Reports Show Breast Cancer and Age Link : Women 45-49 Have a Better Survival Rate
In what amounts to the discovery of another mystery about breast cancer, Swedish and American researchers have concluded that--for reasons still unidentified--victims who are 45 to 49 when their cancers are diagnosed stand a markedly better chance of surviving than either younger or older women.
And while other scientists who have noted the possible association between age at the time of diagnosis and survival have speculated that greater longevity among such women may be due to body chemistry changes that come with menopause, the Swedish research team says its analysis disproves that connection.
Moreover, the relative survival advantage or disadvantage that is accorded by a woman’s age at diagnosis remains with her for her entire life. A woman who is 30 when her cancer is identified remains at far greater risk of dying from the disease than a woman diagnosed in her 40s, and women who are 45 to 49 when diagnosed apparently never lose their increased survival benefit.
What is clear from data accumulated in a nationwide Swedish cancer registry and a U.S. government-funded data collection program in the San Francisco Bay Area, however, is that women who are in their fifth decade of life when they are diagnosed--especially those 45 to 49--die from breast cancer significantly less often than women in any other age bracket.
Breast cancer is one of the deadliest forms of the disease for women, with 119,900 new cases reported in 1985 and 39,900 deaths nationwide projected for 1986, according to the American Cancer Society. (Breast cancer has recently been surpassed by lung cancer as a killer of women.) Its causes remain unidentified.
Both the Swedish analysis, conducted by a team of doctors at University Hospital in Uppsala, and the American study, at the Stanford University School of Medicine, agree in their analysis of the degree of survival advantage for women by age range. The Swedish team, headed by Dr. Hans-Olov Adami, had earlier published several analyses of data from the same 58,000 Swedish women whose cases were scrutinized in the latest report.
Results of studies by the Swedish and American groups are being published today in the New England Journal of Medicine. Both reports come as new developments in a field in which U.S. researchers are not considered among the world’s best. Papers published in the field in recent years have come from Sweden, Norway, South Africa, Australia and even the Soviet Union, but seldom from American research centers.
A member of the Swedish team, speaking by phone from a cancer conference in Hungary, said the Uppsala researchers have also recently found an unexpected correlation between women who contract breast cancer and the incidence of cancer of the uterine lining--called the endometrium.
For women of middle age and older, Dr. Ingemar Persson said, there appears to be some possible “common factor” that causes both breast and endometrial cancer. Persson said the Swedish team presented its endometrial cancer data for the first time earlier this week at the 14th International Cancer Congress in Budapest.
If the precise chemical mechanism responsible for the unexplained higher survival rates in women in their mid- to late 40s could be identified, doctors might--at least theoretically--be able to use it to alter breast-cancer susceptibility in women in other age brackets. But since the chemical process in question remains unidentified, it is uncertain whether such a development may ever occur.
Adami, who was also attending the Budapest conference, said the Swedish team had not expected to find a specific age bracket--especially the one eventually discovered--with superior survival rates. “I think the most surprising finding was the very rapid decrease (in survival rates) at younger and at early postmenopausal (50 and above) ages,” Adami said in a separate telephone interview. “There is no reasonable biological explanation available.”
Persson noted, moreover, that the significance of age at the time of diagnosis probably has little to do with the effectiveness of breast cancer detection programs but is the result of some idiosyncrasies of body chemistry that change with age but whose actions, for the moment, remain a complete mystery.
Young Women at Risk
Doctors have recognized for several years that young women--those 30 to 35 and under--who get breast cancer have poor prognoses. The Stanford team, agreeing with a variety of previous studies, said poor survival rates in such young Bay Area women may be influenced by the unique hormone changes that occur in the body at the time of pregnancy. Because a higher proportion of women in their 20s and 30s become pregnant than do older women, the pregnancy chemistry influence may skew average breast-cancer rates for all younger women.
It is believed that women who unwittingly become pregnant close to the time breast cancer begins to develop at the initial cellular level may experience unusually rapid growth of their tumors because alterations in their natural hormone mix are conducive to rapid progression of cancer tissue.
While the Swedish survival data was far more detailed than that reported in the Stanford research, both studies generally agreed. Among women diagnosed in Sweden when they were 45 to 49, 89.3% were still living two years after their cancers were identified, 75.8% survived five years and 59.2% were alive 15 years after diagnosis. Women 40 to 44 when diagnosed did nearly as well, with 88.7% alive after two years, 74.4% after five years and 57.9% after 15 years.
For women 30 and under, by contrast, the five-year survival rate was just 62.9% and the 15-year rate was 51.3%.
Survival rates drop off precipitously starting with the age bracket just after 45 to 49 and continue unabated.
Same Drop-Off Pattern
Women 60 to 64 when they were diagnosed survived at a rate of 66% five years after diagnosis and only 42.2% of them were living 15 years later. Five-year survival rates for older women showed the same drop-off pattern, and 15-year rates were very low--but survival that many years for a woman who was 80 at the time of diagnosis, for instance, could be related to a large variety of factors of which cancer is just one, researchers noted.
The Swedish data divided cancer victims into five-year age brackets, from 30 to 79, with separate categories for all women under 30 and those 80 and over.
Adami said there should be no reason to expect survival patterns among American women to be materially different from those of Swedish women, and a graph charting the less specific Stanford data was nearly identical to similar graphs prepared by the Swedish group. The Stanford study examined the cases of nearly 13,000 white women, dividing them into four categories: under 35, 35 to 44, 45 to 49 and 50 to 54 years old.
Because the number of young women in the Swedish data was comparatively small--just 237 of the nearly 58,000 cancer victims there were under 30, for instance--Adami said his team did not attempt to assess the true role of pregnancy-related body chemistry in the eventual result of breast cancer.
But in the cases of middle-aged and older women, Adami said the Swedish data, which relied on tens of thousands of such women, made it possible to test--and, he contended, discredit--speculation that women who are undergoing the natural hormonal changes associated with menopause when their breast cancers develop may contract less deadly forms of the disease than other women. It is a contention the Stanford team, made up of three medical students and a statistician, found valid, however. The Stanford team argued that, because menopause is so directly influenced by hormone changes, the process of menopause itself alters the progression of breast cancer.
Unlike the Stanford team, whose findings were published only as a letter to the editor in the journal, the Swedish researchers included two surgeons, an obstetrician-gynecologist, an epidemiologist and a statistical analyst from the U.S. government’s National Cancer Institute.
Adami said that after close analysis, the Swedish researchers dismissed the occurrence of menopause alone as a breast cancer safeguard because:
- The nature of menopause hormonal changes has no bearing on some forms of breast cancer tumors that develop independent of hormone chemistry.
- A breast cancer detected at about the time of menopause would have to have begun to develop months or years before the chemical changes of menopause began.
- If there was such a link, it would be logical to expect that women who contract breast cancer before menopause would enjoy improved survival after it, but they don’t.
“We conclude that the complex pattern of relative survival as a function of age at diagnosis has to be given serious consideration,” the Swedish team concluded in its research paper, to which the journal gave prominence as a “special article.”
Adami speculated that, though menopause itself may not directly influence breast-cancer survival prospects, it seems likely that some type of hormonal chemistry does play a role. Further research, he said, will have to focus on a range of factors involved in the stimulating role played by hormones in many aspects of total body chemistry.
Identifying the still mysterious age-related factors that influence survival, Adami said in the telephone interview, could be important “as a clue that could suggest how the natural history (of breast cancer) is modified in one way or another by factors relating to age.
“If we knew these factors, we could probably gather very important information for determining the natural progression of this . . . disease.”
Age and Breast Cancer Study SURVIVAL RATE AFTER DIAGNOSIS
Age at At 2 At 5 Diagnosis Years Years (years) (percent) (percent) 30 81.7 62.9 30-34 84.3 64.7 35-39 86.2 70.3 40-44 88.7 74.4 45-49 89.3 75.8 50-54 84.2 68.0 55-59 82.6 64.1 60-64 83.9 66.0 65-69 85.4 69.0 70-74 83.4 67.3 75-79 80.7 63.6 80 76.5 58.4 Total 84.0 68.0
Source: The New England Journal of Medicine
