Role of Goiter and of Menstrual and Reproductive Factors in Thyroid Cancer: A Population-based Case-Control Study in New Caledonia (South Pacific), a Very High Incidence Area

Abstract

Exceptionally high incidence rates of thyroid cancer have been reported for Melanesian women in New Caledonia (South Pacific). To investigate the occurrence of thyroid cancer in that country and to clarify the role of goiter and hormonal factors in that disease in women, a countrywide population-based case-control study was conducted in 1993-1999. The study included 293 cases, identified through pathology registers and whose thyroid cancer was verified histologically, and 354 population controls. Thyroid cancer was associated with goiter, age at menarche, irregular menstruation, and hysterectomy. There was a dose-response trend with number of full-term pregnancies (p = 0.01), with an odds ratio of 2.2 (95% confidence interval: 1.1, 4.3) for women with eight or more pregnancies. Miscarriage, particularly as an outcome of the first pregnancy, was also indicated as a risk factor. The association between voluntary abortion and thyroid microcarcinoma could be explained by enhanced medical surveillance and improved cancer detection in women undergoing abortion. Oral contraceptives and hormone replacement therapy were unrelated to thyroid cancer. The very high birth rate among Melanesian women in New Caledonia, as well as late age at menarche, may explain, in part, their elevated incidence of thyroid cancer.

Time trends and geographic variations for thyroid cancer in New Caledonia, a very high incidence area (1985–1999)

“…In a previous study conducted by Ballivet et al (1995), the incidence rate reported in 1985-1992 for Melanesian women was 34.9 per 100,000, the highest incidence figure ever reported. No clear explanation is currently available for this elevated incidence, although we have shown that it may be partly accounted for a high parity and other reproductive factors that are common in Melanesian women of New Caledonia (Truong et al, 2005). In order to provide clues on potential etiologic factors of thyroid cancer, the incidence was examined in this paper over an extended study period (1985)(1986)(1987)(1988)(1989)(1990)(1991)(1992)(1993)(1994)(1995)(1996)(1997)(1998)(1999).…”

Differentiated Thyroid Carcinoma Risk Factors in French Polynesia

“…Despite two case-control studies performed in China (Preston-Martin et al, 1993) and New-Caledonia (Truong et al, 2005) evidenced, as we did, an increased risk in women who were everpregnant, two cohort studies, performed in China (Wong et al, 2006) and Japan (Pham et al, 2009), did not evidence such an increased risk, and another performed in Thailand, although based on 17 cases showed a decreased risk (Sungwalee et al, 2013). Results in other populations are heterogeneous (Peterson et al, 2012) and this heterogeneity does not seem to be attributable only to differences in number of children between studied populations.…”

Obesity and thyroid cancer

“…In 1979, considering the follow-up of 600 patients, Cady et al (1979) observed that women who had thyroid cancers before menopause presented with less aggressive tumors, in comparison with women diagnosed after menopause. Several subsequent studies with large cohorts have proven a strong association of thyroid diseases and, more specifically, thyroid cancers with female gender; in addition, many reports describe differences in thyroid cancer comportment in men and women (McTiernan et al 1984, Ron et al 1987, Galanti et al 1996, Truong et al 2005, Leux et al 2012. But how do estrogen and/or reproductive hormones influence thyroid cancers?…”