Highlights
Key Findings from the AJCC Version 9 Proposal
The proposed staging system introduces several critical shifts in how salivary gland carcinoma (SGC) is classified. First, it replaces the traditional lymph node (LN) size-based staging with a quantitative count of positive nodes and the presence of extranodal extension (pENE). Second, the study validates a unified approach that applies equally to both major and minor salivary glands, addressing a long-standing gap in head and neck oncology. Finally, the proposed stage groupings (I-IV) demonstrate superior prognostic separation and a more balanced distribution of patients compared to the current Version 8 protocols.
Background: The Need for Specificity in Salivary Gland Malignancy
Salivary gland carcinomas represent a remarkably heterogeneous group of malignancies, encompassing over 20 distinct histologic subtypes with varying biological behaviors. Historically, the staging of these tumors has often been grouped with other head and neck sites or has relied on nodal staging criteria derived from squamous cell carcinomas. However, the clinical progression of SGC is distinct. For clinicians, the current American Joint Committee on Cancer (AJCC) and Union for International Cancer Control (UICC) eighth edition staging has been criticized for its lack of prognostic precision, particularly regarding nodal involvement. The drive toward a version nine classification stems from the need for a unified, SGC-specific system that can better inform treatment decisions, such as the necessity for postoperative radiotherapy or systemic therapy.
Study Design and Methodology
To address these limitations, a retrospective prognostic cohort study was conducted using a robust multi-institutional data set. The primary cohort was derived from the National Cancer Database (NCDB) and included 8,409 patients who underwent surgical treatment for major SGC between 2012 and 2017. The researchers focused on overall survival (OS) as the primary endpoint. To ensure the findings were generalizable, the proposed model was validated against an international cohort of 1,015 patients with major SGC and a specialized cohort of 444 patients with minor SGC from Memorial Sloan Kettering Cancer Center (MSKCC). The statistical analysis utilized Cox proportional hazards multivariable models to identify the most significant prognostic factors, specifically evaluating the impact of the number of pathologically positive lymph nodes and the presence of pathologic extranodal extension (pENE).
The Shift to Quantitative Nodal Assessment
Redefining pN Classification
The most significant change in the proposed Version 9 is the transition in the pN (pathologic node) classification. Analysis of the NCDB data revealed that the absolute count of positive lymph nodes is a more reliable predictor of survival than the size or laterality of the nodes. The study found that while one to three positive nodes without pENE had a relatively similar prognostic impact, the hazard ratio increased significantly once the count exceeded three. Additionally, pENE was confirmed as a potent independent predictor of poor outcomes. Based on these findings, the proposed pN classification is simplified:
pN1:
1 to 3 positive lymph nodes without pENE.
pN2:
More than 3 positive lymph nodes or the presence of pENE. This simplified binary approach not only improved the model fit, as evidenced by a lower Akaike Information Criterion (AIC) compared to the current system, but also provides a clearer roadmap for clinicians in the postoperative setting.
Key Results: Validating the Prognostic Shift
The results from the NCDB dataset were compelling. For the 7,659 patients with M0 disease, the 5-year overall survival was 87.2% for those with pN0 disease. This dropped to 68.2% for patients with a single positive node and plummeted to 41.4% for those with pENE-positive nodes. Multivariable analysis confirmed that the risk of death was 1.7 to 2.4 times higher for patients with positive nodes compared to those with pN0 disease. The proposed stage groupings were structured as follows:
Stage I:
T1N0.
Stage II:
T2N0.
Stage III A:
T1-2N1 or T3-4N0.
Stage III B:
T1-2N2 or T3-4N1-2.
Stage IV:
M1 (metastatic disease). The adjusted hazard ratios for these stages showed clear, incremental increases in the risk of mortality, providing clinicians with a more accurate tool for risk stratification. Notably, the C-index for the proposed classification remained high at 0.792, and the model fit was superior to the eighth edition.
Clinical Implications for Major and Minor Salivary Glands
One of the most impactful aspects of this research is the validation of the system across different anatomical sites. Historically, minor salivary gland carcinomas (those occurring in the palate, tongue, or buccal mucosa) have been staged using the criteria for the specific anatomical site of origin (e.g., oral cavity staging). This study demonstrates that the SGC-specific system performs exceptionally well for minor SGCs as well. By unifying the staging of all SGCs regardless of their primary site, the AJCC Version 9 proposal simplifies the diagnostic process and ensures that patients with minor SGC receive a prognosis based on the biology of the tumor rather than just its location.
Expert Commentary and Limitations
The transition to Version 9 represents a significant step toward precision medicine in head and neck oncology. By emphasizing nodal count and pENE, the staging system aligns with the biological reality that the volume of nodal disease and its invasive characteristics are the primary drivers of regional recurrence and distant metastasis. However, some experts note that while overall survival is a robust endpoint, it can be influenced by non-cancer-related deaths, particularly in an older patient population. Furthermore, while the system is applicable across various histologies, the specific behavior of high-grade vs. low-grade tumors still requires careful clinical consideration beyond the TNM stage alone. The study’s reliance on the NCDB also means that certain variables, such as disease-specific survival or specific recurrence patterns, were not available for all patients.
Conclusion: A New Standard of Care
The proposed Version 9 AJCC/UICC staging for salivary gland carcinoma provides a more accurate, evidence-based framework for patient management. By shifting the focus to quantitative nodal burden and extranodal extension, it offers superior prognostic discrimination and a more balanced distribution of patients across stages. As this system is adopted into clinical practice, it will likely lead to better-informed discussions between physicians and patients, more standardized clinical trials, and ultimately, improved survival outcomes through more targeted therapeutic interventions.
References
1. Huang SH, Cotler J, Palis B, et al. Proposed Version Nine of the AJCC and UICC TNM Classification for Salivary Gland Carcinoma. JAMA Otolaryngol Head Neck Surg. Published online February 12, 2025. doi:10.1001/jamaoto.2025.5396. 2. Amin MB, Greene FL, Edge SB, et al., eds. AJCC Cancer Staging Manual. 8th ed. Springer; 2017. 3. Lydiatt WM, Patel SG, O’Sullivan B, et al. Staging Head and Neck Cancers: Introduction to the Eighth Edition AJCC Cancer Staging Manual. CA Cancer J Clin. 2017;67(2):122-137.
