The significance of the amount of myometrial invasion in patients with Stage IB endometrial carcinoma

Abstract

Background: The 1988 International Federation of Gynecology and Obstetrics (FIGO) staging system for endometrial carcinoma defined Stage IB as disease with invasion of less than one-half of the myometrium, although most of the data on prognostic factors are based on invasion of the inner one-third, middle one-third, or outer one-third of the myometrium. The objective of this study was to determine whether the depth of myometrial invasion is correlated with outcome in patients with Stage IB endometrial carcinoma.

Methods: Between November, 1987 and June, 1998, 251 patients with Stage IB endometrioid adenocarcinoma of the uterus underwent simple hysterectomy followed by intravaginal brachytherapy. The depth of myometrial invasion was less than or equal to one-third (Group I) in 191 of 251 patients (79%) and greater than one-third to less than one-half (Group II) in 52 of 251 patients (21%). Comprehensive surgical staging (CSS) was done in 12% of patients. The two groups were balanced with regard to age (< 60 years vs. > or = 60 years), FIGO grade, lower uterine segment involvement (LUSI), CSS, and the use of postoperative external-beam radiation. The rate of capillary-like space invasion (CLSI), however, was 9% in Group I compared with 25% in Group II (P = 0.002). The median follow-up was 58 months.

Results: The overall 5-year actuarial local-regional control (LRC), disease free (DFS) survival, and overall survival (OS) rates were 95%, 92%, and 92%, respectively. These end points, however, did not vary significantly between the two groups. The 5-year LRC, DFS, and OS rates in Groups I and II were 96% versus 95%, respectively (P = 0.9); 92% versus 94%, respectively (P = 0.7); and 92% versus 90%, respectively (P = 0.5). On multivariate analysis, the influence on outcome of age, grade, amount of myometrial invasion, LUSI, and CLSI was evaluated. Only age > or = 60 years and FIGO Grade 3 were correlated with poor DFS (P = 0.02 and P = 0.03, respectively) and OS (P = 0.001 and P = 0.01, respectively).

Conclusions: Based on this study, in patients with Stage IB endometrial carcinoma, the amount of myometrial invasion, defined as invasion less than or equal to one-third of the myometrium versus invasion greater than one-third and less than one-half of the myometrium, did not appear to influence outcome. Age > or = 60 years and FIGO Grade 3, however, emerged as independent prognostic factors for poor DFS and OS.