Table 3.

Univariable and multivariable Cox analysis of overall survival by clinical and tumor characteristics

Prognostic Factor	N	Events	HR	95% CI	p-value
Age
≤52 (ref)	30	10	-	-	-
>52	29	10	1.39	(0.56, 3.47)	0.478
Sex
Female (ref)	33	9	-	-	-
Male	26	11	0.93	(0.35, 2.44)	0.883
ATF4 protein
High (ref)	26	3	-	-	-
Low	33	17	6.21	(1.81, 21.28)	0.004
ATF4 copy number
2N (ref)	35	6	-	-	-
Loss, 0N/1N	24	14	3.26	(1.25, 8.54)	0.016
RET M918T mutation
Negative (ref)	34	9	-	-	-
Positive	23	11	1.49	(0.62, 3.61)	0.376
pT category
T1 (ref)	13	2	-	-	-
T2	12	2	0.57	(0.08, 4.14)	0.581
T3	16	5	1.51	(0.29, 7.92)	0.626
T4a	16	10	2.54	(0.53, 12.08)	0.242
pN category
N0 (ref)	13	0	-	-	-
N1	44	20	11.52	(1.57, 1467.52)	0.009
M category
M0 (ref)	35	8	-	-	-
M1	24	12	1.50	(0.59, 3.84)	0.395
Extrathyroidal invasion
No (ref)	27	6	-	-	-
Yes	18	6	1.26	(0.40, 3.96)	0.692
Stage^
I (ref)	5	2	-	-	-
II	4	0	0.12	(0.00, 1.49)	0.103
III	5	1	0.57	(0.05, 4.31)	0.578
IVa	16	4	0.24	(0.05, 1.51)	0.120
IVc	29	13	0.56	(0.16, 2.91)	0.437
ATF4 protein/RET mutation status*
High/negative (ref)	14	1	-	-	-
High/M918T	11	2	2.97	(0.26, 33.17)	0.378
Low/negative	20	8	10.64	(1.30, 87.10)	0.027
Low/M918T	12	9	11.66	(1.47, 92.29)	0.020
ATF4 copy number/RET mutation status*
2N/negative (ref)	21	3	-	-	-
2N/M918T	12	3	1.68	(0.33, 8.47)	0.528
0N or 1N/negative	13	6	3.79	(0.93, 15.45)	0.063
0N or 1N/M918T	11	8	4.06	(1.07, 15.41)	0.040

0N: homozygous deletion, 1N: one copy, 2N: diploid, Low: <20% expression, High: >20% expression, HR: hazard ratio, M918T: RET^M918T present, negative: absent RET^M918T mutation, Ref: reference;

^{^}AJCC 7^th edition;

^*RET mutation status specifically for M918T.