Cancer Incidence Rates in Eddy and Lea Counties

New Mexico, 1970-1994

Thyroid Cancer

Thyroid cancer is relatively uncommon in the US (NCI 1993). In 1994 in New Mexico, 110 new cases of in situ and invasive thyroid cancer were reported, accounting for just 1.7% of all cancers.

Women are diagnosed with thyroid cancer over two times as frequently as men (NCI 1993). Exposure to ionizing radiation is a well-documented risk factor for thyroid cancer. Others may include reproductive and hormonal factors, a history of benign thyroid disease, and consumption of certain seafoods.

Nationally, thyroid cancer incidence rates increased slightly over the last two decades, from 3.6 per 100,000 in 1973 to 4.6 in 1990 (NCI 1993). In New Mexico, incidence rates of thyroid cancer were generally higher than US rates, and also increased slightly, from approximately 4.7 per 100,000 in 1971 to 5.4 in 1993 (Figure 46).

Spatial Variation

Spatial variation of incidence rates for thyroid cancer, for the period between 1970 and 1992, among residents of New Mexico, Eddy County, and Lea county, is presented in Tables 41, 42 and 43.

Non-Hispanic Whites: During the period studied, the incidence rate for thyroid cancer among non-Hispanic white males and females combined was 4.6 per 100,000 statewide, and ranged from a low of no cases in Guadalupe and Harding counties to a high of 11.6 in Mora County. The thyroid cancer incidence rate among non-Hispanic white females in Eddy County was 9.3 per 100,000 (the sixth highest county rate among non-Hispanic white females in New Mexico). Thyroid cancer incidence rates for non-Hispanic white females in Eddy and Lea counties were higher than for non-Hispanic white males: 9.3 vs. 2.5 in Eddy County and 3.1 vs. 0.9 in Lea County.

Hispanic Whites: During the period studied, the thyroid cancer incidence rate among Hispanic white males and females combined was 5.4 per 100,000 statewide, and ranged from a low of no cases in Catron and Harding counties to a high of 13.4 in Hidalgo County. Thyroid cancer incidence rates for Hispanic white females in Eddy and Lea counties were higher than for Hispanic white males: 7.1 vs. 0.5 in Eddy County and 4.6 vs. no incidence in Lea County.

Temporal Variation

Temporal variation of incidence rates for thyroid cancer, for the period between 1970 and 1994, among residents of Eddy County and Lea County is presented in Figures 47 and 48.

By Sex: Statewide, thyroid cancer incidence rates during the period studied increased among males, ranging from a low of approximately 2 per 100,000 in 1987 to a high of 4 in 1975. Incidence rates among females residing in New Mexico did not change substantially overall from 1970 to 1994; however, rates varied for intervening years, from a low of approximately 5.5 per 100,000 in 1988 to a high of over 8 in 1993. In addition, incidence rates among females peaked several times, including highs of approximately 8 per 100,000 in 1978, 7.5 in 1985, and 7.7 in 1991. In general, statewide thyroid cancer incidence rates among females were higher than among males by more than two times. In Eddy County, incidence rates of thyroid cancer among both sexes began and ended the study period at the same value (approximately 6 per 100,000 for females and approximately 2 per 100,000 for males), but varied widely for individual years. Incidence rates among males residing in Eddy County ranged from a low of no cases for several years to a high of approximately 4 per 100,000 between 1984 and 1986. Incidence rates among females residing in Eddy County ranged from a low of no cases for several years to a high of approximately 16 per 100,000 in 1984. In addition, incidence rates among females residing in Eddy County followed patterns similar to statewide rates, peaking around 1977, 1984, and 1991. In Lea County, incidence rates of thyroid cancer decreased during the study period for females, from approximately 5 per 100,000 in 1971 to 1 in 1993, and few cases for males were reported.

By Ethnicity: Statewide, thyroid cancer incidence rates increased slightly during the study period among non-Hispanic whites, from approximately 4.7 per 100,000 in 1971 to 5.5 in 1993, and among Hispanic whites, from approximately 5.0 per 100,000 in 1971 to 6 in 1993. Statewide rates were higher among Hispanic whites than among non-Hispanic whites. Thyroid cancer incidence rates among Hispanic whites varied widely, with no cases reported for many of the years studied. In Eddy County, thyroid cancer incidence rates among non-Hispanic whites began and ended the study period at approximately 4 or 5 per 100,000, but varied widely for the intervening years. In Lea County, thyroid cancer incidence rates among non-Hispanic whites decreased slightly during the period studied, from approximately 3 per 100,000 in 1971 to 1.5 in 1993.