Cancer Incidence Rates in Eddy and Lea Counties

New Mexico, 1970-1994

Breast Cancer (Female)

Breast cancer is the leading cancer among women in the US and in New Mexico. In New Mexico in 1993, breast cancer was three times more common than the next most commonly diagnosed cancer in women (lung) (Figure 1).

Risk factors for breast cancer include a family history of breast cancer; hormonal factors such as early age at menarche, late age at menopause, never giving birth or breastfeeding, first giving birth at a late age, and exposure to estrogen (such as in oral contraceptives or therapies related to menopause); poor dietary habits including low vegetable consumption; social factors such as higher education and socioeconomic level; and exposure to ionizing radiation (NCI 1993; ACS 1995; Mettler 1995).

Nationally, incidence rates of invasive breast cancer have increased over the last two decades, from approximately 82.4 per 100,000 in 1973 to 109 in 1990 (NCI 1993). However, this rise has not been steady, with a spike around 1974, another large increase between 1980 and 1987, and falling rates from 1988 to 1990. In New Mexico, incidence rates of breast cancer were slightly lower than, or comparable to, US rates, increasing from approximately 68 per 100,000 in 1971 to 92 in 1993 (Figure 16). Like US rates, statewide rates also fell, but began a few years later, in 1991.

Spatial Variation

Spatial variation of incidence rates for breast cancer, for the period between 1970 and 1992, among females residing in New Mexico, Eddy County, and Lea County, is presented in Table 17.

Non-Hispanic Whites: During the period studied, the statewide incidence rate of breast cancer among non-Hispanic white females was 94.0 per 100,000 statewide, and ranged from a low of 24.6 in Mora County to a high of 134 in Rio Arriba County. Breast cancer incidence rates among non-Hispanic white females residing in Eddy and Lea counties were below this statewide rate. In both counties, breast cancer incidence rates were higher among non-Hispanic white females than among Hispanic white females.

Hispanic Whites: During the period studied, the statewide incidence rate of breast cancer among Hispanic white females was 56.8 per 100,000 statewide, and ranged from a low of 30.0 in De Baca County to a high of 91.0 in Los Alamos County. The breast cancer incidence rate among Hispanic white females residing in Lea County was below the statewide rate.

Temporal Variation

Temporal variation of incidence rates for breast cancer, for the period between 1970 and 1994, among females residing in Eddy County and Lea County is presented in Figures 17 and 18. Females: Statewide, breast cancer incidence rates increased overall during the period studied, from approximately 68 per 100,000 in 1971 to 92 in 1993, but began to level off in 1990, and fall in 1991. In Eddy County, breast cancer incidence rates increased from approximately 72 per 100,000 in 1971 to 97 in 1993, and were comparable in magnitude to, and generally followed the pattern of, statewide rates. In Lea County, breast cancer incidence rates did not substantially change overall between 1970 and 1994, did not follow the pattern of statewide rates, and were close to one-half the magnitude of statewide rates. Incidence rates of breast cancer varied widely among females in both counties during the period studied.

By Ethnicity: Statewide, breast cancer incidence rates appear to have increased among non-Hispanic white females, from approximately 83 per 100,000 in 1971 to 109 in 1993, and among Hispanic white females, from approximately 40 per 100,000 in 1971 to 75 in 1993. Rates among non-Hispanic whites were higher than rates among Hispanic whites during the entire study period, and comparable to US rates. Rates among both ethnic groups appear to follow the statewide pattern. County-level breast cancer incidence rates were more variable during the study period (especially for Hispanic whites). In Eddy County, breast cancer incidence rates among non-Hispanic white females increased during the period studied, from approximately 68 per 100,000 in 1971 to 105 per 100,000 in 1993. Incidence rates of breast cancer among Hispanic white females residing in Eddy County decreased overall during the period studied, from approximately 80 per 100,000 in 1971 to 65 per 100,000 in 1993, but fluctuated widely, so that a clear downward trend was not obvious. In Lea County, breast cancer incidence rates among Hispanic whites also varied widely, jumping from approximately 4 per 100,000 in 1980 to 65 per 100,000 in 1990. Breast cancer incidence rates among non-Hispanic whites residing in Lea County increased overall during the period studied, from approximately 50 per 100,000 in 1971 to 55 per 100,000 in 1993, but varied for individual years between 1970 and 1994.

Factors Affecting Rates: A spike in SEER (national) breast cancer incidence rates in 1974 have been suggested to have been related to the publicity surrounding the breast cancer surgeries of several prominent women (NCI 1993). The increase may also have been due to increases in early diagnosis resulting from the use of mammography screening. Cancers which normally would have been diagnosed during this period with techniques other than mammography may have been diagnosed earlier with mammography.