Comorbidity Burden and Survival After Primary Surgery for Oral Cavity Squamous Cell Carcinoma: Tumor Stage as an Effect Modifier.

Background/

Objectives

To evaluate the association between comorbidity burden, quantified using the Charlson Comorbidity Index (CCI), and overall survival (OS) and disease-free survival (DFS) in patients treated surgically for oral cavity squamous cell carcinoma (OCSCC), and to determine whether this association is modified by tumor stage.

Methods

We retrospectively analyzed 325 patients treated with primary surgery for OCSCC at a single institution (2009-2021). CCI was scored excluding the index malignancy component and evaluated as a continuous variable. Univariate and multivariable Cox proportional hazards models assessed the association between CCI and OS/DFS, including a formal CCI × stage interaction term. Kaplan-Meier curves stratified by CCI (>4 vs. ≤4) were generated separately in early- and advanced-stage subgroups and compared by log-rank test.

Results

CCI was significantly associated with OS (HR 1.14 per point, 95% CI 1.04-1.25, p = 0.005) but not DFS (HR 1.02, 95% CI 0.92-1.12, p = 0.768). A significant CCI × stage interaction was observed (HR 0.82, 95% CI 0.68-0.99, p = 0.036): within early-stage patients, an elevated CCI (>4) was associated with a significantly worse 5-year OS (52.9% vs. 72.3%, p = 0.009), whereas no such difference was observed in advanced-stage patients (40.9% vs. 42.6%, p = 0.56).

Conclusions

The comorbidity burden was associated with overall but not disease-free survival after surgery for OCSCC. The association differed by tumor stage and was most apparent in early-stage disease. A recurrence-based classification of deaths showed that non-cancer death accounted for a substantially larger share of mortality among early-stage than advanced-stage patients, supporting a competing-mortality mechanism; independently adjudicated cause-of-death data were not available to confirm this directly. CCI may provide additional prognostic information in early-stage OCSCC.