Baseline Clinical Characteristics
| Characteristic | Data |
| Age (y) | |
| Median | 64 |
| Range | 22–89 |
| Sex (n) | |
| Male | 227 (74%) |
| Female | 80 (26%) |
| Tumor site (n) | |
| Oral cavity | 147 (48%) |
| Pharynx | 103 (34%) |
| Larynx | 57 (18%) |
| Verified distant metastasis* (n) | |
| M0 | 289 (94%) |
| M1 | 18 (6%) |
| p16 status (n) | |
| Negative | 242 (79%) |
| Positive | 65 (21%) |
| Follow-up (d) | |
| Median | 461 |
| Range | 21–1,092 |
↵* 84% of cases were confirmed with follow-up imaging (within 6 mo), 8% with histology, and 8% with cytology. When only imaging was available as a validator, we applied RECIST for measurable lesions and progression. Only lesions fulfilling RECIST for progression were characterized as metastatic disease.