Menstrual Factors, Reproductive History, Hormone Use, and Urothelial Carcinoma Risk: A Prospective Study in the EPIC Cohort

Reproductive Factors in the Risk of Bladder Cancer and Upper Urinary Tract Cancer: The Japan Public Health Center-Based Prospective Study

BACKGROUND

Reproductive factors are hypothesized to play a role in the incidence of bladder cancer and upper urinary tract cancer (UUTC, together, urothelial cancer). However, evidence regarding these associations is limited, particularly in Asian populations.

METHODS

We analyzed data from 55,882 females ages 40 to 69 years, and performed Cox proportional hazards regression analyses with three types of adjustment, namely age; reproductive factor of interest and covariates in addition to age (conventional model); and other reproductive factors in addition to the multivariable adjusted model (reproductive model).

RESULTS

During an average of 20.2 years of follow-up, 194 urothelial cancer cases (145 bladder cancer cases and 49 UUTC cases) were identified. Early age at natural menopause (<44 years, compared with 49-51 years) increased bladder cancer risk in the reproductive model (HR, 2.09; 95% CI, 1.04-4.20). An association between urothelial cancer/bladder cancer and age at menopause, including both natural and surgical/induced, was significant in the reproductive model (HR, 1.74; 95% CI, 1.09-2.77; and HR, 1.94; 95% CI, 1.15-3.28, respectively). Early age at natural menopause was suggested to increase urothelial cancer risk in the reproductive model (HR, 1.78; 95% CI, 0.93-3.42).

CONCLUSIONS

Our findings suggest a significant association between age at menopause and incidence of urothelial cancer/bladder cancer among Asian populations. This study aids understanding the role of reproductive factors in urothelial cancer/bladder cancer incidence.

IMPACT

In Japanese populations, age at menopause is suggested to be associated with urothelial cancer/bladder cancer incidence, especially regarding early natural menopause.

The Inequality of Females in Bladder Cancer

Urinary bladder cancer is worldwide one of the most diagnosed and costly types of cancer. One puzzle in the bladder cancer diagnosis is the disproportional relationship between genders. Males are more likely to be diagnosed with bladder cancer whereas females typically are diagnosed with more adverse disease and worse prognosis, which has led to speculation of the potential role of sex hormones and their receptors in this disease. Estrogen receptors are present in the human bladder, and their role in bladder cancer oncogenesis is increasingly becoming a focus for researchers around the world. This mini-review aims to give a brief overview of the status of female bladder cancer, and to which extend the sex hormones receptors play a role in this. A literature search was performed and included all female original studies on bladder cancer and hormone receptors. Estrogen-receptor alpha seems to be anti-oncogenic whereas estrogen-receptor beta is exhibiting its function pro-oncogenic. The receptor functions may be exercised through mRNA transcriptions and enzymes. Epidemiological studies indicate a potential increase in incidence of bladder cancer for females with earlier age at menopause, and clinical trials are investigating Tamoxifen as a potential treatment in bladder cancer. Increasing evidence supports the theory of bladder cancer development and progression as being partly hormone-dependent. This can lead to a change in conceptual background of bladder cancer etiology and development in the future. Further studies are required to more precise map the use of anti-hormonal drugs in the treatment of this cancer.