Comparison of the 7th and 8th version of the AJCC classification system for soft tissue sarcomas of extremities and trunk in patients with localised, intermediate or high-grade disease treated at European tertiary sarcoma centres

Abstract

Background: The updated 8th version of the AJCC-staging system for soft tissue sarcomas (STS) has been criticised for omitting tumour depth as category-defining variable and eventually not improving prognostic accuracy in comparison to the 7th version. This study aimed at investigating the prognostic accuracy of both AJCC-versions in STS-patients treated at European tertiary sarcoma centres.Methods: 1032 patients (mean age: 60.7 +/- 16.3 years; 46.0% [n = 475] females; median follow-up: 38.6 months), treated at five tertiary sarcoma centres for localised, intermediate or high-grade STS of extremities and trunk were retrospectively included. Uni- and multivariate Cox-regression models and Harrell's C-indices were calculated to analyse prognostic factors for overall survival (OS) and assess prognostic accuracy.Results: In univariate analysis, prognostic accuracy for OS was comparable for both AJCC-versions (C-index: 0.620 [8th] vs. 0.614 [7th]). By adding margins, age, gender, and histology to the multivariate models, prognostic accuracy of both versions could be likewise improved (C-index: 0.714 [8th] vs. 0.705 [7th]). Moreover, tumour depth did not significantly contribute to prognostic accuracy of the 8th version's multivariate model (C-index for both models: 0.714). Stratification into four main T-stages based on tumour size only, as implemented in the 8th version, significantly improved prognostic accuracy between each category. However, T-stages as defined in the 7th version had poorer discriminatory power (C-index: 0.625 [8th] vs. 0.582 [7th]).Conclusion: Both AJCC-versions perform equally well regarding prognostic accuracy. Yet, simplification of the 8th version by omitting tumour depth as T-stage-defining parameter, whilst emphasizing the importance of tumour size, should be considered advantageous. (C) 2021 Elsevier Ltd, BASO similar to The Association for Cancer Surgery, and the European Society of Surgical Oncology. All rights reserved.