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Table 1 Characteristics of thyroid cancer cases and non-cases at baseline among South Korean medical radiation workers, 1996–2015

From: Thyroid cancer risks among medical radiation workers in South Korea, 1996–2015

  Thyroid cancer cases (n = 827) Thyroid non-cases (n = 93,095)
Numbers (%) Numbers (%)
Person-years at risk 6772 1,094,676
Sex
 Male 309 (37.4) 53,276 (57.2)
 Female 518 (62.6) 39,819 (42.8)
Age at baseline, years
  < 25 167 (20.2) 20,785 (22.3)
 25–29 227 (27.5) 26,594 (28.6)
 30–39 295 (35.7) 29,776 (32.0)
  ≥ 40 138 (16.7) 15,940 (17.1)
Calendar year of birth
  < 1960 94 (11.4) 10,403 (11.2)
 1960–1969 259 (31.3) 24,085 (25.9)
 1970–1979 321 (38.8) 32,576 (35.0)
  ≥ 1980 153 (18.5) 26,031 (28.0)
Calendar year of entry
 1996–1999 280 (33.9) 23,066 (24.8)
 2000–2004 239 (28.9) 24,689 (26.5)
 2005–2011 308 (37.2) 45,340 (48.7)
Type of medical facility
 Hospital 291 (35.2) 31,375 (33.7)
 Clinic 229 (27.7) 25,906 (27.8)
 Others 307 (37.1) 35,814 (38.5)
Duration of employment, years
  < 1 90 (10.9) 13,349 (14.3)
 1–4 294 (35.6) 36,449 (39.2)
 5–9 210 (25.4) 22,517 (24.2)
  ≥ 10 233 (28.2) 20,780 (22.3)
Cumulative thyroid dose (mGy),
 Mean ± SD 9.9 ± 32.3 10.4 ± 41.6
 Median (range) 1.5 (0.007, 579.2) 1.4 (0.007, 9861.2)
  < 0.5 245 (29.6) 29,970 (32.2)
 0.5–1.0 100 (12.1) 11,515 (12.4)
 1.0–2.5 138 (16.7) 14,393 (15.5)
 2.5–5.0 89 (10.8) 8710 (9.4)
 5.0–10.0 66 (8.0) 8296 (8.9)
 10.0–20.0 85 (10.3) 7265 (7.8)
  ≥ 20.0 104 (12.6) 12,946 (13.9)
Age at diagnosis, years
  < 30 112 (13.5)
 30–39 309 (37.4)
 40–49 292 (35.3)
  ≥ 50 114 (13.8)
Histological type
 Papillary 798 (96.5)
 Follicular 9 (1.1)
 Medullary 5 (0.6)
 Others 15 (1.8)
SEER summary stage
 Localized 311 (37.6)
 Regional 408 (49.3)
 Distant 5 (0.7)
 Unknown/missing 103 (12.4)
  1. SD standard deviation, SEER Surveillance, Epidemiology and End Results