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Biology 103
2000 Third Web Report
On Serendip

Incidence of breast cancer

Melissa Donimirski

Breast cancer affects hundreds of thousands of women around the United States. Breast cancer is one of the most common cancers that affect women, aside from skin and lung cancer. In fact, one in three women who are diagnosed with cancer will be diagnosed with breast cancer (1). It is expected that in 1997, 180,200 new cases of breast cancer will be diagnosed, and 43,900 women will die (1). Because these numbers are reaching epidemic proportions, the cause of breast cancer is a vastly important topic to consider. It seems very easy to pawn off breast cancer to inherited, problematic genes, known as BRCA1 and BRCA2. These genes, when present, result in a 90% chance of developing breast cancer. However, further research shows that only 5 to 10% of breast cancer cases are due these inherited, mutated genes (2). Thus, 90 to 95% of cancer develops due to other causes. Because the rate of incidence of breast cancer is so high among women, there must be another cause. I would like to suggest that the majority of these cases are due to changeable habits (smoking) and unchangeable environmental (unclean water) causes. I would therefore suggest that the age at which breast cancer is found will decrease as increasing numbers of women begin to pick up unhealthy habits (smoking) and are increasingly exposed to dangerous toxins in various ways (food, water, air) at an earlier age. The age at which these women are exposed to harmful elements then gives the breast cancer more opportunity to form and grow at an earlier chance, thus driving the age of incidence down.

The incidence rates of breast cancer would tend to prove my hypothesis. Breast cancer cases steadily increased by about 1% per year between 1940 and 1982. However, between 1982 and 1987 the increase jumped to 4% per year (3). Possibly, some environmental factors came into play during the 1970‚s, which then affected the breast cancer rates in the 1980‚s. For instance, increased exposure to pesticides or other chemicals could have caused the sudden increase. Or, the use of high-dosage birth control pills, which had just come onto the market may also be to blame.

Some researchers would argue that the increase was due to women putting off childbearing. The age of menarche, age of first child born and age of menopause have all been touted as indicators of risk of breast cancer(1). However I believe this argument is unsubstantiated. Because the increase occurred in the early 1980‚s, women would have had to make childbearing choices many years previous to 1982, approximately 20 years or so earlier. However, during the 1960‚s, although the women‚s movement was in full swing, I argue that women did not yet have the economic independence to make such family planning choices. In addition, I believe the őfree love‚ movement was also a great cause of the baby boomers who are now the legacy of a generation that had many children, as opposed to fewer as the theory would suggest. I do, however, feel that the evidence suggested by the jump in numbers was due to environmental factors. These environmental factors could have affected the age of menarche and menopause, and caused pregnancy to differently affect women‚s bodies, particularly with the advent of new technologies which had never been seen before and are now in use for fertilization, pregnancy, and birth. These technologies include, but are not limited to, drugs used to encourage in vitro fertilization (IVF) as well as other drugs which are now used very commonly to induce birth in women, etc.

Increases with regards to a younger age, however, seem to be unfounded. Increases for women 50 and over saw the most substantial gains in incidence of breast cancer, increasing from 253.9 per 100,000 in 1973 to 364.8 in 1994 among white women, and from 201.1 per 100,000 to304.0 in 1994 for black women (3). However, breast cancer incidence rates increased only slightly for younger women, women under 50, moving from 29.4 per 100,000 in 1973 to 31.1 per 100,000 in 1994 for white women and from 26.0 per 100,000 in 1973 to 34.5 in 1994 (3). Younger women are not being diagnosed with breast cancer at a significantly higher rate. These numbers prove that there is something inherent in the way breast tissue and the way breast cancer functions in old versus younger breasts. The numbers indicating the increase of breast cancer for older women, above the ages of 50, is a significant number. Further, rates for younger women are relatively high at a rate of 660 per year for women aged 15-34 (1). This means that a high enough number of younger women are being diagnosed with breast cancer without having had time to be extremely influence by environmental causes. Further, younger women these days are more exposed to a society in which healthy eating, and exercise are encouraged and obesity and smoking are discouraged and considered unattractive. Because of this, it is more likely for young women to maintain healthier lifestyles than women who grew up during the 1970‚s in the advent of gas-guzzling cars that polluted, unregulated pollution of water and air, and high rates of smoking. Therefore, young women should be having lower, or at least static, rates of breast cancer. Because this is not the case, environmental causes seem to not be the prime cause for breast cancer incidence.

A small portion of the sharp increase of cases could be attributed to mammography and the earlier detection of breast cancer. However, the numbers do not support such a large increase. Should mammography be solely responsible, the number of noninvasive breast cancer diagnoses should be at least comparable to the total increase of breast cancer incidence. However, this does not appear to be so. The incidence of DCIS (noninvasive breast cancer) increased from 2.3 to 6.2 per 100,000 among women under 50, and from 14.3 to 54.6 per 100,000 among women 50 and older(3). Further, women these days, although fully aware of the methods of detection for breast cancer, and the relative risk for diagnosis, do not necessarily follow through. Though more women total are receiving mammography‚s, only one-third of the population of women in the United States receives the amount of care and screening recommended by the major health organizations(1). Although there is certainly a marked and significant increase in detection of breast cancer, it is not enough to account for the extraordinary increase of cancer cases. At most, it accounts for a small portion of the increase. Particularly since many women do not follow-through on their care.

In conclusion, I have found my hypothesis to be incorrect. Younger women (women under the age of 50) have seen only a slight increase in the incidence of breast cancer, while women over the age of 50 have seen a significant increase. Although I do not believe this rules out the possibility of widespread environmental causes for breast cancer, it does shed some small light on the functioning of breast tissue and the development of cancer in young breasts. Perhaps the difference in environmental causes is not the abundance of time, but rather of breast tissue that is older and weakened due to the natural ageing process. This may make older breasts more susceptible to environmental toxins which younger bodies and breasts fight off easily. Or, perhaps, the increased length of time exposed to harmful environmental agents weakens the breasts tissue which then causes it to be more susceptible to mistakes in the cell division process. Obviously, research on the topic is far from finished. As the clock ticks, however, more and more women are diagnosed with breast cancer each year.

WWW Sources

1)Fight breast cancer

2) Breast cancer genes and inheritance

3) Breast Cancer Trend of Black Women Compared With White Women,




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