Challenging AJCC 8 Staging for Soft Tissue Sarcoma Using the NCDB

Abstract

Purpose: To determine whether the new American Joint Committee on Cancer (AJCC) 8 grouping of soft tissue sarcoma (STS) with nodal disease (N1M0) and metastatic disease (M1) as stage IV correctly represents the prognosis of these previously separate patient groups, using the National Cancer Database.

Methods and materials: Adults with STS identified in the 2004 to 2014 National Cancer Database, classified by the World Health Organization 2013 system into 10 histologic subgroups, were grouped according to AJCC 8 staging and analyzed according to demographic characteristics, histology, primary site, disease extent, and adjuvant treatment. Primary retroperitoneal sites, "other/unusual" histologic subgroups, and those with delays in therapy (>180 days from diagnosis) were excluded. We used χ² tests, Cox proportional hazard models, and propensity-score matched analyses.

Results: Of 82,987 patients identified, 55,417 met inclusion criteria; 29,855 (53.9%) were male, and 25,262 (46.1%) were female. Median age was 60 years (range, 18-90 years). Overall survival (OS) of STS of all sites was significantly different between N1M0 and N0-1M1 patients at 5 years (34.4%; [95% confidence interval {CI}, 30.1%-38.8%] vs 10.1% [95% CI, 9%-11%], respectively) and 10 years (27.3% [95% CI, 22.5%- 32.2%] vs 5.4% [95% CI, 4.5%-6.5%], respectively; log-rank test, P < .001). For STS of trunk and extremities in N1M0 and N0-1M1 patients, the N1M0 cohort was associated with significantly greater OS on multivariate Cox proportional hazards models (hazard ratio, 0.48; 95% CI, 0.41-0.58; P < .001), and this OS difference remained significant for propensity-matched cohorts of all primary sites (HR, 0.53; 95% CI, 0.44-0.64; P < .001).

Conclusions: In adult STS, including those of the trunk and extremity, OS is superior with N1M0 compared with N0-1M1 disease. These results suggest that the AJCC 8th edition grouping of N1 and M1 patients into stage IV may obscure the more favorable prognosis of patients with N1M0 disease.