Uterine serous and grade 3 endometrioid carcinomas: is there a survival difference?

Serous components within endometrial carcinoma are reportedly poor prognosticators. However, to the authors' knowledge the percentage of tumors which must be comprised of a serous component in order to affect outcome is unknown. The authors compared overall survival (OS) in women with endometrial carcinomas comprised of various percentages of uterine serous carcinoma (USC) with that of women with International Federation of Gynecology and Obstetrics (FIGO) Grade 3 endometrioid carcinoma (G3EC) to determine whether outcomes varied between these two poorly differentiated histologies.

Data concerning women with either G3EC or USC who were diagnosed between January 1990 and November 2000 were collected retrospectively. Cases were reviewed to confirm diagnosis and estimate the fraction of tumor comprised of USC. Variables assessed included patient age and race, tumor stage, and lymphovascular space invasion. Associations between variables were tested using the Fisher exact test. The Kaplan-Meier method was used to evaluate OS with comparisons performed using the log-rank test.

Fifty-two women with G3EC and 87 women with USC were identified. The OS of women with tumors comprised of > 50% USC was found to be significantly worse compared with women with G3EC (hazard ratio [HR] of 2.4; 95% confidence interval [95% CI], 1.2-5.2). Women with USC were more likely to present with extrauterine disease (odds ratio of 2.2; 95% CI, 1.1-4.5). The 5-year survival rate for women with G3EC was 75% compared with 41% for women with tumors that were > 50% USC (P = 0.01). There was a significant trend toward a worse OS in women with even 10% USC compared with women with G3EC.

USC involving > 50% of an endometrial carcinoma was found to be predictive of worse OS compared with the OS of women with G3EC. In patients with early-stage disease, a trend toward a worse prognosis was found to exist when USC comprised even 10% of a tumor. Investigation into the treatment of endometrial carcinoma should include and document tumors with any percentage comprised of USC.