Significant value of 18F-FDG-PET/CT in diagnosing small cervical lymph node metastases in patients with nasopharyngeal carcinoma treated with intensity-modulated radiotherapy

Table 2 Metastatic rates of small cervical lymph nodes based on MRI and PET/CT findings

Level	Group A (≥ 5 and < 6 mm)		Group B (≥ 6 and < 7 mm)		Group C (≥ 7 and < 8 mm)		Group D (≥ 8 and < 9 mm)		Group E (≥ 9 and < 10 mm)		P ^e
Level	Total^a	Metastatic lymph nodes (%)^b	Total^a	Metastatic lymph nodes (%)^b	Total^a	Metastatic lymph nodes (%)^b	Total^a	Metastatic lymph nodes (%)^b	Total^a	Metastatic lymph nodes (%)^b	P ^e
I^c	197	0 (0)	70	0 (0)	34	2 (5.9)	10	2 (20.0)	3	3 (100.0)	< 0.001
II	396	17 (4.3)	329	30 (9.1)	263	80 (30.4)	167	94 (56.3)	111	91 (82.0)	< 0.001
III/Va	170	8 (4.7)	91	8 (8.8)	58	23 (39.7)	34	24 (70.6)	12	11 (91.7)	< 0.001
IV/Vb	45	3 (6.7)	36	4 (11.1)	19	12 (63.2)	26	22 (84.6)	11	10 (90.9)	< 0.001
P ^d₁	0.018		0.005		< 0.001		0.001		0.487
P ^d₂	0.768		0.915		0.008		0.011		0.503

MRI magnetic resonance imaging, PET/CT positron emission tomography/computed tomography
^aTotal number of small cervical lymph nodes based on MRI findings
^bThe number of metastatic small cervical lymph nodes based on PET/CT findings
^cThere were 184 (93.4%) in the level Ib and 13 (6.6%) in the level Ia for group A. No small cervical lymph nodes were observed in level Ia for the other groups
P ^d₁ : Comparison between levels I, II, III/Va, and IV/Vb; P ^d₂ : Comparison between levels II, III/Va, and IV/Vb
^eComparison between groups A, B, C, D and E. P values are calculated by Chi square test or Fisher’s exact test

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