Urothelial carcinoma risk drops with number of full-term pregnancies

Women who have given birth more than once are at lower risk of developing urothelial carcinoma (UC) compared with those who are uniparous, a study suggests.

Researchers looked at a cohort of 333,919 women (mean age at baseline, 51 years) from the European Prospective Investigation into Cancer and Nutrition. They identified 529 UC cases (median age, 68 years) over a median follow-up of 15 years, of which 80 were low grade, 233 were high grade, and 216 had unknown tumour grade. The tumours were aggressive in 230 of the cases, nonaggressive in 146, and unknown in 153.

In Cox proportional hazards models, a higher number of full-term pregnancies was protective against incident UC (≥5 vs 1: hazard ratio [HR], 0.48, 95 percent confidence interval [CI], 0.25–0.90; p_trend=0.010). On the other hand, there was a positive association between menopausal hormone therapy use and UC risk (vs nonuse: HR, 1.27, 95 percent CI, 1.03–1.57), but no dose response by years of hormone use was observed.

The estimates were independent of smoking status. Sensitivity analyses in never smokers showed a similar protective association between the number of full-term pregnancies and UC risk, whereas no association was seen for menopausal hormone therapy.

Overall, the associations were consistent across tumour aggressiveness and tumour grade subgroups.

Finally, menopausal hormone therapy was associated with an increased risk of nonmuscle-invasive urothelial carcinoma.

More studies are needed to shed light on the putative protective effects of parity and establish the role of perinatal hormonal changes, specifically how these changes may affect oestrogen receptor and progesterone receptor levels and urothelial cells in the bladder, according to the researchers.