Objective: Our aim was to estimate the number of women in Japan in whom ovarian cancer could be prevented by performing prophylactic oophorectomy.
Methods: Of 1289 women who were diagnosed clinically and histologically as having primary cancers of the ovary between 1986 and 1995, 53 (4.1%) had undergone hysterectomy with conservation of one or both ovaries. Clinical data and representative microscopic slides for these 53 cases were evaluated.
Results: Hysterectomy had been performed at the age 45 or above in 28 of the 53 patients (53%). We estimated that performance of prophylactic oophorectomy in women who underwent a hysterectomy at age 45 or older would prevent 2.2% (4.1% x 0.53) of the cases of ovarian cancer in Japan, which is below the 3.3% estimated for women in other countries. The interval between the hysterectomy and the diagnosis of ovarian cancer ranged from 1 to 29 years (mean 9.9 years). Fourteen patients (26%) developed ovarian cancer within 5 years of the hysterectomy. The overall 3-year survival rate of these 53 patients was 65%, not significantly different from that for patients with ovarian cancer in the national study in Japan.
Conclusions: Prophylactic oophorectomy for the prevention of ovarian cancer in Japanese women would appear to have a lesser impact than reported in other industrialized nations. The short interval between hysterectomy and the diagnosis of ovarian cancer observed in 26% of the patients suggested that ovarian cancer can develop within a few years of the visualization of apparently normal ovaries.