Verkasalo P K, Kaprio J, Pukkala E, Koskenvuo M
Department of Public Health, University of Helsinki, Finland.
Cancer Epidemiol Biomarkers Prev. 1999 Mar;8(3):271-4.
This population-based study investigated the occurrence of breast cancer over a 20-year period in a cohort of monozygotic (MZ) and dizygotic (DZ) twins in Finland. Altogether, 13,176 female twins of known zygosity who were living in Finland at the end of 1975 were identified from the Finnish Twin Cohort Study and followed-up for cancer through the Finnish Cancer Registry for the years 1976-1995. Standardized incidence ratios (SIRs) were calculated, based on national cancer incidence rates. The relative risk of breast cancer for MZ twins compared to DZ twins was decreased [SIR(MZ)/SIR(DZ) ratio = 0.78; 95% confidence interval (CI), 0.58-1.0]; the decreased risk for MZ twins (SIR = 0.76; 95% CI, 0.58-1.0) accounted for this result, whereas the risk for DZ twins did not differ from the general population risk (SIR = 0.98; 95% CI, 0.84-1.1). There was no risk decrease among MZ twins in other cancers related to reproductive behavior; i.e., number of children and age at first birth seem not to explain the decreased risk of breast cancer. Our results, which are in line with earlier studies on the same topic, suggest that prenatal influences or postnatal behavioral factors may protect MZ female twins from breast cancer.
这项基于人群的研究调查了芬兰单卵（MZ）和双卵（DZ）双胞胎队列在20年期间乳腺癌的发病情况。从芬兰双胞胎队列研究中识别出1975年末居住在芬兰的13176名已知合子性的女性双胞胎，并通过芬兰癌症登记处对她们在1976 - 1995年期间的癌症情况进行随访。根据全国癌症发病率计算标准化发病率（SIR）。与DZ双胞胎相比，MZ双胞胎患乳腺癌的相对风险降低了[SIR（MZ）/SIR（DZ）比值 = 0.78；95%置信区间（CI），0.58 - 1.0]；MZ双胞胎风险降低（SIR = 0.76；95% CI，0.58 - 1.0）导致了这一结果，而DZ双胞胎的风险与一般人群风险无差异（SIR = 0.98；95% CI，0.84 - 1.1）。在与生殖行为相关的其他癌症中，MZ双胞胎的风险没有降低；即子女数量和初产年龄似乎无法解释乳腺癌风险的降低。我们的结果与之前关于同一主题的研究一致，表明产前影响或产后行为因素可能保护MZ女性双胞胎免受乳腺癌侵害。
