[Clinicopathological features of endometrial carcinoma in tamoxifen- and toremifene-treated breast cancer patients].

Objective: Estrogen is involved in the development of breast and endometrial cancers, and tamoxifen, an antiestrogen, is associated with an increased risk of endometrial cancer. Recently, tamoxifen use is suggested to be associated with the development of aggressive endometrial tumors. We performed a retrospective study to clarify the effects of tamoxifen (TAM) and toremifene (TOR) on clinicopathological features of endometrial cancer subsequently developed in breast cancer patients.

Methods: Endometrial cancer patients diagnosed at our institution from 2000 through 2008 were studied.

Results: Of 194 patients with endometrial cancer, 18 (9.3%) developed breast cancer before endometrial cancer diagnosis. Mean age was 66 years, and the median time interval between breast and endometrial cancer diagnosis was 10 years (range, 1.5 -32 years). Nine patients developed aggressive tumors(serous, clear cell, small cell carcinoma, and carcinosarcoma), and the remaining nine developed endometrioid tumor. Patients with aggressive tumor had a lower 5-year disease-specific survival (0% vs 88%, p<0.01). Ten patients had used TAM and/or TOR, and six had not; aggressive tumors developed in six of 10 TAM/TOR users, and in one of six nonusers (p=0.15), and the 3-year disease-specific survival rate was not different between TAM/TOR users and nonusers (62% vs 53%, p=0.84). Time intervals from breast cancer and endometrial cancer diagnosis were 10-16 years for TAM users and 5-6 years for TOR users (p=0.02).

Conclusion: Tamoxifen/toremifene use for breast cancer did not affect the prognosis of subsequent endometrial cancer in our small study; however, further studies were warranted. The use of toremifene may be associated with a shorter interval from breast cancer to endometrial cancer diagnosis compared to tamoxifen.