Cancer Incidence Rates in Eddy and Lea Counties

New Mexico, 1970-1994

Leukemia

Leukemia is a group of cancers originating in bone marrow and spreading to the blood, and often to other areas of the body, including the liver, spleen, and lymph nodes (Cotran et al. 1994). In 1994 in New Mexico, 147 cases of newly diagnosed leukemia were reported, accounting for 2.2% of all cancers (NMTR 1996).

Adults are more likely to develop leukemia than children (NCI 1993). However, while leukemia accounts for only about 2.5% of all cancers diagnosed annually in the US, leukemia represents about 30% of all cancers diagnosed in children under 15 years of age. In addition, males in the US are diagnosed with leukemia more often than females. Risk factors for leukemia include genetic disorders such as Down's, Klinefelter's, and Bloom's syndromes; exposure to ionizing radiation; exposure to certain chemicals including benzene; cigarette smoking; and exposure to the adult T-cell leukemia/lymphoma virus. These factors, however, may account for only a small percentage of all leukemia.

Nationally, leukemia incidence rates did not substantially change over the last two decades, except for a slight drop from 10.2 per 100,000 in 1989 to 9 in 1990 (NCI 1993). In New Mexico, leukemia incidence rates were similar to US rates and changed only slightly overall during the period studied, from approximately 9 per 100,000 in 1971 to 9.5 in 1993 (Figure 25).

Spatial Variation

Spatial variation of incidence rates for leukemia, for the period between 1970 and 1992, among residents of New Mexico, Eddy County, and Lea County, is presented in Tables 24, 25 and 26.

Non-Hispanic Whites: During the period studied, the incidence rate for leukemia among non-Hispanic white males and females combined was 11.0 per 100,000 statewide, and ranged from a low of 6.4 in Union County to a high of 20.3 in Harding County. Among non-Hispanic white males in Eddy and Lea counties, leukemia incidence rates were below corresponding statewide rates. The incidence rate of leukemia among non-Hispanic white females in Eddy County was 9.9 per 100,000 (the tenth highest county rate among non-Hispanic white females in New Mexico). The incidence rate of leukemia among non-Hispanic white females in Eddy County was also higher than the incidence rate among non-Hispanic white females in Lea County (5.1 per 100,000).

Hispanic Whites: During the period studied, the incidence rate for leukemia among Hispanic white males and females combined was 7.2 per 100,000 statewide, and ranged from a low of 2.1 in Hidalgo County to a high of 24.8 in Harding County. The leukemia incidence rate among Hispanic white females in Eddy County was 9.3 per 100,000 (the seventh highest county rate among Hispanic white females in New Mexico).

Temporal Variation

Temporal variation of incidence rates of leukemia, for the period between 1970 and 1994, among residents of Eddy County and Lea County is presented in Figures 26 and 27.

By Sex: Statewide, leukemia incidence rates during the period studied increased among males, from approximately 10.5 per 100,000 in 1971 to 12.5 in 1993, and decreased among females, from approximately 8 per 100,000 in 1971 to 7 in 1993. In Lea County, leukemia incidence rates were comparable in magnitude to statewide rates and did not change substantially during the period studied. Incidence rates among both sexes residing in Lea County followed a similar pattern. In Eddy County, incidence rates of leukemia were more variable during the period studied, falling overall for males (during 1973 and 1985) and for females.

By Ethnicity: Statewide, leukemia incidence rates during the period studied increased slightly among Hispanic whites, from approximately 6 per 100,000 in 1971 to 8 in 1993, but decreased slightly among non-Hispanic whites, from approximately 11 per 100,000 in 1971 to 10 in 1993. Leukemia incidence rates among non-Hispanic whites were higher than those among Hispanic whites during the study period, and appear to determine the magnitude and fluctuation of county-level rates for all ethnicities combined. In Eddy County, leukemia incidence rates for non-Hispanic whites decreased over the period studied from approximately 17 per 100,000 in 1971 to 10 in 1993. Rates for Hispanic whites were more variable, with peaks around 1977 and 1984, and no cases of leukemia reported for several of the years studied. In Lea County, leukemia incidence rates for non-Hispanic whites began and ended the study period at approximately 10 per 100,000, but varied slightly for intervening years. Rates for Hispanic whites in Lea County were more variable, with a peak in 1973 and no cases of leukemia reported for several of the years studied.