Comparative analysis between the 8^th and 7^th AJCC as a prognostic tool for patients diagnosed with nonmetastatic head and neck soft-tissue sarcoma.

e23550 Background: Head and neck soft-tissue sarcoma (HN-STS) is a rare entity for which a new prognostic risk stratification has been proposed in the 8th AJCC. The tumor size 2cm and 4cm have been adopted as cutoffs for T1 to T3 classification and the invasion of surrounding structures denotes T4. In opposite, in the 7th edition the primary tumor size of 5 cm determines T1 and T2 classification. This study aimed to compare the 8th and 7th AJCC as a prognostic tool for HN-STS. Additionally, we sought to investigate prognostic factors in this group of patients. Methods: This is a single Tertiary Hospital study approved by the institutional ethical review committee from the AC Camargo Cancer Center. We retrospectively evaluated patients with non-metastatic HN-STS whose histology subtypes are included in the 40th chapter of the 8th AJCC version. We compared the AJCC 7th and 8th T staging with Cohen’s kappa coefficient using inter-rater agreement analysis. The Kaplan-Meier (KM) estimator was used to calculate median survival times; differences in time-to-event outcomes were assessed using the log-rank test. Cox proportional hazard model was used to assess the effect of features in overall survival (OS). Results: Ninety-five HN-STS treated with curative intent from 2005 from 2021 patients diagnosed were evaluated. Surgical resection (94.7%), radiotherapy (48.4%) and chemotherapy (23.1%) were the employed therapeutic approaches. Leiomyosarcoma and liposarcoma (10 of each subtype) were the most common histology subtypes; High grade disease was present in 66.3%. Kappa coefficient of inter-rater agreement was 0.46 with statistical significance (p = 0.03), which indicates poor agreement between AJCC 7th and 8th T staging system. Regarding OS stratified by T size in the AJCC 7th (T1 and T2) and 8th (T1, T2, T3 and T4) was not statistically different between groups (P = 0.83 and P = 0.21, respectively). Patients with T4 (47.6% vs 78.7%, P = 0.04) and high grade (64.0% vs 96.2%, P = 0.003) had worst 5-years OS. In Cox multivariate analysis, patients with 8th edition T4 and high grade had 3.15- and 4.16-fold increased risk of death, respectively. Conclusions: In our series of patients with HN-STS, neither 7th nor 8th AJCC T size category groups discriminated prognosis. Tumor with local invasion (8th AJCC T4) and high grade were all associated with increased risk of mortality.