The significance of the degree of myometrial invasion in patients with Stage IB endometrial cancer

Objective: To study the validity of the FIGO staging classification of endometrial cancer Stage IB by correlating degree of myometrial invasion depth with outcome measures. Study Design: Fifty patients with endometrial adenocarcinoma FIGO Stage IB who underwent hysterectomy between 1989 and 2001 were divided into two groups according to depth of myometrial invasion. The first group comprised of 31 patients with myometrial invasion of less than or equal to one-third. The second group included 19 patients with invasion greater than one-third but less than one-half. The two groups were compared with regard to prognostic factors and outcome measures. Results: The overall 5-year recurrence-free survival, disease specific survival and overall survival rates were 87%, 94% and 77%, respectively. These outcome measures did not vary significantly between the two groups. There were no statistically significant differences between the two groups with regard to the following parameters: duration of follow-up, age, proportion of patients who underwent complete surgical staging and postoperative adjuvant radiotherapy. Histologic parameters of the two groups, such as histological type, grade and proportion of patients with capillary space-like involvement and lower uterine segment involvement were not significantly different. Conclusions: In patients with Stage IB endometrial cancer the amount of myometrial invasion defined as less than one third compared with invasion greater than one third does not appear to correlate with their outcome, thus validating the FIGO staging system.