Relationship between tamoxifen use and high risk endometrial cancer histologic types.

OBJECTIVES: We wished to determine whether a pre-existing diagnosis of breast cancer or the use of tamoxifen among patients with pre-existing breast cancer influences the histologic type of subsequently diagnosed endometrial carcinoma, the interval between these diagnoses, or survival.
METHODS: A single institution retrospective review was performed of all patients who underwent primary surgery for endometrial carcinoma from 1995-2005. We compared the histologic type of endometrial carcinoma among patients with a prior history of breast cancer to those without. Patients with a previous diagnosis of breast cancer were further analyzed by comparing histologic type, progression-free and overall survival between tamoxifen users and non-users.
RESULTS: Among 732 women with endometrial carcinoma, 59 patients (8%) had a previous diagnosis of breast cancer, of whom 29 (49%) had used tamoxifen. Women with a history of breast cancer were more likely to have a high risk uterine histologic type (grade 3 endometrioid, papillary serous, or clear cell) (18/59; 31%) than those without this prior malignancy (120/670, 18%; p=0.024). Breast cancer survivors whose endometrial carcinoma was of a high risk histologic type had a longer median duration of prior tamoxifen use compared to those with lower risk histologic types (60 versus 46 months, p=0.034).
CONCLUSIONS: Among women with endometrial carcinoma, those with a history of breast cancer are more likely to harbor a high risk uterine histologic subtype. Tamoxifen use of at least 60 months is associated with high risk uterine histologic subtypes when compared to no tamoxifen use. This study adds to existing data suggesting a relationship between tamoxifen use and development of endometrial carcinoma of more aggressive histologic types.