3 / 2000
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MAMMOGRAPHY SCREENING IS WOMAN´S HEALTH INSURANCE
Mammographic classification seems to reliably predict good and poor long-term outcomes for survival of breast cancer tumours of 14 mm or smaller, and especially for those smaller than 10 mm. The implications for therapy are substantial. Peter B. Dean, MD, Professor of Diagnostic Radiology in the University of Turku, is a member of the research group, which published the results of a long-term research project in the Lancet in February this year.
Altogether 343 tumours were investigated in the study, which started in 1977 and continued for over twenty years. Dr László Tabár, working at the Department of Mammography at the Falun Central Hospital, Sweden, was the principal investigator of the research. All the women involved are from Falun (Dalarna) county and the work was mainly done there.
The women in Falun were invited to mammography screening and the research was done as a population trial. Two thirds of the women were initially invited to mammography and after five years the remaining third was also invited.
"There was quite a difference in breast cancer incidence among those who were first invited and those who were invited later. We can definitely say that mammography screening does decrease the mortality from breast cancer. The study was done jointly with the county of Linköping so that the two Swedish counties were combined in the final report", explains Professor Dean, who has just been elected President of the Radiological Society in Finland.
Professor Peter B. Dean started work in the field in 1974, when Professor Pekka Virtama asked him to start working with mammography.
"I have been working at Turku University Central Hospital since 1972. I first studied chemical engineering at Cornell University in New York State and then went to medical school at Harvard University, where I graduated in 1971. The following year I came to Turku. In between I have spent two years in the States and about one year in Sweden."
"Mammography screening is done in societies that care about women’s health. Of course it is also a question of money: the society should have or should be willing to spend the money needed. Mammography screening is restricted to western societies where breast cancer is a real health problem. Breast cancer is a disease of a rich society. The greater frequency of the disease in wealthier countries may have something to do with nutrition, but there is so much about the origin of the disease that we don’t yet really understand", says Professor Peter B. Dean. Tabár was the best teacher
Mammography was not at all easy in the beginning. The film quality was not very good and Dean felt that he lacked knowledge. Professor Virtama arranged for a teaching programme on mammography for the young researchers.
"But the most useful teaching was given by a young physician working in Helsinki, László Tabár. It was immediately obvious that he knew more about mammography than anyone else around did and he also knew how to teach it. He came to Turku in 1976 and spent a month here. He basically revolutionised our mammography service here."
"The following year he was invited to Falun to start a mammography screening programme there. Since then he and I have been working together on many projects. We have published quite a few papers and also a book called Teaching Atlas of Mammography, the first edition published in 1983."
The third edition will come out this year. This book has been rather popular in teaching the basics of mammography.
"In the book we describe the classification of mammograms. Tabár refined the system that is described in the Lancet article. He refined a classification of mammograms in 1977 that made this very long-term prospective study possible."
In Sweden the first screening programme began in 1972 in Gävle, then in Malmö, Falun, Linköping, Stockholm...and the final screening was started in 1997 in Visby, Gotland.
"When the results of Falun and Linköping were published in the Lancet in 1985, it aroused the attention of the Finnish authorities who decided to start screening in Finland. In Finland the screening began in 1987 based largely on the recommendations of László Tabár, who also came here to train Finnish radiologists how to read mammograms and how to perform treatment. All the Finnish radiologists attended his courses. He is now an honorary member of the Radiological Society in Finland."
In Sweden more women screened
In Finland there are more than 3,000 breast cancer cases a year. The death rate from breast cancer is now fairly low: about 80 percent of the women who have had breast cancer are alive after five years. Sweden has a slightly higher incidence of breast cancer than Finland but a lower death rate, most likely because of the screening.
"Screening also makes women more aware of the fact that they should check their breasts themselves and go to the doctor whenever they find something unusual."
"In Finland, the screening of women in the age group 50 to 59 was started with the promise that the screening would expand to older age groups. However, this promise was not kept. We are still basically at the preliminary phase after 13 years. In fact in many municipalities they have cut back screening, but still almost everywhere in Finland women aged 50 and 59 are screened. Helsinki "saves" a few marks by screening only until age 57."
In Sweden, the situation is much better: the recommendation is that all women between 40 and 69 should be screened.
Professor Dean says that so far mammography is the best way to find breast cancer, but it is not a perfect system. With mammography a tumour as small as three millimetres can often be found.
"We try to find the tumours that are smaller than one centimetre, although the smaller the tumour, the more it looks like normal breast tissue and the harder it is to find on the mammogram."
More survival and less treatment
The most usual way to treat breast cancer is to operate the tumour.
"The smaller the cancer, the smaller the operation", Peter B. Dean says.
"In the latest Lancet article we were able to demonstrate that following operation for small breast cancers (under 15 mm), a majority of the women were still alive twenty years after treatment. A minority died of something else, and only a very few actually died of breast cancer. And almost all of those who died of breast cancer had one particular, uncommon but deadly type of breast cancer that was distinguished on the mammograms 20 years ago."
"Once those have been separated out, the rest of the women with tumours under 15 mm had nearly perfect survival. They have remained free of breast cancer after an operation and in some cases radiation therapy, which was given to about one third of the women. That was enough."
"In the United States it has nowadays become more popular to give chemotherapy to smaller and smaller cancers, although there is no evidence that it helps in these smaller cancers. Our study shows that small cancers do not need it, because survival is nearly 100 percent."
"This is good news for women who might have breast cancer. With the help of screening you are much more likely to survive and to survive with less treatment."
Did the results reported in the latest Lancet article include any new aspects?
"Not really", says Professor Dean. "But now we can prove to other people what we knew a long time ago. Women with very small breast cancers seldom, if ever, die from breast cancer. Regular mammography screening reduces the death rate of breast cancer."
Professor Dean recommends that women should go to mammography screening every year or every second year.
"The average age of menopause in Finland is 53. The pre-menopausal women should be screened every year or every one and a half years at the most. In these younger women, breast cancer grows faster and becomes more malignant at a faster rate. Breast cancer often starts out as a low-grade malignancy, but when it grows, some cells may transform to a higher malignancy grade. This happens more frequently in younger women."
There is also the question of radiation from mammography. "The latest consensus from the United States is that yearly mammograms starting at the age of 35 are more beneficial than harmful. I believe that one can recommend screening from the age of 35 even when our epidemiological data apply to women aged 40 and older."
Another research project is under way
"We are reviewing all the breast cancer cases from the past 40 years in Dalarna County, Sweden, to see how the introduction of mammography screening has influenced survival and, more importantly, mortality. Working in the mammography working group of the Radiological Society of Finland, we have also collected all the screening data from women aged 50 and older who have been screened in Finland since 1987."
"The actual number of screened women peaked in 1991 and dropped again within the next two years "thanks to" the recession in Finland in the early 1990´s and saving money by cutting down the mammography screening here and there. When screening increased later in the 1990s, the women who had been temporarily "dropped" from screening were again sent invitations. It appears that when they finally came back to screening, a lot more of the larger cancers were detected; cancers that had grown to a larger size during the interruption of screening."
"Should we hold the politicians responsible?" asks Professor Dean.
László Tabár, Hsiu-Hsi Chen, Stephen W. Duffy, M.F. Yen, C.F. Chiang, Peter B. Dean, Robert A. Smith:
A novel method for prediction of long-term outcome of women with T1a, T1b, and 10–14 mm invasive breast cancers: a prospective study. Lancet, volume 355, number 9202, 5 February 2000.
Paula Heino
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