The December edition of ‘Eyes on Evidence’, the free monthly e-bulletin from NHS Evidence covering major new evidence as it emerges with an explanation about what it means for current practice, includes an expert commentary on new evidence from a large prospective study, using data from the European Prospective Investigation into Cancer and Nutrition (EPIC), examining the associations of oral contraceptive use and reproductive factors with ovarian cancer risk. The study reported that women who used oral contraceptives for 10 or more years had a 45% lower risk compared with users of ≤1 year. The researchers concluded that the study shows a strong protective association of oral contraceptives and parity with ovarian cancer risk.

According to the expert commentary "Many studies have shown the association between oral contraceptive use, pregnancy and reduced risk of epithelial ovarian cancer. This, the largest prospective study, confirms these findings and also reveals the increased risk associated with a late menopause. Equally, the duration of oral contraceptive use impacts on the protective effect, in that, the highest protection occurs with 10 years or more use. There is however, protection even with a single year usage. One action of combined oral contraceptives (like pregnancy), is the cessation of ovulation – which fits the long standing theory that a woman's risk of ovarian cancer is proportional to the number of ovulatory cycles during her lifetime. However further research is required to identify what in fact is affording protection – cessation of ovulation alone or some other hormonal effect? In order to develop a proper preventative strategy these questions require addressing".

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