S2 Fig -

Disease-specific survival curves of elderly patients aged ≥70 years when comparing surgery alone vs. primary RT (A) and surgery plus adjuvant RT vs. primary RT (B). RT: radiotherapy; adj RT: adjuvant radiotherapy. (TIF)</p

Prognostic factors associated with disease-specific survival in matched cohorts A (surgery alone vs. primary RT) and B (surgery plus adjuvant RT vs. primary RT).

Prognostic factors associated with disease-specific survival in matched cohorts A (surgery alone vs. primary RT) and B (surgery plus adjuvant RT vs. primary RT).</p

Changes in the proportions of irradiation methods (beam radiation, brachytherapy and combination of beam radiation with brachytherapy) over time periods in the primary RT group.

RT: radiotherapy.</p

Definition of matched cohorts A and B.

RT: radiotherapy; adj RT: adjuvant RT. (TIF)</p

S3 Fig -

Receiver operator characteristic curves of disease-specific mortality in the matched cohorts A (A) and B (B) comparing age (red) and local treatment (blue). ROC: receiver operator characteristic; Tx: treatment; RT: radiotherapy; adj RT: adjuvant RT. (TIF)</p

Fig 4 -

Hazard rate function plots of disease-specific mortality in the matched cohorts A (A) and B (B): surgery alone (blue) vs. primary RT (red) and surgery plus adjuvant RT (blue) vs. primary RT (red), respectively. RT: radiotherapy; adj RT: adjuvant RT.</p

Institutional analyses of primary RT for early-stage oral tongue squamous cell carcinoma.

Institutional analyses of primary RT for early-stage oral tongue squamous cell carcinoma.</p

Fig 3 -

Overall and disease-specific survival curves when comparing surgery alone vs. primary RT (A, B) and surgery plus adjuvant RT vs. primary RT (C, D). RT: radiotherapy; adj RT: adjuvant radiotherapy.</p

Patient selection process flowchart.

RT: radiotherapy.</p

Clinicopathological characteristics of the initially identified study population with T1‒2N0 oral tongue squamous cell carcinoma (N = 8458).

(DOCX)</p