Absolute depth of myometrial invasion in endometrial cancer is superior to the currently used cut-off value of 50%

ObjectiveIn endometrial carcinoma, myometrial invasion is a well known predictor of recurrence, and important in the decision making for adjuvant treatment. According to the FIGO staging system, myometrial invasion is expressed as invasion of < 50%> of the myometrium (50%MI). It has been suggested to use the absolute depth of invasion (DOI), or the tumor free distance to the serosa (TFD). The aim of this study was to compare DOI, 50%MI, and TFD.MethodsAll patients diagnosed with endometrioid endometrial carcinoma at the RUNMC, and the CWH from 1999 to 2009 were included. Histologic slides were reviewed for histologic type and grade, DOI, 50%MI, and TFD. After review, 335 patients were identified. DOI, 50%MI, and TFD were evaluated for their prediction of clinicopathologic characteristics.ResultsThe prediction of recurrence was best performed by DOI when compared to TFD, with an area under the ROC curve of 0.726, and 0.638 respectively. The optimal cut-off value for DOI was 4 mm. DOI independently correlated with recurrence of disease, and death of disease. TFD was associated with advanced age and large tumor diameter. DOI was the best predictor of progression-free and disease-specific survival next to 50%MI and TFD (HR 3.15, 95%CI 1.16–8.56) and (HR 10.35, 95%CI 1.23–86.93).ConclusionsDOI showed better predictive performance than TFD, and was more strongly correlated with clinicopathologic parameters than TFD and 50%MI. Possibly, DOI should substitute 50%MI as measure to express myometrial invasion in daily clinical practice. External validation is mandatory to confirm the proposed cut-off value of 4 mm.

► A comparison was made between three ways of assessing myometrial invasion
► Absolute Depth Of myometrial Invasion better correlates with prognostic parameters
► The best cut-off value for Absolute Depth Of myometrial Invasion is 4 mm.