempt to estimate the value of [mammography] screening.”
[ ] examined breast cancer rates among 119,472 women, aged 50 to 64 years, who were all invited to receive 3 biennial screening mammograms between 1996 and 2001 [ ] a control group of 109,784 women, aged 50 to 64 years in 1992, who would have been invited for screening if the program had existed at that time. Cancers were tracked for 6 years using a national registry. As anticipated, breast cancer rates were higher among screened women than among the control group. “If you screen for cancer, you will find more cancer” [ ]. However, at the end of 6 years, all participants [ ] were invited to undergo a 1-time screening to assess breast cancer prevalence. This is where the researchers found “something much less expected” [ ] “Even after prevalence screening in controls, however, the cumulative incidence of invasive breast cancer remained 22% higher in the screened group,” the authors write.”
“Why the Difference in Rates? [ ] The authors settle on the explanation of spontaneous regression. “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,” the study authors write. They also note that other studies have suggested the same, including a Canadian trial in which the excess incidence of detected breast cancer was also 22% in a screened vs unscreened cohort study model (Ann Intern Med. 2002;137:305-312). Very few case reports support the concept of spontaneous regression. [ ] other countries are just phasing in national programs and could be provide further nonexperimental comparisons, say the editorialists. Arch Intern Med. 2008;168:2311-2316, 2302-2303.”
The concept of spontaneous regression of cancer is not new. While spontaneous regression is generally accepted, the cause and degree of these natural remissions are highly debated. In any case, some will refute the above study, while others will staunchly support it.
If 20% of breast cancers spontaneously regress, it suggests that cancer regression is not as rare as previously believed. It would also support the idea that the body has an innate capacity to, at times, heal itself of serious conditions, and may do so regularly. Why some individuals recover and others do not is not understood. Without a doubt, one conclusion that can be drawn from this study is that cancer regression is an area that warrants further research.