Colorectal cancer in northeast Italy: reproductive, menstrual and female hormone-related factors.

The role of reproductive and menstrual factors and a few medical conditions linked to female hormones in the aetiology of colorectal cancer was investigated in a case-control study conducted in Pordenone province in northeastern Italy, on 89 women with colorectal cancer and 148 controls admitted to hospital for a wide spectrum of acute, non-digestive nor neoplastic disorders. After adjustment for age and social class, parous women, as compared to nulliparous ones, were significantly protected against colorectal cancer (odds ratio, OR = 0.4, [95% confidence interval, CI:0.2-0.8]) and the risk appeared to decrease with successive pregnancies up to five or more (0.2, [0.04-0.6]). Compared to women who had their first birth at age 24 or less, the OR for those who had it at 30 or older was 2.0, but the inverse trend in risk was not significant. However, among parous women only, age at first birth, but not parity, seemed to retain a certain influence. Late age at menopause seemed to decrease colorectal cancer risk (OR for menopause at age greater than or equal to 50 vs. less than 45 = 0.4, [0.2-1.0] chi 2(1) (trend) = 3.66). Conversely, age at last birth, number of abortions, years between marriage and first birth, age at menarche, pattern of menstrual cycle and occurrence of a few medical conditions potentially linked to female hormones were similarly reported by cases and controls. Due to the very limited number of oral contraceptive (OC) users (9 controls but only 1 case), and the lack of oestrogen replacement therapy users, the influence of exogenous female hormones on colorectal cancer could not be analysed meaningfully.