Ovarian cancer risk is known to be reduced amongst women who have had children, but reported associations with breastfeeding are varied. Few studies have had sufficient power to explore reliably these associations by tumour histotype. In a prospective study of 1.1 million UK women, 8719 developed ovarian cancer during follow-up. Cox regression yielded adjusted relative risks (RRs) overall and by tumour histotype amongst women with different childbearing patterns. Nulliparous women had a 24% greater ovarian cancer risk than women with one child, with significant heterogeneity by histotype (p = 0.01). There was no significant increase in serous tumours, a modest increase in mucinous tumours, but a substantial increase in endometrioid (RR = 1.49, 95% CI: 1.18-1.89) and clear-cell tumours (RR = 1.68, 1.29-2.20). Among parous women, each additional birth was associated with an overall 6% reduction in ovarian cancer risk; this association also varied by histotype (p = 0.0006), with the largest reduction in risk for clear-cell tumours (RR per birth = 0.75, 0.65-0.85, p
Journal article
Int J Cancer
15/01/2018
142
281 - 289
breastfeeding, histological type, ovarian cancer, parity, reproductive factors, Adenocarcinoma, Clear Cell, Adenocarcinoma, Mucinous, Adult, Breast Feeding, Cystadenocarcinoma, Serous, Endometrial Neoplasms, Female, Follow-Up Studies, Humans, Middle Aged, Ovarian Neoplasms, Parity, Pregnancy, Prognosis, Prospective Studies, Young Adult