Tubal sterilization and the risk of endometrial cancer

Tubal ligation and endometrial Cancer risk: a global systematic review and meta-analysis

BACKGROUND

Studies on relationship between tubal ligation and endometrial cancer have led to contradictory findings. In several studies, however, a reduced endometrial cancer risk was suggested following tubal ligation. Therefore, a systematic review and meta-analysis was conducted to examine the relationship between tubal ligation and endometrial cancer risk.

METHODS

In this systematic review and meta-analysis, PubMed/Medline, Web of Science, Scopus, Embase, and Google Scholar were searched for relevant studies published up to May 30th, 2018. We compared endometrial cancer risk in women with and without tubal ligation in retrieved studies.

RESULTS

Two hundred nine studies were initially retrieved from the data bases. After exclusion of duplicates and studies which did not meet inclusion criteria, ten cohort and case-control studies, including 6,773,066 cases, were entered into the quantitative meta-analysis. There was 0.90% agreement between two researchers who searched and retrieved the studies. The summary OR (SOR) was reported using a random effect model. Begg's test suggested that there was no publication bias, but a considerable heterogeneity was observed (I² = 95.4%, P = 0.001). We pooled the raw number of tables cells (i.e. a, b, c, and d) of eight studies. The SOR suggested that tubal ligation was significantly associated with a lower risk of endometrial cancer (SOR = 0.577, 95% CI = 0.420-0.792). Also, given the rare nature of endometrial cancer (< 5%), different effect sizes were considered as comparable measures of risk. Therefore we pooled ten studies and SOR of these studies revealed that tubal ligation was significantly associated with a lower risk of endometrial cancer (SOR = 0.696, 95% CI = 0.425-0.966). Besides that, we pooled eight studies in which adjusted effect sizes were reported and a subsequent analysis revealed that the summary estimate of adjusted odds ratio (SAOR) was significant (SAOR = 0.862, 95% CI = 0.698-1.026).

CONCLUSIONS

This study revealed a protective effect of tubal ligation on endometrial cancer risk (approximately 42% lower risk of cancer). It is recommended that studies should be designed to reveal mechanisms of this relationship.

Epidemiology of Endometrial Carcinoma: Etiologic Importance of Hormonal and Metabolic Influences

Endometrial carcinoma is the most common gynecologic cancer in developed nations, and the annual incidence is projected to increase, secondary to the high prevalence of obesity, a strong endometrial carcinoma risk factor. Although endometrial carcinomas are etiologically, biologically, and clinically diverse, hormonal and metabolic mechanisms are particularly strongly implicated in the pathogenesis of endometrioid carcinoma, the numerically predominant subtype. The centrality of hormonal and metabolic disturbances in the pathogenesis of endometrial carcinoma, combined with its slow development from well-characterized precursors in most cases, offers a substantial opportunity to reduce endometrial carcinoma mortality through early detection, lifestyle modification, and chemoprevention. In this chapter, we review the epidemiology of endometrial carcinoma, emphasizing theories that link risk factors for these tumors to hormonal and metabolic mechanisms. Future translational research opportunities related to prevention are discussed.

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

BACKGROUND

Tubal ligation is known to be associated with a reduction in ovarian cancer risk. Associations with breast, endometrial and cervical cancers have been suggested. We investigated associations for 26 site-specific cancers in a large UK cohort.

METHODS

Study participants completed a questionnaire on reproductive and lifestyle factors in 1996-2001, and were followed for cancer and death via national registries. Using Cox regression models, we estimated adjusted relative risks (RRs) for 26 site-specific cancers among women with vs without tubal ligation.

RESULTS

In 1 278 783 women without previous cancer, 167 430 incident cancers accrued during 13.8 years' follow-up. Significantly reduced risks were found in women with tubal ligation for cancers of the ovary (RR=0.80, 95% CI: 0.76-0.85; P<0.001; n=8035), peritoneum (RR=0.81, 0.66-0.98; P=0.03; n=730), and fallopian tube (RR=0.60, 0.37-0.96; P=0.04; n=168). No significant associations were found for endometrial, breast, or cervical cancers.

CONCLUSIONS

The reduced risks of ovarian, peritoneal and fallopian tube cancers are consistent with hypotheses of a common origin for many tumours at these sites, and with the suggestion that tubal ligation blocks cells, carcinogens or other agents from reaching the ovary, fallopian tubes and peritoneal cavity.

Tubal Ligation and Risk of Endometrial Cancer: Findings From the Women's Health Initiative

OBJECTIVE

Bilateral tubal ligation (BTL) is a common form of birth control in the United States. There are limited, contradictory data examining BTL and the risk of endometrial cancer and none examining type I and type II cancers separately. We investigated the association between BTL and endometrial cancer risk using the Women's Health Initiative (WHI) Observational and Dietary Modification Studies.

METHODS

Demographic information and history of BTL were obtained from the baseline questionnaires from 76,483 WHI participants in the Observational and Dietary Modification Studies. Univariable and multivariable models were used to examine the association of BTL with type I and type II endometrial cancers.

RESULTS

A total of 1137 women were diagnosed with incident endometrial cancer (972 type I and 128 type II) during a mean follow-up of 11.3 years. Overall, 14,499 (19%) women had undergone BTL. There were no statistically significant associations noted between BTL and age at BTL for type I or type II cancers.

CONCLUSIONS

We examined the largest patient cohort to date in an effort to determine the impact of BTL on endometrial cancer risk. In the WHI trial, we observed no overall effect of BTL on the risk of type I or type II endometrial cancer, suggesting that patients undergoing this popular birth control method likely do not have an associated change in their baseline risk for endometrial cancer.

The epidemiology of endometrial and ovarian cancer

This review highlights similarities in the epidemiology of endometrial and ovarian cancer, including highly correlated incidence rates and similar risk factor profiles. Factors that decrease risk for both cancers include a late menarche, early age at first birth, giving birth and breastfeeding, and use of oral contraceptives. Short or irregular cycles and late menopause are associated with increased risk for both. Other risk factors that appear to operate in a similar direction include decreased risk associated with IUD use or a tubal ligation, and increased risk associated with obesity, lack of exercise, and use of talc powders in genital hygiene. Estrogen excess is proposed as the underlying mechanism for most endometrial cancers, whereas incessant ovulation has been suggested as the explanation for ovarian cancer. However, an increased number of estimated ovulatory cycles correlates directly with risk for both endometrial and ovarian cancer, suggesting that reproductive tissue turnover with an accumulation of PTEN or p53 mutations represents a possible common mechanism. An immune-based explanation involving mucin proteins represents another common mechanism that could explain additional risk factors. Maintenance of ideal weight, breastfeeding children, use of oral contraceptives, and avoidance of talc powders in genital hygiene are measures that could lower the risk for both types of cancer. Careful selection of patients for prophylactic oophorectomy for those women who are coming to hysterectomy for benign disease is an additional measure to consider for ovarian cancer.

Molecular pathogenesis of endometrial and ovarian cancer

Pregnancy, breastfeeding, and oral contraceptive pill use interrupt menstrual cycles and reduce endometrial and ovarian cancer risk. This suggests the importance of turnover within Mullerian tissues, where the accumulation of mutations in p53 and PTEN has been correlated with number of cycles. The most common type of endometrial cancer (Type I) is endometrioid and molecular abnormalities include mutations in PTEN, KRAS and β-catenin. The Type I precursor is Endometrial Intraepithelial Neoplasia which displays PTEN defects. Type II endometrial cancer (whose precursors are less clear) includes serous and clear cell tumors and the most common alteration is p53 mutation. For ovarian cancer, histopathologic types parallel endometrial cancer and include serous, mucinous, endometrioid, and clear cell; some molecular features are also shared. The most frequent type of ovarian cancer is high grade serous that often displays p53 mutation and its precursor lesions may originate from normal-appearing fallopian tube epithelium that contains a p53 "signature". Mutations in KRAS, BRAF and PTEN are described in mucinous, endometrioid and low grade serous cancers and these may originate from ovarian cortical inclusion cysts. A consideration of molecular and other pathogenetic features, like epidemiology and histopathology, may provide a better understanding of endometrial and ovarian cancer.

Tubal sterilization, all-cause death, and cancer among women in the United Kingdom: evidence from the Royal College of General Practitioners' Oral Contraception Study

OBJECTIVE

The purpose of this study was to examine the relationship between tubal sterilization and subsequent all-cause death and the risk of any gynecologic and breast cancer in women in the United Kingdom.

STUDY DESIGN

A cohort study was conducted with 2801 sterilized women and 2801 nonsterilized women who were identified from the UK Royal College of General Practitioners' Oral Contraception Study. Adjusted hazard ratios and 95% CIs were calculated with Cox regression.

RESULTS

Tubal sterilization was not associated with significantly altered risks of subsequent all-cause death or cancer. Tubal sterilization was associated with a nonsignificant reduced risk of subsequent gynecologic (adjusted hazard ratio, 0.84; 95% CI, 0.52-1.37) and breast cancer (adjusted hazard ratio, 0.88; 95% CI, 0.67-1.16).

CONCLUSION

The absence of increased long-term death and cancer risk is reassuring, given that many women have chosen this method of contraception.

Tubal sterilization and risk of cancer of the endometrium

OBJECTIVE

Surgical sterilization is a common method of contraception among U.S. women. Most surgical sterilizations are tubal ligations, but few studies have investigated their potential impact on endometrial cancer risk.

METHODS

A case-control study included 405 women diagnosed with endometrial cancer at 5 U.S. medical centers between 1987 and 1990 and 297 age-, race-, and location-matched controls who were identified by random-digit-dialing. Questionnaires ascertained information on tubal sterilization, and logistic regression models generated odds ratios (ORs) to estimate relative risk.

RESULTS

The OR and 95% confidence interval for tubal sterilization, which was reported by 47 cases and 40 controls, was 0.9 (0.6-1.4) before adjustment and 1. 4 (0.8-2.4) after adjustment for age, parity, and oral contraceptive use. Age at surgery, years since surgery, or calendar years of surgery were not associated with endometrial cancer, and associations did not vary according to parity or stage of disease at diagnosis.

CONCLUSIONS

Tubal sterilization is not substantially associated with endometrial cancer.

Female sterilization. Evidence

The literature review herein reveals substantial information regarding the safety, efficacy, short-term complications, long-term complications, and noncontraceptive benefits of sterilization. This information should be helpful for providers and potential sterilization candidates. The review also reveals areas where the data are unclear. Points to keep in mind during counseling include the following: The vast majority of women are satisfied with the decision to undergo sterilization. The fact that regret occurs underscores the importance of counseling and adequate individual deliberation before the procedure. In addition to the difficulty and expense associated with sterilization reversal, the woman should thoroughly understand the permanence of the procedure. Although failure is a rare event, it can occur many years after the procedure. Although evidence suggests that hysterectomy rates are higher in sterilized women aged less than 30 to 35 years, it is unlikely that there is a plausible biologic effect of sterilization on hysterectomy risk. An association between tubal sterilization and menstrual cycle changes does not seem valid for changes noted up to 2 years after the procedure. Data are unclear and inconsistent among studies observing women more than 2 years after the procedure. Evidence consistently shows that sterilization is associated with a reduced incidence of ovarian cancer and pelvic inflammatory diseases. Most studies show no effect or improvement of sexual satisfaction after sterilization. Complications during and postprocedure are rare. Sterilization provides no protection against the acquisition of sexually transmitted disease. Patients and their physicians should recognize that sterilized women may need more targeted preventive efforts for health screening and to reduce high-risk behavior than women who use other contraceptive methods. The surgeon's experience and the woman's preferences should govern the ultimate decision regarding the approach and occlusion method. Level II-2 evidence indicates comparable safety between interval laparoscopy and minilaparotomy. Data consistently show that in experienced trained hands, tubal sterilization is safe and highly effective regardless of the approach or occlusive method. Attention to the subtleties of technique seems to be most important in ensuring procedure safety and efficacy. Reanalysis of the CREST data shows that the cumulative failure rate of bipolar coagulation is comparable with the failure rate of unipolar coagulation if a substantial length of tube is adequately coagulated. The data discussed herein can be used to guide management decisions that may increase accessibility and reduce cost of the procedure. Low-resource settings and office settings have maintained an excellent safety record for this procedure through performance of sterilization under local anesthesia. The use of local anesthesia enables a change in procedure location from an inpatient operating room to a free-standing surgical clinic or adequately equipped office. Local anesthesia, with or without preoperative medication, is an excellent option associated with a lower complication risk, reduced cost, and shorter, easier recovery. The surgeon should have specific training in the effective use of local anesthetics, preoperative medications, and management of rare complications in low-resource settings. Little additional research is needed regarding the safety and efficacy of standard sterilization approaches and occlusion methods. There is a need for continued development of nonsurgical methods of sterilization, microlaparoscopic approaches performed in the office setting, and the feasibility and acceptance of service provision by nonspecialist health care providers. The evidence indicates that female sterilization can be performed safely in a variety of resource settings ranging from rural sterilization camps in developing countries to high-tech, resource-rich operating rooms in developed c

Tubal ligation, menstrual changes, and menopausal symptoms

One of the problematic effects of tubal sterilization is menstrual changes or disorders, although the results of studies in this area have been inconsistent and inconclusive. Recently, there has been growing evidence that tubal sterilization protects against ovarian cancer, possibly through physiological transformations that result in ovarian dysfunction and decline. This report explores the possibility that the biological mechanism of ovarian dysfunction and decline may affect the menstrual and menopausal changes that result from hormonal imbalances. Using data from a homogeneous population of college alumnae assessed for health status, athletic history, and lifestyle characteristics, we focused on a premenopausal subgroup of women in the age range of 40-44 years and with at least one pregnancy. Multivariate analyses were performed to compare sterilized women (n = 56/516, 11%) in this subgroup with nonsterilized women (89%). The two groups were alike in mean age, mean parity, body mass index, smoking history, physical activity levels, and athletic status. Factors that significantly distinguished sterilized women from nonsterilized women were perimenopausal symptoms, such as flushing, sweating, breast pain, vaginal dryness, and pain associated with menstrual cycles.

Tubal ligation and risk of breast cancer

Although 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. The relationship of tubal ligations to risk did not vary according to the presence of a number of other risk factors, including menopausal status or screening history. Furthermore, effects of tubal ligation were similar for all stages at breast cancer diagnosis. Further studies would be worthwhile given the biologic plausibility of an association. However, future investigations should include information on type of procedure performed (since this may relate to biologic effects) as well as other breast cancer risk factors.