The role of radioactive iodine therapy in papillary thyroid cancer: an observational study based on SEER

Figures & data

Table 1 Patient characteristics within subgroups

Variables	No RAI therapy N=18,222 (%)	RAI therapy N=23,065 (%)	P-value*
Median follow-up (months)	42.2	50.8
Age at diagnosis, years			<0.001
<45	7,078 (38.8)	10,534 (45.7)
≥45	11,144 (61.2)	12,531 (54.3)
Sex			<0.001
Male	3,596 (19.7)	5,695 (24.7)
Female	14,626 (80.3)	17,370 (75.3)
Race			<0.001
White	14,995 (82.3)	18,972 (82.3)
Black	1,116 (6.1)	903 (3.9)
Asian	1,689 (9.3)	2,655 (11.5)
Other	275 (1.5)	445 (1.9)
Unknown	147 (0.8)	90 (0.4)
Region			<0.001
East	7,255 (39.8)	7,532 (32.7)
Pacific Coast	8,293 (45.5)	11,839 (51.3)
Southwest	1,169 (6.4)	1,653 (7.2)
Northern Plains	1,500 (8.2)	2,021 (8.8)
Alaska	5 (0.0)	20 (0.1)
Surgery			<0.001
Subtotal or near total thyroidectomy	991 (5.4)	642 (2.8)
Total thyroidectomy	17,231 (94.6)	22,423 (97.2)
Tumor size (cm)			<0.001
≤2	14,817 (81.3)	14,629 (63.4)
>2	3,405 (18.7)	8,436 (36.6)
Tumor extension			<0.001
Intrathyroidal	16,230 (89.1)	16,708 (72.4)
Minimal extrathyroidal	851 (4.7)	2,651 (11.5)
Gross extrathyroidal	1,141 (6.3)	3,706 (16.1)
Lymph node metastases			<0.001
Negative	15,634 (85.8)	14,290 (62.0)
Positive	2,588 (14.2)	8,775 (38.0)
Distant metastases			<0.001
None	18,154 (99.6)	22,831 (99.0)
Yes	68 (0.4)	234 (1.0)
Status			<0.001
Alive	17,520 (96.1)	22,344 (96.9)
Dead	702 (3.9)	721 (3.1)
Thyroid cancer	94 (0.5)	167 (0.7)
Other	608 (3.3)	554 (2.4)

Note:

* P-values were calculated by Pearson chi-squared or Fisher’s exact testing.

Abbreviation: RAI, radioactive iodine.

Table 2 Cox proportional hazards regression model analysis of overall survival (OS) and disease-specific survival (DSS)

Variables	OS		DSS
	aHR (95% CI)	P-value*	aHR (95% CI)	P-value*
Age at diagnosis, years
<45	Reference		Reference
≥45	6.730 (5.649, 8.018)	<0.001	20.332 (10.774, 38.368)	<0.001
Sex
Male	Reference		Reference
Female	0.567 (0.508, 0.633)	<0.001	0.656 (0.509, 0.844)	0.001
Race
White	Reference		Reference
Black	1.237 (0.988, 1.549)	0.064	1.065 (0.560, 2.026)	0.848
Asian	0.734 (0.599, 0.899)	0.003	0.844 (0.575, 1.238)	0.385
Other	1.231 (0.832, 1.821)	0.298	1.349 (0.628, 2.901)	0.443
Region
East	Reference		Reference
Pacific Coast	0.930 (0.826, 1.047)	0.229	1.087 (0.818, 1.445)	0.566
Southwest	0.909 (0.722, 1.143)	0.413	0.546 (0.279, 1.069)	0.077
Northern Plains	1.139 (0.948, 1.368)	0.165	1.113 (0.697, 1.776)	0.654
Alaska	1.453 (0.342, 6.173)	0.613	0.000 (0.000, 6.575E+266)	0.973
Surgery
Subtotal or near total thyroidectomy	Reference		Reference
Total thyroidectomy	0.815 (0.656, 1.012)	0.064	0.590 (0.354, 0.986)	0.044
RAI therapy
None	Reference		Reference
Yes	0.586 (0.525, 0.655)	<0.001	0.600 (0.461, 0.780)	<0.001
Tumor size (cm)
≤2	Reference		Reference
>2	1.493 (1.331, 1.674)	<0.001	3.704 (2.758, 4.975)	<0.001
Extension
Intrathyroidal	Reference		Reference
Minimal extrathyroidal	1.201 (0.985, 1.463)	0.070	2.325 (1.517, 3.562)	<0.001
Gross extrathyroidal	1.995 (1.740, 2.288)	<0.001	5.047 (3.682, 6.916)	<0.001
Lymph node metastases
Negative	Reference		Reference
Positive	1.290 (1.137, 1.463)	<0.001	2.103 (1.589, 2.784)	<0.001
Distant metastases
None	Reference		Reference
Yes	5.398 (4.291, 6.790)	<0.001	10.257 (7.422, 14.176)	<0.001

Note:

* P-values calculated by multivariate Cox analysis.

Abbreviations: aHR, adjusted hazard ratio (adjusted for age at diagnosis, sex, race, region, tumor size, extension, lymph nodes metastases, distant metastases, radiotherapy and surgery); RAI, radioactive iodine.

Table 3 Cox proportional hazards regression model analysis of overall survival (OS) and disease-specific survival (DSS) of patients stratified by patients’ features

	OS		DSS
	aHR (95% CI)	P-value*	aHR (95% CI)	P-value*
Tumor size <2 cm
No RAI therapy	Reference		Reference
RAI therapy	0.651 (0.563, 0.752)	<0.001	0.785 (0.471, 1.823)	0.352
Tumor size ≥2 cm
No RAI therapy	Reference		Reference
RAI therapy	0.509 (0.430, 0.603)	<0.001	0.509 (0.430, 0.603)	<0.001
Age <45 years
No RAI therapy	Reference		Reference
RAI therapy	0.591 (0.418, 0.836)	0.003	1.846 (0.227, 14.978)	0.566
Age ≥45 years
No RAI therapy	Reference		Reference
RAI therapy	0.584 (0.520, 0.657)	<0.001	0.582 (0.445, 0.760)	<0.001
Intrathyroidal extension
No RAI therapy	Reference		Reference
RAI therapy	0.638 (0.557, 0.730)	<0.001	1.042 (0.648, 1.677)	0.856
MEE
No RAI therapy	Reference		Reference
RAI therapy	0.742 (0.493, 1.115)	<0.001	1.356 (0.512, 3.592)	0.541
GEE
No RAI therapy	Reference		Reference
RAI therapy	0.498 (0.395, 0.606)	<0.001	0.387 (0.278, 0.538)	<0.001
LNM negative
No RAI therapy	Reference		Reference
RAI therapy	0.623 (0.545, 0.713)	<0.001	0.700 (0.462, 1.062)	0.094
LNM positive
No RAI therapy	Reference		Reference
RAI therapy	0.539 (0.443, 0.654)	<0.001	0.498 (0.356, 0.697)	<0.001
No distant metastases
No RAI therapy	Reference		Reference
RAI therapy	0.603 (0.538, 0.676)	<0.001	0.644 (0.479, 0.865)	0.003
Distant metastases
No RAI therapy	Reference		Reference
RAI therapy	0.418 (0.262, 0.669)	<0.001	0.378 (0.209, 0.683)	0.001

Note:

* P-values calculated by multivariate Cox analysis.

Abbreviations: aHR, adjusted hazard ratio (adjusted for age at diagnosis, sex, race, region, tumor size, extension, lymph nodes metastases, distant metastases, radiotherapy and surgery); MEE, minimal extrathyroidal extension; GEE, gross extrathyroidal extension; LNM, lymph nodes metastases; RAI, radioactive iodine.

Figure 1 Stratification of patients based on tumor size, tumor extension, age, lymph node and distant metastases.

Abbreviation: LNM, lymph node metastasis.

Figure 2 DSS curves of multivariate Cox analysis in the group with tumors <2 cm. DSS is based on radioactive isotope in (A) patients with intrathyroidal extension; (B) patients with minimal extrathyroidal extension; (C) patients with gross extrathyroidal extension; (D) patients younger than 45 years; (E) patients older than 45 years; (F) patients without lymph node metastases; (G) patients with lymph node metastases; (H) patients without distant metastases; (I) patients with distant metastases.

Abbreviations: aHR, adjusted hazard ratios; DSS, disease-specific survival.

Figure 3 DSS curves of multivariate Cox analysis in the group with tumors >2 cm. DSS is based on radioactive isotope in (A) patients with intrathyroidal extension; (B) patients with minimal extrathyroidal extension; (C) patients with gross extrathyroidal extension; (D) patients younger than 45 years; (E) patients older than 45 years; (F) patients without lymph node metastases; (G) patients with lymph node metastases; (H) patients without distant metastases; (I) patients with distant metastases.

Abbreviations: aHR, adjusted hazard ratios; DSS, disease-specific survival.