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Stage migration and prognostic refinement of oral squamous cell carcinoma under the AJCC 8th edition staging system:
Jianing Cui1,2, Qianrui Liu1,2, Hongshi Cai1,2
1Department of Oral and Maxillofacial Surgery, Hospital of Stomatology, Guanghua School of Stomatology, Sun Yat-Sen University, Guangzhou, China.
Objective:
The eighth edition of the American Joint Committee on Cancer (AJCC) staging system incorporated pathologic depth of invasion (pDOI) and pathologic extranodal extension (pENE) for prognostic stratification in oral squamous cell carcinoma (OSCC). However, the extent of stage migration and the consistency of survival discrimination across populations remained controversial. This study aimed to evaluate stage migration associated with the AJCC 8th edition, assess its prognostic performance relative to the AJCC 7th edition, and explore potential refinements to the pT classification.
Methods:
Patient data from the Hospital of Stomatology, Sun Yat-sen University (2014-2021), and the SEER database (2018-2019) were used. Overall survival (OS) and disease-specific survival (DSS) were estimated using the Kaplan-Meier method to compare the prognostic outcomes of the AJCC 7th and 8th editions. An exploratory refinement of the AJCC 8th pT classification was then developed using the SYSU-OSCC cohort. Multivariable Cox regression was used to assess the prognostic value of different cutoff thresholds, and a refined pT classification was proposed. Model performance was evaluated according to the established Groome criteria.
Results:
In the SYSU-OSCC cohort, upstaging was observed in 31.3% of patients for pT classification, 10.9% for pN classification, and 31.4% for overall pathologic stage. Compared with the AJCC 7th edition, the AJCC 8th showed clearer prognostic separation between pT3 and pT4a in the SYSU-OSCC cohort (5-year OS rates: 69.2% vs. 51.7%, p = 0.012; 5-year DSS rates: 76.6% vs. 62.0%, p = 0.014) and improved survival discrimination, particularly at intermediate and advanced-stage disease. However, prognostic overlap persisted between pT1 and pT2 categories (5-year OS rates: 82.4% vs. 76.9%, p = 0.14; 5-year DSS rates: 87.0% vs. 83.9%, p = 0.45). In the SEER-OSCC cohort, however, risk separation between pT3 and pT4a remained limited (3-year OS rates: 58.1% vs. 54.3%, p = 0.16; 3-year DSS rates: 64.5% vs. 63.4%, p = 0.41). Based on the SYSU-OSCC cohort, tumors with pDOI > 5 mm and ≤ 10 mm and a tumor size ≤ 2 cm were proposed for reclassification into the pT1 category. In the SYSU-OSCC training and internal validation cohorts, the exploratory refined classification showed improved prognostic performance compared with the original AJCC 8th edition.
Conclusion:
The AJCC 8th edition improved prognostic stratification in OSCC, particularly for intermediate and advanced-stage disease. However, residual prognostic overlap remained between specific pT categories. The exploratory refinement of selected pT thresholds may modestly improve prognostic accuracy. However, rigorous validation in larger independent external cohorts is required before its clinical applicability can be determined.
