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This report, Breast Cancer in New Jersey 1979-1995, examines breast cancer incidence and mortality in New Jersey from 1979 through 1995 and presents data on stage at diagnosis, which is an important factor in survival of breast cancer. It also compares New Jersey with the United States for the combined years 1989 through 1993. Information on mammography screening in New Jersey also is included. (Please see the Glossary for definitions of incidence and mortality as well as other terms.)
Information on Breast Cancer
Breast cancer is the most common cancer among women, except for skin cancer. The American Cancer Society estimates that one in eight women in the U.S. will be diagnosed with breast cancer in her lifetime. The causes of breast cancer are not all known; however, some risk factors are well recognized. The risk of breast cancer increases greatly with age. The risk factors also include a variety of reproductive and hormonal factors such as having no children, having the first birth at a late age, early onset of menstruation, and late menopause. Women with a personal or family history of breast cancer are at higher risk, as are women with mutations in either of two genes - BRCA-1 and BRCA-2. High educational and socio-economic levels are linked with greater risk, probably due to their association with the reproductive risk factors. Jewish women also are known to be at higher risk of breast cancer, while black women have lower rates of the disease than white women. Certain types of benign breast disease (fibrocystic, fibroadenoma), obesity after menopause, and moderate to heavy alcohol consumption (3 or more drinks per day) also are associated with breast cancer. Very high doses of radiation, such as used in radiation therapy, have been shown to cause breast cancer. Long-term use of estrogen replacement therapy after menopause may increase the risk of breast cancer. Some recent studies suggest a possible increase in breast cancer before age 45 among women who used oral contraceptives for a long time or who started oral contraceptive use at an early age. Other factors that may be associated with breast cancer are lack of physical activity and a diet high in fat. To date, environmental exposures have not been found to cause breast cancer, but pesticide and other chemical exposures which mimic or modify the action of estrogens and gene-environmental interactions are under study now.
Breast Cancer Incidence Among New Jersey Women
During the years 1979 through 1995, the annual incidence of breast cancer among women in New Jersey varied from over 4,000 to over 6,000 cases with a peak of 6,089 cases in 1992. The annual age-adjusted incidence rate (new cases per 100,000 women) peaked in 1988 at 119.2 and then declined to 105.5 in 1995. Each year white women had a higher age-adjusted incidence rate than black women. However, while the incidence rate among white women steadily declined between 1991 and 1995, the incidence rate among black women declined in 1993 and 1994 and then increased again in 1995. Between 1985 and 1995, the annual proportion of breast cancer cases diagnosed in the early stages of the disease (in- situ, localized) increased from 49 percent to 64 percent. However, black women had a lower percentage of their breast cancers diagnosed at these early stages than did white women.
More widespread use of screening methods such as mammography, which identify breast cancer early, may explain at least part of the increase in the breast cancer incidence rates among New Jersey women between 1979 and 1988. The drop in the incidence rates after 1988 could be because some women who would have been diagnosed after 1988 with later stage disease already had been diagnosed as a result of screening. This pattern of increases and then decreases in incidence rates is typical after widespread use of a new screening method.
Breast Cancer Mortality Among New Jersey Women
About 1,500 to 1,800 deaths due to breast cancer occurred each year among New Jersey women in 1979 through 1995. The annual age- adjusted mortality rate (deaths per 100,000 women) fluctuated between 27.1 and 33.2; but in the three most recent years the rate was lower than in the previous 14 years. During the years 1979 through 1989, black women sometimes had a higher mortality rate and sometimes a lower mortality rate than white women. In the most recent years, 1990 through 1995, black women consistently had a higher mortality rate than white women. The decline in breast cancer deaths among New Jersey women may be due to more women using screening methods that identify breast cancer early. The survival rate for women with breast cancer diagnosed in the early stages is much greater than the survival rate for women with breast cancer diagnosed in the later stages of the disease.
Recent Incidence and Mortality Trends - Differences Between White and Black Women
While the overall picture of breast cancer among New Jersey women is encouraging, there is need for improvement, particularly for some groups of women. The recent decrease in breast cancer incidence rates and mortality rates appears not to have occurred as consistently among black women as among white women. And, although black women's annual incidence rates were lower than those of white women, black women's mortality rates were higher than white women's mortality rates in the most recent years. The reasons for the black women's lower incidence of breast cancer may be partially due to differences in risk factors. The higher mortality rates among black women may be explained by the higher percentage of breast cancers diagnosed in the later stages and differences in the cancerous tumors, socio-economic factors, and treatment.
Mammography Screening Among New Jersey Women
According to data collected in the Behavioral Risk Factor Surveillance System, in 1991, 69 percent of women age 40 and over had ever had a mammogram; in 1995 the percentage increased to 78 percent. However, a substantial percentage of women in this age group had never had a mammogram - 22 percent in 1995. The percentage of women age 40 and over who had a mammogram in the previous two years also increased, though not as much.
Breast Cancer in New Jersey Compared with the U.S.
For the combined years 1989 through 1993, the age-adjusted incidence and mortality rates for breast cancer among New Jersey women were higher than in the U.S. Why the breast cancer incidence and mortality rates among New Jersey women are higher than the U.S. rates is not completely understood, but the answer probably lies in a combination of known risk factors for breast cancer and in other risk factors which are as yet unknown. Several recent studies have found that known breast cancer risk factors explain much of the differences in breast cancer incidence rates and mortality rates among the different regions of the country. One very recent study, which compared breast cancer incidence and mortality among women in the Northeast, California, the Midwest, and the South, did not find an excess in breast cancer rates in the Northeast after adjusting for age and many known breast cancer risk factors. An earlier study found that fifty percent of the excess in breast cancer mortality rates among white women in the Northeast compared to the South (the region of the country with the lowest breast cancer mortality rates) was explained by several recognized breast cancer risk factors. Another study found that elevated breast cancer incidence rates in the San Francisco Bay Area, which has the highest rates in the country, were completely accounted for by regional differences in the known risk factors for breast cancer.
Breast Cancer Incidence and Mortality Rates for 1996
Preliminary breast cancer incidence data for 1996 show that the declining trend continued for all, white, and black women. Breast cancer mortality data for 1996 also show a continued decline for all and white women, but the mortality rate for black women increased.
Breast cancer incidence has recently declined in New Jersey and the U.S. However, the rates in New Jersey remain higher than in the U.S. While white women are more likely to get breast cancer than black women, black women are more likely to be diagnosed at a later stage and are more likely to die of the disease. Additional research is needed on the causes and the means to prevent breast cancer. At this time, early detection and treatment are the best methods to reduce mortality due to breast cancer. Additional efforts are needed to reach women, particularly black women and older women, with early screening methods such as mammography.