Table 1 Characteristics of population-based cohort of 33,787 patients diagnosed the first primary cancer as oral and pharyngeal (including oral cavity, oropharyngeal, or hypopharyngeal) carcinoma, 1979-2003.
| Â | Â | Oral cavity | Oropharynx | Hypopharynx |
ICD | Â | 140, 141, 143, 144, 145 | 146, 149 | 148 |
No. with first primary cancer | All | 26,166 | 3,403 | 4,218 |
| Â | M | 23,320 | 2,788 | 4,068 |
| Â | F | 2,846 | 615 | 150 |
No. who developed a second primary cancer (%)* | All | 1,800 (6.88) | 232 (6.82) | 347 (8.23) |
| Â | M | 1,654 (7.09) | 197 (7.07) | 335(8.24) |
| Â | F | 146 (5.13) | 35 (5.69) | 12 (8.00) |
No. who developed the second esophageal cancer (%)* | All | 99 (0.38) | 30 (0.88) | 71 (1.68) |
| Â | M | 99 (0.42) | 29 (1.04) | 69 (1.70) |
| Â | F | 0 (0) | 1 (0.16) | 2 (1.33) |
Average (± sd) age at diagnosis of first cancer (yrs) |  | 52.70 ± 12.54 | 54.75 ± 13.17 | 58.48 ± 11.75 |
Average (± sd) age at diagnosis of a second cancer (yrs) |  | 56.70 ± 11.87 | 57.70 ± 12.11 | 60.12 ± 11.38 |
Average (± sd) age at diagnosis of the second esophageal cancer (yrs.) |  | 57.59 ± 10.46 | 51.77 ± 10.52 | 57.55 ± 10.15 |
Average (± sd) interval between the first primary and second cancers (yrs.) |  | 3.25 ± 3.51 | 2. 64 ± 3.47 | 2.47 ± 3.32 |
Average (± sd) interval between the first primary and the second esophageal cancer (yrs.) |  | 3.10 ± 2.64 | 1.24 ± 1.16 | 2.23 ± 2.76 |
Average follow-up (yrs) |  | 3.60 ± 4.15 | 3.39 ± 4.32 | 2.65 ± 3.80 |