In Depth Look at Breast Screening

In Depth Look at Breast Screening
by Rosalie Bertell, Ph.D., GNSH
October 10, 2002

There is a universal concern among health professionals, about the death rate of breast cancer patients. It is a recognized tragedy in society when a Mother dies. This seriously affects the surviving family, and hence society itself. However, we need to take a serious look at whether or not this concern should be shifted more broadly, so that it embraces the incidence rate of breast cancer, whether or not it is fatal. Any breast cancer disrupts the life of the patient, their family and society. The current disputes with respect to mammography and self-examination revolve around whether or not these practices reduce breast cancer death. I would propose that we consider all of the options relative to breast cancer incidence rate in the hopes that by reducing incidence rate and modifying factors which promote or accelerate breast cancer doubling time (the rate at which the cancer grows), we will also reduce the death rate. I believe that the unusual emphasis on directly reducing death rate has skewed the research, and was bound to be a failure by its own narrow focus.

According to this more preventive approach one can re-visit the major studies underlying the current practices of yearly mammograms and monthly self-examination. These programs are based on the (unproven) philosophy that early detection of a breast cancer will lead to fewer deaths. They are clearly not a preventive strategy for breast cancer, but emphasize early detection.

The Health Insurance Plan (HIP) study in New York, involving 60,000 women followed over 18 years, is considered the “best” study supporting present practice. The women in the study were chosen randomly, and they included (in random way) both women who had never had breast cancer and women who were breast cancer survivors. 30,000 women in the study were given regular mammograms, and 30,000 did not have mammograms.

As this study proceeded, women who developed breast cancer were placed in a treatment program in the hopes that the survival rate of those with early diagnosis, the mammogram patients, would prove to be better than the survival rate of those without mammograms. However, the study soon developed an unexpected problem, namely, some of the breast cancer diagnosis was occuring in women with a history of prior breast cancer. Only women who developed breast cancer in the course of the study were asked about prior breast cancers, so we do not know how many women in each of the two 30,000 groups of women (one with mammography and one without it) had previously had a breast cancer. Questions which we would like to ask, such as how long ago the women had their first diagnosis with breast cancer, and whether the new cancer was in the same breast, were not asked. Because the researchers were intent on the number of cancer deaths of first time breast cancer cases, they merely removed these recurrent cases from the study: about 800 were removed from the mammography group and about 300 from the no-mammography group.

Unanswered Questions: Why were there 2.7 times as many women, (800 with prior breast cancer) diagnosed with breast cancer in the mammography group as compared to the 300 in the no-mammography group? Did the mammography itself increase the rate of breast cancer recurrence? Presumably, if the groups were actually random, there were roughly equal numbers of women with prior breast cancer in each group. If the selection of women was not random, what other differences were there between the mammography group and those not exposed to mammography?

Conclusion of the HIP Study: In the group of women exposed to mammograms, there were 153 breast cancer deaths, and in the no-mammogram group of women there were 196 breast cancer deaths. Based on this death rate: a 22% reduction of death rate was posited for the use of mammography screening.

Re-examination of these results: There is a hidden assumption in this study that either none of the women with recurrent breast cancer died, or that their deaths were unimportant for the purpose of the researchers which was to reduce death in first breast cancer patients. It calls into question the strong recommendation for women at high risk, including those who had prior breast cancer, to have regular mammograms.

Suppose: all of the women who had recurrent breast cancer had died (this information was not reported in the study). This would give 953 deaths in the mammogram group, and 496 in the no mammogram group. Almost twice as many deaths in the mammogram group! You can easily see that various number of deaths in the group of women removed from the study would cause significant differences in the findings of this study. The mammogram group survival rate could be better, the same as, or worse than that of the no mammogram group.

Shift to Incidence Rate: If the incidence rate of breast cancer is studied, this would provide useful information on its benefit or harm, especially for high risk women. This information should have been researched 30 years ago before the strong recommendation for all women over 40 years to submit to regular mammograms.
It is also necessary to determine whether or not mammography examinations are increasing the breast cancer rate, either by initiating new cancers or by detecting small tumours which would never have developed during the lifetime of the women. Radiation exposure is the only proven breast cancer carcinogen, and mammograms deliver the radiation directly to the radiation sensitive breast tissue. There is also evidence that compression of the breast when a cancer is present is able to damage the cellular wall of the cancer and cause metastasis of the cancer to the blood, distributing it throughout the body.

Breast Self-examination: Routinely, those who promote mammography also try to document the inadequacy of reliance only on self-examination. It is actually very difficult to scientifically study self-examination since it depends heavily on the reliability and frequency of what is done by each individual woman in the privacy of her home. Even exposing all women to the same instruction does not guarantee the consistency of technique, and regularity examination. Even if we assume the best possible uniformly good technique, and serious commitment to regularity of examination, the recent Chinese study found the breast cancer death rates in their two groups, with self-examination training and without self-examination training, was statistically the same. Those who were trained in self-examination found more small, probably non-significant tumours (higher incidence rate). This is similar to one of the problems with mammography, namely finding very small tumours which are probably not ever going to be a significant threat to health.

Philosophy: Both the mammography and self-examination experience seems above all to challenge the unproven philosophy that early detection is crucial. I would like to propose another factor which might ultimately prove to be more important than early detection. That factor is the cell replication rate. How rapidly the tumour is doubling in size is a critical factor in how quickly one must act to destroy the malignancy.
According to early research there are basically two breast tumour types, one slow growing and one capable of duplicating its self in about 28 days. I would propose research focusing on the prevention or early detection of the fast growing breast tumours, this is approximately 10% of breast tumours. Obviously you do not want to examine the breast every 28 days with mammography! However, self-examination is ideal for this detection. Instead of diluting the sample with all breast cancers, including those which are probably never going to cause a problem for the woman, a study focused on these aggressive tumours might form the basis for prevention (since recurrence might give clues to the causative agent), early detection and treatment of the most threatening cancers. As a surrogate for self-examination, nurses (such as those at the breast cancer screening clinics in Toronto) could do monthly checks of women in the 50 to 60 year group. Incidence of fast or slow growing breast cancers, determined by biopsy and cell cultivation, should be noted, and recurrence and/or death rates followed for each group. Concentration on non-harmful diagnostic technology, for example thermography, and modern best treatments could be tested for their effectiveness in preventing death for each tumour type. I am sure that some progress (which has so far eluded us) could be made.

Recurrence: There needs to be a special serious study of the recommendation of regular mammograms for women survivors of breast cancer to see whether or not exposure to these X-rays increases the breast cancer recurrence rate. Until proven otherwise, a primary prevention strategy would dictate not recommending mammography.

On one last point, there is also a Swedish study of mammography, often quoted, which gave the promise of a 30% reduction in breast cancer death rate, and which strengthened the commendations of the U.S. National Cancer Institute. This study has also been challenged, primarily because it used as its control group women from a geographical region of Sweden which had a traditionally high rate of breast cancer death. Many flaws in the early studies supportive of mammography have been reviewed and found flawed by two Danish scientist.

For more detail about the raging debate, one can seek the opinion voiced by Dr. Donald Berry, of M.D. Anderson Cancer Center in Houston, Texas or see the summary article by Gina Kolata in the New York Times (Tuesday, 09, April 2002). There is a group, called the PDQ Editorial Board, in the United States, which is responsible for updating the scientific information on the U. S. Government’s main cancer internet site. This group recommended adding to the site by Spring 2002, the warning that mammography’s lifesaving promise is in doubt. According to Dr. Berry, who sits on this Advisory Group, mammography “is something that a woman can reasonably choose not to do and not feel that she’s harming her health.”

The NCI I not bound by the advice of its Advisory Committee, and it continues to strongly recommend mammography to all women over 40 years, even those at high risk of breast cancer.

From the IICPH Resource Centre

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