War on Cancer by Ralph W. Moss, PhD (www.cancerdeclslons.com)
Townsend Letters April 2009
CBS Gives Me Unwanted Attention
Study Suggests that Some Breast Cancers May Disappear
Cancers, even :advanced cancers, can sometimes undergo what is called "spontaneous regression" - that is, they can simply shrink or disappear without trace. This is a phenomenon .well known to medical science since at least the 19th century. In the 1960s, Dr. Tilden C. Everson and Warren H. Cole wrote a celebrated little book on the topic, Spontaneous Regression of Cancer.' Spontaneous regressions remain poorly understood and have generally been thought to occur very rarely. But a recent study carried out by team of researchers, led by epidemiologist H. Gilbert Welch, MD, of Dartmouth Medical School, suggests that spontaneous regression of breast cancer may be considerably more common than previously thought.
The Welch study, published in the journal Archives of Internal Medicine, followed a group of almost 110,000 Norwegian women who underwent periodic mammography screening for breast cancer over a five-year period between 1992 and 1997, and compared them with a second, matched group of women who did not undergo regular routine breast cancer screening during the same period. Surprisingly, the women who underwent regular screening had 22% more invasive breast cancers than those who did not."2
Welch and his colleagues suggest that the most plausible explanation for this discrepancy is that many of the women in the unscreened group had an equivalent number of cancers; but, in the absence of screening, those cancers went undetected and therefore untreated. Furthermore, rather than progressing, those cancers may have simply resolved and disappeared over time.
Up to one-fifth of all breast cancers that are detected by mammographic screening may potentially resolve themselves without treatment. "Because the cumulative incidence among controls never reached that of the screened group," the authors wrote, "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's conclusions were considered important enough to be featured in the New York Times. In an interview with medical reporter Gina Kolata, Dr. Welch explained the study's controversial conclusion, that "there are some women who had cancer at one point, and who later don't have that cancer."3
I have previously discussed the risks and benefits of screening mammography. Indeed, I have published an investigative report on "Mammography, Biopsy and the Diagnosis of Breast Cancer" (available from my Web site, wwwcancerdecisions.com).
Several of my readers have suggested that the higher breast cancer rate noted in the Welch study among women who underwent regular screening mammography (as compared with those who were only screened once, at the end of the study's six-year span) might have been due to radiation exposure from the mammography procedure itself.
Although there is some evidence that exposure to ionizing radiation from screening can contribute to an increased risk of breast cancer, it would take from 10 to 25 years for such a risk to be realized in terms of increased breast cancer incidence. In other words, the 22% difference in breast cancer incidence between the women who received regular mammographic screening over the six-year span of this study cannot be attributed to radiation exposure from the imaging procedure alone.
There is other evidence to suggest that a significant proportion of the abnormalities detected on mammography may in fact not represent an immediate threat. They may instead represent "overdiagnosis" - that is, the detection of lesions that, left alone, might never progress to invasive cancer at all. But Welch's study takes this possibility one step further. "We believe that there are 'pseudo' cancers in this population of mammographically screened women] and we suggest that most of these pseudo cancers regress," said Jan Maehlen, MD, professor of pathology at the Ulleval University Hospital in Oslo, Norway, and one 'of the study authors, in an interview with the online medical forum Medscape.4
The study was considered sufficiently important to merit an accompanying editorial in Archives of Internal Medicine (an American Medical Association publication). The authors of the editorial point out that it will be impossible to verify whether the 22% difference in breast-cancer diagnoses between screened and unscreened women is indeed due to spontaneous regression of breast cancers unless a full-scale clinical trial is performed. That said, it would probably never be possible to conduct such a trial, since it would probably be considered unethical to leave one group of women untreated. "Despite the appeal of early detection of breast cancer," wrote the editorialists, "uncertainty about the value of mammography continues."
This study is not the first to raise troubling questions about the natural history of certain breast cancers and the risks versus the benefits of screening mammography. For example, an earlier study carried out in Canada in 2002 also found an identical 22% difference in cancer diagnoses between women who went unscreened and those given regular mammograms.5 Another study published in the influential British Medical Journal in 2004, reported similar rates of overdiagnosis, concluding "Without screening, one third of all invasive breast cancers in the age group 50-69 years would not have been detected in the patients' lifetime. This level of over-diagnosis is larger than previously thought."6
This makes the picture rather complicated. There is no doubt that, when detected in its early stages, breast cancer is very often curable in the truest sense of that word; and screening mammography may be useful as a component of an early detection program. But, as with any medical procedure, there are risks as well as benefits to screening for cancer; and the possibility of overdiagnosis leading to unnecessary treatment is an inherent drawback.
The Welch study (as with his other provocative writings) is already causing considerable controversy. Robert A. Smith, director of breast cancer screening at the American Cancer Society (ACS), has commented in an intemperate way on the study: "Their [the authors'] simplification of a complicated issue is both overreaching and alarming," he told the New York Times. The ACS has long been a staunch promoter of screening mammography.
Yet the design of the latest study was indisputably an ingenious one, and the findings demand further investigation. The purpose of the study was to quantify the potential size of the overdiagnosis/overtreatment problem - a problem that even proponents of screening mammography acknowledge exists. In their conclusions, the authors take pains to point out that their aim was not to credit the use of mammography in screening for breast cancer.
It is also important," they write, "to emphasize that our findings have no bearing on the-debate on whether screening mammography reduces breast cancer mortality. Our findings are equally consistent with the possibility that mammography either leads to a reduction in breast cancer mortality or has no effect at all. Instead, our findings simply provide new insight into what is arguably the major harm associated with mammographic screening, namely, the detection and treatment of cancers that would otherwise regress."
Another important consideration (and one that the archives of Internal Medicine study was not designed to address) is the contribution of radiation exposure from repeated mammograms to the overall incidence of breast cancer. Despite emphatic assurances concerning the safety of mammography, it is acknowledged by experts that the procedure (like all exposure to ionizing rays) does somewhat heighten the risk of radiation-induced cancer. This is particularly so when a mammogram has to be repeated because of questionable readings. The danger begins to add up when hundreds of thousands of women are being screened annually. The. risk of radiation-induced cancer needs to be taken into account in making the decision as to when to begin regular screening mammography.
There is no doubt that every life saved ,is something to celebrate. But there is legitimate cause for concern that a significant number of women are being treated unnecessarily for abnormalities that might never have become clinically apparent or represented any threat to life. The onus is now on the cancer-research community and the medical profession to look long and hard at the basic assumptions underlying the wide-scale adoption of mammographic screening programs. After all, if one could identify in advance which tumors are likely to progress to cancer, and which are just a temporary aberration, a great many women could be spared the ravages of aggressive treatment.
2. Zahl P-H, Maehlen L Welch detected by screening 2316.
3. Kolata G. Study suggests some cancers may go away. 2008.
4. Mulcahy N. Mammography study suggests some spontaneously regress. Medscape Medical News. NQ,VP,nDI2r www.medscape.com/viewarticle/584147 [subscription
5. Miller AB, To T, Baines C], et al. The Canadian Study-1: breast cancer mortal ity after 11 to 16 screening trial of mammography in women age 40 2002;l37(5 pt 1):305-312.
6. Zahl P-H, Strand BH, Maehlen J. Incidence of
Sweden during introduction of nationwide <n·ppnin,,,· prospe(;trV~) 8M). 2004;328(7445):921-924.