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Abstract

SummaryAlthough it has been demonstrated in previous studies that tubal ligation can have widespread effects on ovarian function, including a decrease in the risk of subsequent ovarian cancer, few studies have evaluated effects on breast cancer risk. In a population-based case-control study of breast cancer among women 20-54 years of age conducted in three geographic areas, previous tubal ligations were reported by 25.3% of the 2173 cases and 25.8% of the 1990 controls. Initially it appeared that tubal ligations might impart a slight reduction in risk, particularly among women undergoing the procedure at young ages (< 25 years). However, women were more likely to have had the procedure if they were black, less educated, young when they bore their first child, or multiparous. After accounting for these factors, tubal ligations were unrelated to breast cancer risk (relative risk (RR) = 1.09, 95% confidence interval (CI) 0.9-1.3), with no variation in risk by age at, interval since, or calendar year of the procedure. Subjects were asked to complete a month-by-month calendar documenting all contraceptive methods used since menarche. Pregnancies and other life events were first marked on the calendar to serve as a frame of reference for changes in contraceptive behaviour over time. Information recorded on the calendar regarding the occurrence of a tubal ligation was used to compute the age at, interval since, and calendar time of the procedure.Completed interviews were obtained from 2202 of the 2558 eligible cases (86.1%) and 2009 of the 2477 eligible controls (81.1%). Reasons for non-interview included subject refusals (6.4% in cases vs 14.0% in controls), death (0.4% vs 0.2%), illness (0.6% vs 0.2%), language problems (0.3% vs 1.4%), a move outside of the study area (0.6% vs 2.3%) and other miscellaneous reasons (0.2% vs 0.8%). In addition, physician consent for interview was denied for 5.4% of the cases. Among controls, an overall response rate of 73.4% was achieved through multiplication of the telephone screener and interview response rates. To assure comparability between the cases and controls, the 29 cases who indicated on interview that they did not have a residential telephone and the 19 controls with a history of breast cancer were eliminated, leaving 2173 cases and 1990 controls available for analysis.Since the median interval between diagnosis and interview was 87 days for cases, all information on risk factors, including that pertaining to tubal ligations, was truncated at the date of diagnosis for cases or the date at completion of the telephone screener for controls. The relationship of breast cancer risk factors to tubal ligation among the controls was assessed by calculating χ 2 statistics. The relationship of tubal ligation to breast cancer risk was assessed through calculation of odds ratios to approximate relative risks (RRs). Logistic regression analyses were used to obtain maximum likelihood estimates of RRs and their 95% confidence intervals (CI) (Breslow and Day, 1980). The significance of in...

Tubal ligation and incidence of 26 site-specific cancers in the Million Women Study

“…Reports of the relationship between tubal ligation and breast cancer risk have been varied, including suggestions of either a reduced ( Kreiger et al , 1999 ; Calle et al , 2001 ) or increased risk ( Irwin et al , 1988 ), although the majority of studies reported no significant association ( Brinton et al , 2000 ; Eliassen et al , 2006 ; Iversen et al , 2007 ; Dorjgochoo et al , 2009 ; Press et al , 2011 ; Gaudet et al , 2013 ; Nichols et al , 2013 ), consistent with our findings.…”