Breast cancer risk and hysterectomy status: the Multiethnic Cohort study

Hysterectomy, bilateral oophorectomy, and breast cancer risk in a racially diverse prospective cohort study

BACKGROUND

Gynecologic surgery is hypothesized to reduce risk of breast cancer; however, associations may be modified by subsequent hormone use. Our objective was to examine the association between gynecologic surgery and breast cancer incidence considering the use of hormone therapy.

METHODS

The Sister Study is a prospective cohort of initially breast cancer-free women aged 35-74 years with a sister who had breast cancer. We used Cox proportional hazards models to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) for the association between gynecologic surgery (no surgery, hysterectomy only, bilateral oophorectomy with or without hysterectomy) and incident breast cancer among 50 701 women.

RESULTS

History of gynecologic surgery was common, with 13.8% reporting hysterectomy only and 18.1% reporting bilateral oophorectomy with or without hysterectomy. During follow-up (median = 11.4 years), 3948 cases were diagnosed. Compared with no surgery, bilateral oophorectomy was inversely associated with breast cancer (HR = 0.91, 95% CI = 0.83 to 1.00), and hysterectomy alone was positively associated (HR = 1.12, 95% CI = 1.02 to 1.23). Compared with no surgery and no hormone therapy, bilateral oophorectomy combined with estrogen only therapy (HR = 0.83, 95% CI = 0.74 to 0.94) was inversely associated with breast cancer, while hysterectomy combined with estrogen plus progestin therapy was positively associated with breast cancer (HR = 1.25, 95% CI = 1.01 to 1.55).

CONCLUSIONS

We observed an inverse association between bilateral oophorectomy and breast cancer risk. The positive association between hysterectomy and breast cancer may be due to concomitant estrogen plus progestin therapy.

Hysterectomy and Risk of Breast, Colorectal, Thyroid, and Kidney Cancer - an Australian Data Linkage Study

BACKGROUND

This study aimed to investigate the associations between hysterectomy for benign indications and risk of breast, colorectal, kidney, and thyroid cancer, and to explore whether these associations are modified by removal of ovaries at the time of surgery or by age at surgery.

METHODS

We conducted a retrospective cohort study of the female population of Western Australia (n = 839,332) linking data from electoral, hospital, births, deaths, and cancer records. We used Cox regression to estimate HRs and 95% confidence intervals (CI) for the associations between hysterectomy and diagnosis of breast, colorectal, kidney, and thyroid cancers.

RESULTS

Compared with no surgery, hysterectomy without oophorectomy (hysterectomy) and hysterectomy with bilateral salpingo-oophorectomy (hysterectomy-BSO) were associated with higher risk of kidney cancer (HR, 1.32; 95% CI, 1.11-1.56 and HR, 1.29; 95% CI, 0.96-1.73, respectively). Hysterectomy, but not hysterectomy-BSO, was related to higher risk of thyroid cancer (HR, 1.38; 95% CI, 1.19-1.60). In contrast, hysterectomy (HR, 0.94; 95% CI, 0.90-0.98) and hysterectomy-BSO (HR, 0.92; 95% CI, 0.85-1.00) were associated with lower risk of breast cancer. We found no association between hysterectomy status and colorectal cancer.

CONCLUSIONS

The associations between hysterectomy and cancer varied by cancer type with increased risks for thyroid and kidney cancer, decreased risk for breast cancer, and no association for colorectal cancer.

IMPACT

As breast, colorectal, and gynecologic cancers comprise a sizeable proportion of all cancers in women, our results suggest that hysterectomy is unlikely to increase overall cancer risk; however, further research to understand the higher risk of thyroid and kidney cancer is warranted.

A Multicentre Observational Study on Risk Factors for Breast Cancer

Background

Breast cancer is the most common malignancy in Indian women. There is scant data from Indian hospital-based populations on the prevalence of risk factors of this disease. We performed this study to quantify and analyze various epidemiological risk factors in Indian breast cancer patients.

Methods

This was a multicenter collaborative study wherein breast cancer patients older than 18 years were served a structured questionnaire after informed consent. Patients or their relatives were required to fill out the questionnaire and those who were unable to read and write were excluded. Data were abstracted from case record forms and variables were descriptively analyzed.

Results

Between January 2015 and February 2016, 800 patients were screened, of whom 736 patients with a mean age of 50.13 years were enrolled in the study. The mean number of pregnancies was 2.75 (0-11), the number (percentage) of women who had breastfed for more than 6 months was 628 (85.3) and 406 (55.1%) patients were post-menopausal at the time of breast cancer diagnosis. Of the enrolled patients, 91 (12.8%) had history of exposure to passive smoke, 13 (1.8%) had partners who were heavy smokers, 27 (3.7%) had history of oral contraceptive use, 4 (0.5%) had history of hormone replacement therapy, and 103 (14%) had undergone hysterectomy with oophorectomy.

Conclusion

Our study contributes to the descriptive prevalence of some known risk factors in Indian breast cancer patients.

Associations of Premenopausal Hysterectomy and Oophorectomy With Breast Cancer Among Black and White Women: The Carolina Breast Cancer Study, 1993-2001

Black women experience higher rates of hysterectomy than other women in the United States. Although research indicates that premenopausal hysterectomy with bilateral oophorectomy decreases the risk of breast cancer in black women, it remains unclear how hysterectomy without ovary removal affects risk, whether menopausal hormone therapy use attenuates inverse associations, and whether associations vary by cancer subtype. In the population-based, case-control Carolina Breast Cancer Study of invasive breast cancer in 1,391 black (725 cases, 666 controls) and 1,727 white (939 cases, 788 controls) women in North Carolina (1993-2001), we investigated the associations of premenopausal hysterectomy and oophorectomy with breast cancer risk. Compared with no history of premenopausal surgery, bilateral oophorectomy and hysterectomy without oophorectomy were associated with lower odds of breast cancer (for bilateral oophorectomy, multivariable-adjusted odds ratios = 0.60, 95% confidence interval: 0.47, 0.77; for hysterectomy without oophorectomy, multivariable-adjusted odds ratios = 0.68, 95% confidence interval: 0.55, 0.84). Estimates did not vary by race and were similar for hormone receptor-positive and hormone receptor-negative cancers. Use of estrogen-only menopausal hormone therapy did not attenuate the associations. Premenopausal hysterectomy, even without ovary removal, may reduce the long-term risk of hormone receptor-positive and hormone receptor-negative breast cancers. Varying rates of hysterectomy are a potentially important contributor to differences in breast cancer incidence among racial/ethnic groups.

The relationship between bilateral oophorectomy and plasma hormone levels in postmenopausal women

Oophorectomy prior to natural menopause reduces breast cancer risk. We evaluated whether timing of oophorectomy (during premenopause vs. postmenopause) or hysterectomy was associated with hormone levels, specifically estradiol, estrone, estrone sulfate, testosterone, sex hormone binding globulin (SHBG), dehydroepiandrosterone sulfate (DHEAS), and prolactin, using data from the Nurses' Health Study. We included 2,251 postmenopausal women not using hormones who provided blood samples in 1989-1990 and/or 2000-2002, and who were controls in various nested case-control studies. We used multivariate linear mixed-effects models to assess geometric mean hormone levels by surgery status. Bilateral oophorectomy was associated with 25% lower testosterone levels versus women with natural menopause (20.8 vs. 15.5 ng/dL) (P < 0.0001) with no effect of timing of surgery (P = 0.80). SHBG levels were lower among women with a premenopausal oophorectomy (52.2 nmol/L) versus those with natural menopause (58.1 nmol/L) or a postmenopausal oophorectomy (62.0 nmol/L) (P = 0.02). There was no significant association of oophorectomy with estradiol, estrone, estrone sulfate, DHEAS, or prolactin levels (P ≥ 0.23). A simple hysterectomy was associated with a significant 8% lower testosterone (P = 0.03) and 14 % lower DHEAS (P = 0.02) levels compared with women with natural menopause but not with other hormone levels. Although limited by small numbers, our findings suggest no differential influence of timing of surgery on sex hormone levels. The reduction of testosterone levels in women with oophorectomy or hysterectomy suggests a possible role of this hormone in postmenopausal breast cancer development.

Bilateral oophorectomy and risk of cancer in African American women

PURPOSE

African American women are more likely to undergo hysterectomy, with or without bilateral oophorectomy, at younger ages than white women. It is well established that women who have a bilateral oophorectomy at younger ages are at reduced risk of breast cancer, and there is some evidence of an increased risk of colorectal and lung cancer.

METHODS

Using data from 44,514 women in the Black Women's Health Study, we prospectively investigated the relation of hysterectomy and oophorectomy to incidence of breast, colorectal, and lung cancer and to mortality from cancer. Hazard ratios (HRs) and 95 % confidence intervals (CIs) were estimated using Cox proportional hazards regression with control for confounding factors.

RESULTS

During 16 years of follow-up, hysterectomy alone, relative to no hysterectomy, was not associated with risk of breast, lung, or colorectal cancer. Bilateral oophorectomy, relative to hysterectomy with ovarian conservation, was inversely associated with risk of estrogen receptor-positive (ER+) breast cancer (HR 0.62; 95 % CI 0.45-0.85) but not with ER-negative breast cancer; age at surgery and menopausal hormone use did not modify the associations. HRs for the association of bilateral oophorectomy with incidence of colorectal and lung cancer were nonsignificantly increased for women who had surgery before age 40 years and had used menopausal hormones for less than 2 years (HR 1.65; 95 % CI 0.73-3.73 for colorectal cancer and HR 1.71; 95 % CI 0.68-4.31 for lung cancer). Bilateral oophorectomy was not associated with cancer mortality.

CONCLUSIONS

Bilateral oophorectomy was associated with reduced risk of ER+ breast cancer regardless of age at surgery and use of menopausal hormones. There were nonsignificant increases in risk of colorectal and lung cancer for women with oophorectomy at younger ages and short duration of menopausal hormone use.

Invited commentary: reproductive organ surgeries and breast cancer risk--apples, oranges, or fruit cocktail?

Case-control and cohort studies are almost always complicated by nonrandom exposure allocation, which must be minimized in the design and analysis phases. Tubal sterilization is a common gynecological procedure that may be associated with other reproductive organ surgeries, which in turn may be associated with breast cancer risk. In this issue of the Journal, Gaudet et al. (Am J Epidemiol. 2013;177(6):492-499) argue successfully that tubal sterilization is unassociated with breast cancer risk. Scrutiny of the heterogeneous studies included in their meta-analysis underscores the role of confounding and effect modification in observational epidemiologic studies. Specifically, tubal sterilization is unassociated with breast cancer risk, but either oophorectomy or hysterectomy, or both, and the timing of these procedures warrant careful consideration in the design, analysis, and interpretation of observational research on reproductive factors.

Breast cancer risk and ovariectomy, hysterectomy, and tubal sterilization in the women's contraceptive and reproductive experiences study

Removal or impairment of ovaries before menopause may affect a woman's breast cancer risk by altering her cumulative exposure to ovarian hormones. The Women's Contraceptive and Reproductive Experiences Study, a population-based, multicenter case-control study of incident invasive breast cancer, recruited women aged 35-64 years (4,490 cases and 4,611 controls) who provided data on ovariectomy, hysterectomy, and tubal sterilization during in-person interviews. Controls were frequency-matched to cases by age, race, and study site. Unconditional logistic regression analysis was used. Women who had not undergone premenopausal reproductive surgery were the referent group. Bilateral ovariectomy was associated with reduced breast cancer risk overall (odds ratio (OR) = 0.59, 95% confidence interval (CI): 0.50, 0.69) and among women <45 years of age (ORs ranged from 0.31 to 0.52), but not among those who were older at surgery. It was also associated with a reduced risk for estrogen and progesterone receptor-positive tumors (OR = 0.63, 95% CI: 0.52, 0.75) but not receptor-negative tumors. Hysterectomy with ovarian conservation (OR = 0.83, 95% CI: 0.72, 0.96) and hysterectomy with partial ovary removal (OR = 0.73, 95% CI: 0.59, 0.91) were also associated with lower risk. No association with breast cancer risk was observed with tubal sterilization only or partial ovariectomy without hysterectomy. Reproductive organ surgeries may alter ovarian hormone levels, thereby affecting breast cancer risk.

Plasma sex hormone concentrations and breast cancer risk in an ethnically diverse population of postmenopausal women: the Multiethnic Cohort Study

To add to the existing evidence that comes mostly from White populations, we conducted a nested case-control study to examine the association between sex hormones and breast cancer risk within the Multiethnic Cohort that includes Japanese American, White, Native Hawaiian, African American, and Latina women. Of the postmenopausal women for whom we had a plasma sample, 132 developed breast cancer during follow-up. Two controls per case, matched on study area (Hawaii, Los Angeles), ethnicity/race, birth year, date and time of blood draw and time fasting, were randomly selected from the women who had not developed breast cancer. Levels of estradiol (E(2)), estrone (E(1)), androstenedione, dehydroepiandrosterone (DHEA), and testosterone were quantified by RIA after organic extraction and Celite column partition chromatography. E(1) sulfate, DHEA sulfate (DHEAS), and sex hormone-binding globulin (SHBG) were quantified by direct immunoassays. Based on conditional logistic regression, the sex hormones were positively associated and SHBG was negatively associated with breast cancer risk. All associations, except those with DHEAS and testosterone showed a significant linear trend. The odds ratio (OR) associated with a doubling of E(2) levels was 2.26 (95% confidence interval (CI) 1.58-3.25), and the OR associated with a doubling of testosterone levels was 1.34 (95% CI 0.98-1.82). The associations in Japanese American women, who constituted 54% of our sample, were similar to or nonsignificantly stronger than in the overall group. This study provides the best evidence to date that the association between sex hormones and breast cancer risk is generalizable to an ethnically diverse population.