Although extremely early-stage oral squamous cell carcinoma (OSCC) is generally associated with favorable primary outcomes, recurrence remains a major clinical challenge. Survival after recurrence is highly heterogeneous, and standardized post-recurrence risk stratification is lacking. The prognostic significance of host-related factors, particularly nutritional deterioration after recurrence, has not been systematically evaluated.

This retrospective study analyzed post-recurrence survival in 106 patients with extremely early-stage OSCC who developed recurrence. Overall survival was defined from recurrence to death or censoring. Post-recurrence nutritional change was assessed using body mass index change. Multivariable Cox models were applied after feature selection. A parsimonious prognostic model was internally validated, and risk stratification was evaluated using Kaplan–Meier analysis. Interaction analyses explored effect modification across clinical subgroups.

The median follow-up after recurrence was 48.95 months. Post-recurrence BMI change and vascular invasion were the strongest predictors of survival after recurrence. The model showed good discrimination and calibration, with time-dependent AUCs of 0.979 for 3-year survival and 0.925 for 5-year survival, along with clear survival separation among risk groups (log-rank P < 0.001). The adverse prognostic impact of BMI decline was consistent across subgroups, whereas age-related risk varied by pathological and metabolic characteristics.

Post-recurrence survival in extremely early-stage OSCC is strongly influenced by host-related nutritional deterioration. Monitoring BMI change may support individualized risk stratification and post-recurrence supportive care.