An Evaluation of the Eighth Edition of the American Joint Committee on Cancer (AJCC) Staging System for Retroperitoneal Sarcomas Using the National Cancer Data Base (NCDB): Does Size Matter?

Objectives: Retroperitoneal sarcomas (RPS) are often large at diagnosis calling into question the seventh edition AJCC size classification of <5 cm (T1) or ≥5 cm (T2). The eighth edition expands T stage into 4 categories (T1: ≤5 cm, T2: 5<x≤10 cm, T3: 10<x≤15 cm, T4: >15 cm). We evaluated the prognostic ability of the eighth edition using the National Cancer Database (NCDB).

Methods: Patients with RPS treated between 1998 and 2011 were identified from the NCDB; overall survival (OS) was compared.

Results: Of the 6427 patients identified, 9% had tumors ≤5 cm (n=580), 19.4% 5<x≤10 cm (n=1246), 20.2% 10<x≤15 cm (n=1298) and 47.4% >15 cm (n=3045). With the eighth edition, stage II patients (G2/3 ≤5 cm) have a similar OS to stage IIIA patients (G2/3 5 cm<x≤10 cm), and patients with larger tumors (stage IIIB, G2/3>10 cm) show a decrease in OS. Tumor size as a continuous variable had a modest effect on survival (HR, 1.004; P=0.04). On multivariate analysis, higher T-stage was associated with decreased OS (T4 HR, 1.3; P<0.001) but high grade and incomplete resection (R2) were stronger prognostic factors. The c-index for both editions were similar (80.13 eighth vs. 80.08 seventh).

Conclusions: The eighth edition AJCC staging system for retroperitoneal sarcoma incorporates larger tumor size parameters that better characterize most patients, but tumor size alone is only a modest predictor of outcome.