Although removal of both ovaries is known to protect against subsequent development of ovarian cancer, the researchers believe their study shows premenopausal women should be advised that this benefit comes at the cost of an increased risk of cardiovascular disease and of other - more prevalent - cancers and higher overall mortality.
The study, the largest of its kind, compared women who were treated for a benign disease who had both ovaries removed, with those who had one or none removed.
The work looked at 113,679 cases of women aged 35-45 during the period April 2004 to March 2014. A third of the patients studied had both ovaries removed.
The research, ‘Removal of all ovarian tissue versus conserving ovarian tissue at time of hysterectomy in premenopausal patients with benign disease: study using routine data and data linkage’, published in the British Medical Journal, found that women who had one or no ovaries removed were less likely to develop ischaemic heart disease (coronary artery disease) or cancer after hysterectomy, than those who had both ovaries removed.
The researchers also found that fewer women who retained one or both ovaries died within the duration of the study – 0.6 per cent compared to 1.01 per cent.
“The combination of biological plausibility and the massive effect size make a compelling case that women can be advised that their risk of ovarian cancer is greatly reduced by surgical removal of both ovaries,” said Richard Lilford, Professor of Obstetrics and Gynaecology and Chair in Public Health at the University of Warwick’s Warwick Medical School, who led the study.
However, Lilford noted, the lifetime risk of developing ovarian cancer is one in 52 in the UK, and the removal of a metabolically active organ such as the ovary may have harmful effects in the long term. “If so, these long term disadvantages (combined with the unpleasant shorter term effects of acute oestrogen deprivation) must be offset against the benefit conferred by protection from ovarian cancer,” Lilford said.
A national database of hospital admissions in England was examined by the researchers and linked to the national register of deaths to conduct study. Unlike a previous, smaller study, the Nurses’ Health Study, it was conducted on a countrywide basis rather than in a sample, and examined associations between operation type, subsequent hospital admissions, and mortality.
Forty per cent of women with no specific risk factors for reproductive cancer had their ovaries removed during abdominal hysterectomy in the 35-45 age group.
Lilford said, “This might be a higher proportion than would be expected among women who were fully aware of the worse health outcomes with bilateral removal that we’ve reported. In that case, we might expect the proportion of women who select bilateral ovarian removal to decline as the health risks that must be traded for a reduced incidence of ovarian cancer come into sharper focus.”
The research team also found there was a decline, albeit a slow one, in the number of hysterectomies performed; nearly 9,000 women had a hysterectomy for a benign condition in the target age range in 2014, compared to almost 13,000 in 2004-05.