Table 1.
Characteristics of study population. Values are numbers (percentages) unless stated otherwise
| Variables | Total | Year | P value* | ||
|---|---|---|---|---|---|
| 1999 | 2005 | 2008 | |||
| Overall | 5796 | 891 | 2355 | 2550 | |
| Mean (SD) age (years) | 46.9 (12.4) | 46.0 (14.3) | 47.3 (12.5) | 46.8 (11.6) | 0.03 |
| Mean (SD) tumour size (mm) | 13.3 (11.7) | 21.5 (15.9) | 13.6 (11.1) | 10.5 (9.0) | <0.01 |
| Sex: | 0.01 | ||||
| Men | 898 (15.5) | 136 (15.3) | 328 (13.9) | 434 (17.0) | |
| Women | 4898 (84.5) | 755 (84.7) | 2027 (86.1) | 2116 (83.0) | |
| Methods of detection†: | <0.01 | ||||
| Screening | 2655 (45.8) | 134 (15.0) | 1090 (46.3) | 1431 (56.1) | |
| Clinical | 1784 (30.8) | 447 (50.2) | 773 (32.8) | 564 (22.1) | |
| Unspecified | 1357 (23.4) | 310 (34.8) | 492 (20.9) | 555 (21.8) | |
| Histological type‡: | <0.01 | ||||
| Follicular carcinoma | 173 (3.0) | 62 (7.0) | 66 (2.8) | 45 (1.8) | |
| Papillary carcinoma | 5500 (94.9) | 779 (87.4) | 2243 (95.2) | 2478 (97.2) | |
| Medullary carcinoma | 43 (0.7) | 13 (1.4) | 19 (0.8) | 11 (0.4) | |
| Anaplastic carcinoma | 26 (0.5) | 15 (1.7) | 6 (0.3) | 5 (0.2) | |
| Other | 54 (0.9) | 22 (2.5) | 21 (0.9) | 11 (0.4) | |
| Regional lymph node involvement: | <0.01 | ||||
| No | 2466 (42.6) | 268 (30.1) | 1012 (43.0) | 1186 (46.5) | |
| Yes | 2047 (35.3) | 319 (35.8) | 799 (33.9) | 929 (36.4) | |
| Unknown | 1283 (22.1) | 304 (34.1) | 544 (23.1) | 435 (17.1) | |
| Distant metastasis: | <0.01 | ||||
| No | 5380 (92.8) | 774 (86.9) | 2196 (93.3) | 2410 (94.5) | |
| Yes | 34 (0.6) | 15 (1.7) | 14 (0.6) | 5 (0.2) | |
| Unknown | 382 (6.6) | 102 (11.4) | 145 (6.1) | 135 (5.3) | |
| Extrathyroidal extension: | <0.01 | ||||
| No | 2783 (48.0) | 397 (44.5) | 1194 (50.7) | 1192 (46.7) | |
| Yes | 2593 (44.7) | 357 (40.1) | 993 (42.2) | 1243 (48.8) | |
| Unknown | 420 (7.3) | 137 (15.4) | 168 (7.1) | 115 (4.5) | |
| Focality: | <0.01 | ||||
| Unifocal | 3810 (66.7) | 554 (62.2) | 1553 (65.9) | 1703 (66.8) | |
| Multifocal | 1697 (29.3) | 234 (26.3) | 689 (29.3) | 774 (30.3) | |
| Unknown | 289 (5.0) | 103 (11.5) | 113 (4.8) | 73 (2.9) | |
| American Joint Committee on Cancer stage: | <0.01 | ||||
| I | 3038 (52.4) | 428 (48.0) | 1249 (53.0) | 1361 (53.3) | |
| II | 49 (0.9) | 14 (1.6) | 23 (1.0) | 12 (0.5) | |
| III | 1036 (17.9) | 97 (10.9) | 373 (15.8) | 566 (22.2) | |
| IV | 426 (7.3) | 101 (11.3) | 178 (7.6) | 147 (5.8) | |
| Unknown | 1247 (21.5) | 251 (28.2) | 532 (22.6) | 464 (18.2) | |
| SEER summary stage: | <0.01 | ||||
| Localised | 2125 (36.6) | 302 (33.9) | 919 (39.0) | 904 (35.5) | |
| Regional | 3176 (54.8) | 425 (47.7) | 1243 (52.8) | 1508 (59.1) | |
| Distant | 126 (2.2) | 48 (5.4) | 45 (1.9) | 33 (1.3) | |
| Unknown | 369 (6.4) | 116 (13.0) | 148 (6.3) | 105 (4.1) | |
SEER=Surveillance, Epidemiology, and End Results.
*Calculated by one way analysis of variance for continuous variables and χ2test for categorical variables.
†Classified as screen detected (as recorded in medical records), clinically detected (through investigation of symptoms associated with thyroid disease, including thyroid cancer), and unspecified (or unknown).
‡Classified based on International Agency for Research on Cancer (international classification of diseases for oncology, third edition). Extrathyroidal extension was determined on the basis of the American Joint Committee on Cancer (cancer staging manual, sixth edition).