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1Department of Surgery, School of Medicine, Tulane University, New Orleans, LA, USA
2Department of Cardiovascular Perfusion, College of Health Professions, Upstate Medical University, New York, NY, USA
3Genetics Unit, Histology and Cell Biology Department, Faculty of Medicine, Suez Canal University, Ismailia, Egypt
4School of Medicine, Tulane University, New Orleans, LA, USA
5Ochsner Clinic Foundation, New Orleans, LA, USA
6Department of Anatomy, Faculty of Medicine, Jazan University, Jazan, Saudi Arabia
7Center for Health Research, Northern Border University, Arar, Saudi Arabia
Copyright © 2025 Korean Endocrine Society
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
CONFLICTS OF INTEREST
No potential conflict of interest relevant to this article was reported.
AUTHOR CONTRIBUTIONS
Conception or design: E.A.T., J.A.J., M.H.H., A.A.M.S., M.S.F., E.K. Acquisition, analysis, or interpretation of data: E.A.T., J.A.J., M.H.H. Drafting the work or revising: E.A.T., J.A.J., M.H.H., A.A.M.S., M.S.F., E.K. Final approval of the manuscript: E.A.T., J.A.J., M.H.H., A.A.M.S., M.S.F., E.K.
Characteristic | Total (n=101,164) | No ETE (n=98,835) | Laryngotracheal ETE (n=2,329) | P value |
---|---|---|---|---|
Demographics | ||||
Age | ||||
Median age, yr | 49 (38–60) | 49 (38–59) | 59 (46–71) | <0.001a |
≤55 | 64,675 (63.9) | 63,720 (64.5) | 955 (41.0) | <0.001a |
>55 | 36,489 (36.1) | 35,115 (35.5) | 1,374 (59.0) | |
Sex | <0.001a | |||
Female | 79,111 (78.2) | 77,607 (78.5) | 1,504 (64.6) | |
Male | 22,053 (21.8) | 21,228 (21.5) | 825 (35.4) | |
Race | <0.001a | |||
White | 83,344 (83.2) | 81,501 (83.3) | 1,843 (79.4) | |
Black | 6,516 (6.5) | 6,405 (6.5) | 111 (4.8) | |
Asian or Pacific Islander | 9,756 (9.7) | 9,411 (9.6) | 345 (14.9) | |
American Indian/Alaska native | 601 (0.6) | 578 (0.6) | 23 (1.0) | |
Hispanic/Latino | <0.001a | |||
No | 86,891 (85.9) | 85,115 (86.1) | 1,776 (76.3) | |
Yes | 14,273 (14.1) | 13,720 (13.9) | 553 (23.7) | |
Marital status | <0.001a | |||
Married/domestic partner | 63,730 (66.1) | 62,334 (66.2) | 1,396 (61.9) | |
Single | 19,612 (20.4) | 19,232 (20.4) | 380 (16.8) | |
Separated/divorced | 8,098 (8.4) | 7,903 (8.4) | 195 (8.6) | |
Widowed | 4,923 (5.1) | 4,637 (4.9) | 286 (12.7) | |
Residency | 0.510 | |||
Rural | 10,158 (10.1) | 9,915 (10) | 243 (10.5) | |
Urban | 90,909 (89.9) | 88,828 (90) | 2,081 (89.5) | |
Household income | 0.560 | |||
≥$75,000 | 67,547 (66.8) | 65,970 (66.7) | 1,577 (67.7) | |
<$75,000 | 33,607 (33.2) | 32,855 (33.2) | 752 (32.3) | |
Presentation | ||||
Histological type | 0.150 | |||
Papillary | 96,481 (95.4) | 94,245 (95.4) | 2,236 (96) | |
Follicular | 4,683 (4.6) | 4,590 (4.6) | 93 (4.0) | |
Prior cancer before TC | <0.001a | |||
Negative | 89,397 (88.4) | 87,427 (88.5) | 1,970 (84.6) | |
Positive | 11,767 (11.6) | 11,408 (11.5) | 359 (15.4) | |
T staging | <0.001a | |||
T1 | 60,973 (73.7) | 60,973 (75.2) | 0 | |
T2 | 15,227 (18.4) | 15,227 (18.8) | 0 | |
T3 | 4,828 (5.8) | 4,828 (6.0) | 0 | |
T4a | 1,425 (1.7) | 53 (0.1) | 1,372 (85.4) | |
T4b | 235 (0.3) | 0 | 235 (14.6) | |
N staging | <0.001a | |||
N0 | 82,553 (83.9) | 81,719 (84.9) | 834 (38.2) | |
N1 | 15,895 (16.1) | 14,547 (15.1) | 1,348 (61.8) | |
M staging | <0.001 | |||
M0 | 100,506 (99.3) | 98,393 (99.6) | 2,113 (90.7) | |
M1 | 658 (0.7) | 442 (0.4) | 216 (9.3) |
Values are expressed as median (interquartile range) or number (%). Two-sided chi-square and Fisher exact tests were used. A tumor of any size that invades the subcutaneous soft tissues, larynx, trachea, esophagus, or recurrent laryngeal nerve is staged as T4a, while a tumor that invades prevertebral fascia, mediastinal vessels, or carotid artery is staged as T4b, according to the International Union Against Cancer.
ETE, extrathyroidal extension; TC, thyroid cancer.
a P<0.05.
Characteristic | Total (n=101,164) | No ETE (n=98,835) | Laryngotracheal ETE (n=2,329) | P value |
---|---|---|---|---|
Management | ||||
Cancer-directed surgery | <0.001a | |||
Overall | 99,846 (98.7) | 97,632 (98.8) | 2,214 (95.1) | |
Lobectomy and/or isthmectomy | 17,011 (16.8) | 16,860 (17.1) | 151 (6.5) | |
Subtotal thyroidectomy | 5,314 (5.3) | 5,177 (5.2) | 137 (5.9) | |
Total thyroidectomy | 76,672 (75.8) | 74,782 (75.7) | 1,890 (81.2) | |
Surgery, NOS | 813 (0.8) | 36 (1.5) | 849 (0.8) | |
Surgery at other sites | <0.001a | |||
Regional sites or lymph nodes | 366 (3.1) | 310 (2.7) | 56 (10.6) | |
Distant lymph nodes | 666 (5.6) | 624 (5.5) | 42 (8.0) | |
Distant sites | 376 (3.2) | 294 (2.6) | 82 (15.5) | |
Adjuvant therapy | <0.001a | |||
Radioactive ablation | 41,244 (40.8) | 39,887 (40.4) | 1,357 (58.3) | |
Radiation therapy | 44,470 (44.0) | 42,720 (43.2) | 1,750 (75.1) | |
Systemic therapy | 33,833 (47.3) | 33,143 (47.2) | 690 (54.6) | |
Outcomes | ||||
Recurrence | ||||
Positive | 408 (0.4) | 393 (0.4) | 15 (0.6) | 0.070 |
Second primary cancers | ||||
Positive | 20,966 (20.7) | 20,345 (20.6) | 621 (26.7) | <0.001a |
Survival status | <0.001a | |||
Alive | 90,370 (89.3) | 89,066 (90.1) | 1,304 (56.0) | |
Dead | 10,794 (10.7) | 9,769 (9.9) | 1,025 (44.0) | |
Cause of death | <0.001a | |||
Alive | 90,370 (89.3) | 89,066 (90.1) | 1,304 (56.0) | |
Dead, other cancer | 9,078 (9.0) | 8,655 (8.8) | 423 (18.2) | |
Dead, TC | 1,716 (1.7) | 1,114 (1.1) | 602 (25.8) |
Variable |
Overall mortality |
Thyroid cancer-specific mortality |
||
---|---|---|---|---|
HR (95% CI) | P value | HR (95% CI) | P value | |
Age ≥55 years vs. <55 years | 1.18 (1.05–1.33) | 0.005a | 5.92 (4.69–7.48) | <0.001a |
Sex: male vs. female | 1.05 (0.91–1.18) | 0.450 | 1.29 (1.08–1.54) | 0.005a |
Race: Black vs. White | 1.16 (0.88–1.53) | 0.310 | 0.97 (0.63–1.52) | 0.880 |
Race: Asian or Pacific Islander vs. White | 1.10 (0.94–1.29) | 0.260 | 0.62 (0.48–0.84) | 0.001a |
Race: American Indian/Alaska Native vs. White | 1.13 (0.56–2.30) | 0.740 | 2.04 (0.91–4.64) | 0.090 |
Ethnicity: Hispanic/Latino vs. none | 1.32 (1.16–1.52) | <0.001a | 0.83 (0.67–1.04) | 0.090 |
Income: ≥$75,000 vs. <$75,000 | 1.09 (0.97–1.24) | 0.170 | 1.18 (0.98–1.47) | 0.100 |
Residence: urban vs. rural | 0.99 (0.82–1.20) | 0.910 | 0.86 (0.66–1.23) | 0.290 |
Histological type: FTC vs. PTC | 0.64 (0.42–0.95) | 0.023a | 1.26 (0.82–2.2) | 0.270 |
T staging: T4b vs. T4a | 1.38 (1.14–1.67) | 0.001a | 1.62 (1.28–2.05) | <0.001a |
N staging: N1 vs. N0 | 1.03 (0.90–1.16) | 0.680 | 1.44 (1.22–1.78) | <0.001a |
M staging: M1 vs. M0 | 1.75 (1.30–2.29) | <0.001a | 2.52 (2.04–3.21) | <0.001a |
Cancer-directed surgery vs. none | 0.78 (0.42–1.43) | 0.400 | 0.34 (0.26–0.52) | <0.001a |
Radioactive iodine vs. none | 1.13 (0.94–1.34) | 0.200 | 0.50 (0.41–0.65) | <0.001a |
External beam radiation vs. none | 1.05 (0.85–1.27) | 0.710 | 0.99 (0.80–1.29) | 0.950 |
Systemic therapy vs. none | 0.77 (0.65–1.02) | 0.060 | 0.83 (0.68–1.03) | 0.090 |
Multivariate Cox proportional hazards regression analysis was conducted, adjusting for potential demographic and clinical confounders, which included age, sex, race, ethnicity, income, residence, histological type, tumor staging, nodal staging, metastasis staging, and treatment modalities. HR and 95% CI were reported using surgery only as a reference.
HR, hazard ratio; CI, confidence interval; FTC, follicular thyroid cancer; PTC, papillary thyroid cancer.
a P<0.05.
Treatment received |
Overall mortality, mo |
Thyroid cancer-specific mortality, mo |
||||
---|---|---|---|---|---|---|
Mean | SD | P value | Mean | SD | P value | |
Cancer-directed surgery only | 133.2 | 5.41 | Ref | 157.1 | 6.57 | Ref |
Surgery+RAI | 167.7 | 2.61 | <0.001a | 189.8 | 2.69 | <0.001a |
Surgery+EBR | 109.2 | 5.85 | 0.150 | 124.0 | 6.88 | 0.033a |
Surgery+systemic therapy | 86.9 | 8.64 | 0.990 | 99.3 | 10.5 | 0.990 |
Surgery+RAI+systemic therapy | 156.7 | 5.63 | 0.004a | 184.5 | 5.78 | 0.001a |
Surgery+EBR+systemic therapy | 84.9 | 10.9 | 0.008a | 88.8 | 12.6 | 0.001a |
No treatment | 40.1 | 14.2 | <0.001a | 45.6 | 17.7 | <0.001a |
Pairwise comparison | Subject per arm |
Overall mortality |
Thyroid cancer-specific mortality |
||||
---|---|---|---|---|---|---|---|
HR | 95% CI | P value | HR | 95% CI | P value | ||
Surgery+RAI vs. surgery only | 345 | 0.70 | 0.56–0.86 | <0.001a | 0.67 | 0.50–0.89 | 0.007a |
Surgery+EBR vs. surgery only | 253 | 1.11 | 0.89–1.39 | 0.360 | 1.21 | 0.91–1.61 | 0.200 |
Surgery+systemic therapy vs. surgery only | 48 | 0.81 | 0.47–1.41 | 0.460 | 0.60 | 0.29–1.26 | 0.180 |
Surgery+RAI+systemic therapy vs. surgery only | 346 | 0.69 | 0.53–0.90 | 0.006a | 0.62 | 0.43–0.88 | 0.009a |
Surgery+EBR+systemic therapy vs. surgery only | 64 | 1.58 | 1.01–2.47 | 0.046a | 2.08 | 1.17–3.71 | 0.013a |
No management vs. surgery only | 25 | 0.97 | 0.53–1.76 | 0.910 | 1.01 | 0.48–2.12 | 0.980 |
Matching was performed using 1:1 nearest neighbor propensity score matching without replacement. Propensity scores were calculated using logistic regression based on the following covariates: age, sex, race, ethnicity, income, residence, tumor size, nodal stage, metastases, and histology. Matches were made using a caliper width of 0.2 of the standard deviation of the logit of the propensity score. The balance between matched pairs was assessed using standardized mean differences, with values <0.1 considered to indicate good balance. Univariate Cox regression models were conducted for each comparison.
HR and 95% CI were reported using surgery only as a reference.
HR, hazard ratio; CI, confidence interval; RAI, radioactive iodine ablation; EBR, external beam radiation.
a P<0.05.
Characteristic | Total (n=101,164) | No ETE (n=98,835) | Laryngotracheal ETE (n=2,329) | P value |
---|---|---|---|---|
Demographics | ||||
Age | ||||
Median age, yr | 49 (38–60) | 49 (38–59) | 59 (46–71) | <0.001 |
≤55 | 64,675 (63.9) | 63,720 (64.5) | 955 (41.0) | <0.001 |
>55 | 36,489 (36.1) | 35,115 (35.5) | 1,374 (59.0) | |
Sex | <0.001 |
|||
Female | 79,111 (78.2) | 77,607 (78.5) | 1,504 (64.6) | |
Male | 22,053 (21.8) | 21,228 (21.5) | 825 (35.4) | |
Race | <0.001 |
|||
White | 83,344 (83.2) | 81,501 (83.3) | 1,843 (79.4) | |
Black | 6,516 (6.5) | 6,405 (6.5) | 111 (4.8) | |
Asian or Pacific Islander | 9,756 (9.7) | 9,411 (9.6) | 345 (14.9) | |
American Indian/Alaska native | 601 (0.6) | 578 (0.6) | 23 (1.0) | |
Hispanic/Latino | <0.001 |
|||
No | 86,891 (85.9) | 85,115 (86.1) | 1,776 (76.3) | |
Yes | 14,273 (14.1) | 13,720 (13.9) | 553 (23.7) | |
Marital status | <0.001 |
|||
Married/domestic partner | 63,730 (66.1) | 62,334 (66.2) | 1,396 (61.9) | |
Single | 19,612 (20.4) | 19,232 (20.4) | 380 (16.8) | |
Separated/divorced | 8,098 (8.4) | 7,903 (8.4) | 195 (8.6) | |
Widowed | 4,923 (5.1) | 4,637 (4.9) | 286 (12.7) | |
Residency | 0.510 | |||
Rural | 10,158 (10.1) | 9,915 (10) | 243 (10.5) | |
Urban | 90,909 (89.9) | 88,828 (90) | 2,081 (89.5) | |
Household income | 0.560 | |||
≥$75,000 | 67,547 (66.8) | 65,970 (66.7) | 1,577 (67.7) | |
<$75,000 | 33,607 (33.2) | 32,855 (33.2) | 752 (32.3) | |
Presentation | ||||
Histological type | 0.150 | |||
Papillary | 96,481 (95.4) | 94,245 (95.4) | 2,236 (96) | |
Follicular | 4,683 (4.6) | 4,590 (4.6) | 93 (4.0) | |
Prior cancer before TC | <0.001 |
|||
Negative | 89,397 (88.4) | 87,427 (88.5) | 1,970 (84.6) | |
Positive | 11,767 (11.6) | 11,408 (11.5) | 359 (15.4) | |
T staging | <0.001 |
|||
T1 | 60,973 (73.7) | 60,973 (75.2) | 0 | |
T2 | 15,227 (18.4) | 15,227 (18.8) | 0 | |
T3 | 4,828 (5.8) | 4,828 (6.0) | 0 | |
T4a | 1,425 (1.7) | 53 (0.1) | 1,372 (85.4) | |
T4b | 235 (0.3) | 0 | 235 (14.6) | |
N staging | <0.001 |
|||
N0 | 82,553 (83.9) | 81,719 (84.9) | 834 (38.2) | |
N1 | 15,895 (16.1) | 14,547 (15.1) | 1,348 (61.8) | |
M staging | <0.001 | |||
M0 | 100,506 (99.3) | 98,393 (99.6) | 2,113 (90.7) | |
M1 | 658 (0.7) | 442 (0.4) | 216 (9.3) |
Characteristic | Total (n=101,164) | No ETE (n=98,835) | Laryngotracheal ETE (n=2,329) | P value |
---|---|---|---|---|
Management | ||||
Cancer-directed surgery | <0.001 |
|||
Overall | 99,846 (98.7) | 97,632 (98.8) | 2,214 (95.1) | |
Lobectomy and/or isthmectomy | 17,011 (16.8) | 16,860 (17.1) | 151 (6.5) | |
Subtotal thyroidectomy | 5,314 (5.3) | 5,177 (5.2) | 137 (5.9) | |
Total thyroidectomy | 76,672 (75.8) | 74,782 (75.7) | 1,890 (81.2) | |
Surgery, NOS | 813 (0.8) | 36 (1.5) | 849 (0.8) | |
Surgery at other sites | <0.001 |
|||
Regional sites or lymph nodes | 366 (3.1) | 310 (2.7) | 56 (10.6) | |
Distant lymph nodes | 666 (5.6) | 624 (5.5) | 42 (8.0) | |
Distant sites | 376 (3.2) | 294 (2.6) | 82 (15.5) | |
Adjuvant therapy | <0.001 |
|||
Radioactive ablation | 41,244 (40.8) | 39,887 (40.4) | 1,357 (58.3) | |
Radiation therapy | 44,470 (44.0) | 42,720 (43.2) | 1,750 (75.1) | |
Systemic therapy | 33,833 (47.3) | 33,143 (47.2) | 690 (54.6) | |
Outcomes | ||||
Recurrence | ||||
Positive | 408 (0.4) | 393 (0.4) | 15 (0.6) | 0.070 |
Second primary cancers | ||||
Positive | 20,966 (20.7) | 20,345 (20.6) | 621 (26.7) | <0.001 |
Survival status | <0.001 |
|||
Alive | 90,370 (89.3) | 89,066 (90.1) | 1,304 (56.0) | |
Dead | 10,794 (10.7) | 9,769 (9.9) | 1,025 (44.0) | |
Cause of death | <0.001 |
|||
Alive | 90,370 (89.3) | 89,066 (90.1) | 1,304 (56.0) | |
Dead, other cancer | 9,078 (9.0) | 8,655 (8.8) | 423 (18.2) | |
Dead, TC | 1,716 (1.7) | 1,114 (1.1) | 602 (25.8) |
Variable | Overall mortality |
Thyroid cancer-specific mortality |
||
---|---|---|---|---|
HR (95% CI) | P value | HR (95% CI) | P value | |
Age ≥55 years vs. <55 years | 1.18 (1.05–1.33) | 0.005 |
5.92 (4.69–7.48) | <0.001 |
Sex: male vs. female | 1.05 (0.91–1.18) | 0.450 | 1.29 (1.08–1.54) | 0.005 |
Race: Black vs. White | 1.16 (0.88–1.53) | 0.310 | 0.97 (0.63–1.52) | 0.880 |
Race: Asian or Pacific Islander vs. White | 1.10 (0.94–1.29) | 0.260 | 0.62 (0.48–0.84) | 0.001 |
Race: American Indian/Alaska Native vs. White | 1.13 (0.56–2.30) | 0.740 | 2.04 (0.91–4.64) | 0.090 |
Ethnicity: Hispanic/Latino vs. none | 1.32 (1.16–1.52) | <0.001 |
0.83 (0.67–1.04) | 0.090 |
Income: ≥$75,000 vs. <$75,000 | 1.09 (0.97–1.24) | 0.170 | 1.18 (0.98–1.47) | 0.100 |
Residence: urban vs. rural | 0.99 (0.82–1.20) | 0.910 | 0.86 (0.66–1.23) | 0.290 |
Histological type: FTC vs. PTC | 0.64 (0.42–0.95) | 0.023 |
1.26 (0.82–2.2) | 0.270 |
T staging: T4b vs. T4a | 1.38 (1.14–1.67) | 0.001 |
1.62 (1.28–2.05) | <0.001 |
N staging: N1 vs. N0 | 1.03 (0.90–1.16) | 0.680 | 1.44 (1.22–1.78) | <0.001 |
M staging: M1 vs. M0 | 1.75 (1.30–2.29) | <0.001 |
2.52 (2.04–3.21) | <0.001 |
Cancer-directed surgery vs. none | 0.78 (0.42–1.43) | 0.400 | 0.34 (0.26–0.52) | <0.001 |
Radioactive iodine vs. none | 1.13 (0.94–1.34) | 0.200 | 0.50 (0.41–0.65) | <0.001 |
External beam radiation vs. none | 1.05 (0.85–1.27) | 0.710 | 0.99 (0.80–1.29) | 0.950 |
Systemic therapy vs. none | 0.77 (0.65–1.02) | 0.060 | 0.83 (0.68–1.03) | 0.090 |
Treatment received | Overall mortality, mo |
Thyroid cancer-specific mortality, mo |
||||
---|---|---|---|---|---|---|
Mean | SD | P value | Mean | SD | P value | |
Cancer-directed surgery only | 133.2 | 5.41 | Ref | 157.1 | 6.57 | Ref |
Surgery+RAI | 167.7 | 2.61 | <0.001 |
189.8 | 2.69 | <0.001 |
Surgery+EBR | 109.2 | 5.85 | 0.150 | 124.0 | 6.88 | 0.033 |
Surgery+systemic therapy | 86.9 | 8.64 | 0.990 | 99.3 | 10.5 | 0.990 |
Surgery+RAI+systemic therapy | 156.7 | 5.63 | 0.004 |
184.5 | 5.78 | 0.001 |
Surgery+EBR+systemic therapy | 84.9 | 10.9 | 0.008 |
88.8 | 12.6 | 0.001 |
No treatment | 40.1 | 14.2 | <0.001 |
45.6 | 17.7 | <0.001 |
Pairwise comparison | Subject per arm | Overall mortality |
Thyroid cancer-specific mortality |
||||
---|---|---|---|---|---|---|---|
HR | 95% CI | P value | HR | 95% CI | P value | ||
Surgery+RAI vs. surgery only | 345 | 0.70 | 0.56–0.86 | <0.001 |
0.67 | 0.50–0.89 | 0.007 |
Surgery+EBR vs. surgery only | 253 | 1.11 | 0.89–1.39 | 0.360 | 1.21 | 0.91–1.61 | 0.200 |
Surgery+systemic therapy vs. surgery only | 48 | 0.81 | 0.47–1.41 | 0.460 | 0.60 | 0.29–1.26 | 0.180 |
Surgery+RAI+systemic therapy vs. surgery only | 346 | 0.69 | 0.53–0.90 | 0.006 |
0.62 | 0.43–0.88 | 0.009 |
Surgery+EBR+systemic therapy vs. surgery only | 64 | 1.58 | 1.01–2.47 | 0.046 |
2.08 | 1.17–3.71 | 0.013 |
No management vs. surgery only | 25 | 0.97 | 0.53–1.76 | 0.910 | 1.01 | 0.48–2.12 | 0.980 |
Values are expressed as median (interquartile range) or number (%). Two-sided chi-square and Fisher exact tests were used. A tumor of any size that invades the subcutaneous soft tissues, larynx, trachea, esophagus, or recurrent laryngeal nerve is staged as T4a, while a tumor that invades prevertebral fascia, mediastinal vessels, or carotid artery is staged as T4b, according to the International Union Against Cancer. ETE, extrathyroidal extension; TC, thyroid cancer.
Values are expressed as number (%). Two-sided chi-square and Mann-Whitney ETE, extrathyroidal extension; NOS, not otherwise specified; TC, thyroid cancer.
Multivariate Cox proportional hazards regression analysis was conducted, adjusting for potential demographic and clinical confounders, which included age, sex, race, ethnicity, income, residence, histological type, tumor staging, nodal staging, metastasis staging, and treatment modalities. HR and 95% CI were reported using surgery only as a reference. HR, hazard ratio; CI, confidence interval; FTC, follicular thyroid cancer; PTC, papillary thyroid cancer.
The log-rank test was used with the Bonferroni adjustment method. SD, standard deviation; RAI, radioactive iodine ablation; EBR, external beam radiation.
Matching was performed using 1:1 nearest neighbor propensity score matching without replacement. Propensity scores were calculated using logistic regression based on the following covariates: age, sex, race, ethnicity, income, residence, tumor size, nodal stage, metastases, and histology. Matches were made using a caliper width of 0.2 of the standard deviation of the logit of the propensity score. The balance between matched pairs was assessed using standardized mean differences, with values <0.1 considered to indicate good balance. Univariate Cox regression models were conducted for each comparison. HR and 95% CI were reported using surgery only as a reference. HR, hazard ratio; CI, confidence interval; RAI, radioactive iodine ablation; EBR, external beam radiation.