Classification and regression tree (CART) analysis of endometrial carcinoma: Seeing the forest for the trees

Abstract

Objective: The objectives of the study are to evaluate which clinicopathologic factors influenced overall survival (OS) in endometrial carcinoma and to determine if the surgical effort to assess para-aortic (PA) lymph nodes (LNs) at initial staging surgery impacts OS.

Methods: All patients diagnosed with endometrial cancer from 1/1993-12/2011 who had LNs excised were included. PALN assessment was defined by the identification of one or more PALNs on final pathology. A multivariate analysis was performed to assess the effect of PALNs on OS. A form of recursive partitioning called classification and regression tree (CART) analysis was implemented. Variables included: age, stage, tumor subtype, grade, myometrial invasion, total LNs removed, evaluation of PALNs, and adjuvant chemotherapy.

Results: The cohort included 1920 patients, with a median age of 62 years. The median number of LNs removed was 16 (range, 1-99). The removal of PALNs was not associated with OS (P=0.450). Using the CART hierarchically, stage I vs. stages II-IV and grades 1-2 vs. grade 3 emerged as predictors of OS. If the tree was allowed to grow, further branching was based on age and myometrial invasion. Total number of LNs removed and assessment of PALNs as defined in this study were not predictive of OS.

Conclusion: This innovative CART analysis emphasized the importance of proper stage assignment and a binary grading system in impacting OS. Notably, the total number of LNs removed and specific evaluation of PALNs as defined in this study were not important predictors of OS.

Keywords: CART analysis; Classification and regression tree analysis; Endometrial cancer; Lymph nodes; Overall survival; Staging.

Figure 1

Kaplan-Meier analysis demonstrating no difference in overall survival for patients with para-aortic nodes removed (P=0.450).

Figure 2

Kaplan-Meier analysis for the optimal classification and regression tree subgroups. Five-year overall survival rates were: 90.9% (95% CI: 88.6-92.7%) for stage I patients, 82.6% (95% CI: 76.2-87.4%) for stage II-IV & grade 1/2 patients, and 46.9% (95% CI: 40.6-52.9%) for stage II-IV & grade 3 patients.

Figure 3

Classification and regression tree results using the following variables: age, stage, tumor subtype, grade (G), myometrial invasion (Myo Inv), total lymph nodes removed, and evaluation of para-aortic lymph nodes. Complexity parameter (CP) =0.022 for the green highlighted tree; CP=0.0071 for the tree shown. The numerators indicate number of deaths, and the denominators indicate total number of cases in the subcategory.