Reproductive history and risk of colorectal cancer in postmenopausal women.

Abstract

Colorectal cancer is the fourth most common cancer and the second leading cause of cancer death in the United States, with approximately 142 570 new cases and 51 370 colorectal cancer-related deaths expected in 2010 (1). Observational and experimental evidence suggest that sex hormones, particularly estrogen, play a role in colorectal cancer pathogenesis (2). Most notably, a substantial body of epidemiological data supports an inverse relationship between postmenopausal oral hormone therapy use and the risk of colorectal cancer (3), an association that was confirmed by results of the Women's Health Initiative (WHI) Clinical Trial, which reported a statistically significant decreased risk of colorectal cancer among women using estrogen plus progestin formulations (but not among women using estrogen alone) compared with women using placebo (4,5).By contrast, two subsequent prospective studies reported a positive association between endogenous estrogen level and the risk of colorectal cancer in postmenopausal women. The first investigation, which was conducted in the WHI Observational Study, found that a high endogenous level of estrogen was associated with a 1.5-fold increased risk of developing colorectal cancer after adjustment for established colorectal cancer risk factors (6). Similarly, the New York University Women's Health Study reported a 60% increased risk of colorectal cancer for women in the highest quartile of circulating estrogen level compared with those in the lowest quartile (7). The positive associations between endogenous estrogen level and the risk of colorectal cancer reported by these investigations are consistent with laboratory data demonstrating the proliferative effects of exogenous estradiol in colorectal tissue and in colorectal cancer cell lines (8-11). The findings from these observational and experimental studies, when considered together with the data on hormone therapy use and colorectal cancer, suggest that endogenous and exogenous sex hormones may play different roles in colorectal tumorigenesis.

Colorectal Cancer Risk Associated with Reproductive Factors among Turkish Women

“…We did not find statistically significant associations between parity and the risk of CRC, but it was determined in our study that CRC risk decreased in women who had menarche at a later age (p>0.05). A similar decreasing trend was observed in previous studies [5,7,10,19].…”

“…Estrogen production before puberty could increase CRC cell numbers and cause DNA mutation therefore it is considered to be a risk factor for CRC [7,10]. We did not find statistically significant associations between parity and the risk of CRC, but it was determined in our study that CRC risk decreased in women who had menarche at a later age (p>0.05).…”

“…According to the Nurses' Health Study, which reported a statistically significant association between older age at first pregnancy or parity and risk of CRC. Most of the studies observed that older age at first pregnancy and number of parity was associated with risk of CRC [6,7,9,20,21].…”

“…Women were informed about the study by the researchers prior to study and the ones who agreed to participate were enrolled in the study. The data were collected by face-to-face interviews by using the data collection form that was prepared by the researchers by scanning the literature [2,[6][7][8][9][10][11][12][13][14][15] Participants were asked whether they had ever used OCC (no, yes) and the total number of years of use (categorized as months). We defined parity as the total number of pregnancies lasting 6 months or longer.…”

“…Besides, reproductive and hormonal factors, such as parity, age at birth of first child, age at menarche, and age at menopause, use of hormone therapy or oral contraceptive could be effective as well for lifetime exposure to endogenous estrogens [5][6][7][8][9][10][11][12]. CRC is one of the most treatable types of cancer when colorectal cancer is found at an early stage before it has spread.…”