A This question should be decided case by case despite new findings concluding that ovarian conservation until the age of 65 improves survival among women with benign disease.
It only seems that this controversy is coming to the fore for the first time. In reality, it has been hotly debated for decades. One camp favors oophorectomy to prevent ovarian cancer; the other, preservation of the ovaries to reduce the risk of heart disease and hip fracture.
What is the function of the postovulatory ovary?
GUZICK: Some experts recommend conserving the ovaries to reduce the risk of heart disease. Why? The postovulatory ovary continues to produce androgens, which are converted to circulating estrogens. The androgens themselves are said to improve libido (itself a controversial assertion),1 and their conversion to estrogens may reduce the risk of heart disease2 and hip fracture.3
Parker and colleagues used a Markov decision-analysis model to estimate whether, on balance, the ovaries should be removed or conserved during hysterectomy for benign disease in women at least 40 years old. Using this model, ovarian conservation averted enough heart disease and hip fracture cases to more than offset new cases of ovarian and breast cancers.
About half of all women older than 40 will die of heart disease,4 while fewer than 1% will die of ovarian cancer.5 If women undergoing hysterectomy for benign disease are roughly 50 times more likely to die of heart disease than ovarian cancer, then clearly even a small protective effect of ovarian conservation on heart disease will outweigh the potential for ovarian cancer.
For the moment, let’s take the study by Parker and colleagues at face value. Given the high base rate of cardiovascular disease, it is not surprising that oophorectomy markedly diminishes the overall probability of survival at age 80 among women undergoing hysterectomy at age 50 to 54. The authors estimate that oophorectomy reduces this probability from 62% to 54%. Moreover, the estimated impact of oophorectomy on mortality varies by age. This effect is built into the model because of the age-associated increase in the base rate of ovarian cancer mortality and the estimate that the risk of coronary heart disease declines 6% each year oophorectomy is delayed after menopause.6
Significant differences in survival curves between groups of women undergoing ovarian removal or conservation are found between the ages of 40 and 54, and the curves converge after age 65. Thus, Parker and colleagues conclude that “ovarian conservation until age 65 benefits long-term survival.”
Other factors may influence survival
GUZICK: Ovarian conservation reduces hip fracture3 but increases breast cancer, at least up until age 50.6 Such factors are included in the Parker analysis, but the main drivers of the model are heart disease and ovarian cancer. The conceptual framework for the model, and the pattern of the results, are clear strengths of this study.
MENZIN: Parker et al noted that their study did not address the benefits of oophorectomy among women with known or possible hereditary predisposition to ovarian cancer. Nevertheless, being aware of this major risk factor and its relevance to an informed consent discussion of hysterectomy is important, especially given the recognized benefits of risk-reducing surgery in this setting.
For women whose risk of ovarian cancer is equivalent to that of the general population, the decision is more complex. Hysterectomy, even with ovarian conservation, itself appears to reduce the risk of ovarian cancer by 10% to 40%—probably because abnormal-appearing ovaries are usually removed at hysterectomy.7,8 The prognosis of ovarian cancer in conserved ovaries appears equivalent to that in women without hysterectomy,9 although several studies suggest that 5% to 15% of ovarian cancers might have been prevented by oophorectomy at the time of prior hysterectomy for benign disease.
Why the Parker findings can’t be taken at face value
GUZICK: The estimated benefit of ovarian conservation in regard to heart disease was based on data acquired between 1976 and 1982 from the Nurses’ Health Study (NHS).2 This is problematic for several reasons. First, the relative risk of 2.2 was estimated in the NHS for coronary heart disease events, not deaths.2 It is not clear how Parker et al converted relative risk of events to relative risk of deaths, but apparently the risk estimate for events was applied to a baseline death rate. If so, then, because not all women with a cardiovascular event from 1976 to 1982 died of cardiovascular disease, the effect of oophorectomy is overstated.