Differential Roles of 18F-FDG PET in Patients with Locoregional Advanced Nasopharyngeal Carcinoma After Primary Curative Therapy: Response Evaluation and Impact on Management

Sheng-Chieh Chan; Tzu-Chen Yen; Shu-Hang Ng; Chien-Yu Lin; Hung-Ming Wang; Chun-Ta Liao; Kang-Hsing Fan; Joseph Tung-Chieh Chang

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FIGURE 1.
Categorization of level of uptake of ¹⁸F-FDG at primary site. (A) Mild accumulation of ¹⁸F-FDG (score of 1; arrow). (B) Equivocal increase in ¹⁸F-FDG accumulation (score of 2; arrow). (C) Probably abnormal increase in ¹⁸F-FDG uptake (score of 3; arrow). (D) Definitely abnormal accumulation of ¹⁸F-FDG (score of 4; arrow).
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FIGURE 2.
Data for 63-y-old patient with stage IVa NPC 3 mo after CCRT. Images from unenhanced (A) and enhanced (B) axial T1-weighted MRI revealed mild symmetric mucosal thickening at nasopharynx, suggestive of postradiation change (arrows). (C) Corresponding ¹⁸F-FDG PET image revealed hypermetabolic lesion in nasopharynx, indicative of residual tumor (arrow). Biopsy revealed residual NPC.
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FIGURE 3.
Data for 49-y-old patient with stage III NPC 3 mo after CCRT. (A) Whole-body maximum-intensity projection image from ¹⁸F-FDG PET revealed scattered hypermetabolic lesions in bilateral lung fields and left pulmonary hilar region (arrow). Lung metastases and left hilar nodal metastasis were suspected. (B) Chest CT was performed for confirmation. Contrast-enhanced transaxial image revealed small left hilar lymph node, suggestive of reactive lymphadenopathy (arrow). (C) Transaxial CT image at lung window revealed peribronchial infiltrations in right middle and lower lobes as well as bilateral pleural effusion. Inflammatory disease was diagnosed. (D) Follow-up PET scan 9 mo later without treatment showed complete disappearance of hypermetabolic lesions.
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FIGURE 4.
Data for 57-y-old patient with stage IVa NPC 3 mo after CCRT. Images from unenhanced (A) and enhanced (B) axial T1-weighted MRI revealed bulky soft-tissue mass (arrows) in nasopharynx with marrow replacement in underlying skull base, suggestive of residual tumor. (C) Corresponding PET image revealed no abnormal uptake of ¹⁸F-FDG in this area. Lesion regressed on subsequent MRI scans.

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TABLE 1

Patient Characteristics (n = 131)

Characteristic^*	Stage III (group A)	Stage IVa-b (group B)	P
No. of patients	71	60
Age (y), mean ± SD	48 ± 12	L51 ± 13	0.33
Sex			0.56
Male	48	44
Female	23	16
Cell type			0.78
WHO type II	24	17
WHO type III	47	43
Curative treatment
CCRT	71	60
Induction chemotherapy		30

↵* Data are reported as number of patients, unless otherwise indicated.

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TABLE 2

Results of ¹⁸F-FDG PET and CWU in Evaluating Treatment Response Based on Site

Site	Group	Evaluation method	FN	TP	TN	FP	% Sensitivity (95% CI)	% Sensitivity (95% CI)	% Sensitivity (95% CI)
Local	A	¹⁸F-FDG PET	0	1	69	1	100	98.6 (92.3−100.0)	98.6 (92.4−100.0)
		CWU	1	0	68	2	0	97.1 (90.1−99.7)	95.8 (88.1−99.1)
	B	¹⁸F-FDG PET	0	4	55	1	100	98.2 (90.4−100.0)	98.3 (91.1−100.0)
		CWU	1	3	48	8	75.0 (19.4−99.4)	85.7 (73.8−93.6)	85.0 (73.4−92.9)
Regional lymph node	A	¹⁸F-FDG PET	0	3	65	3	100	95.6 (87.6−99.1)	95.8 (88.1−99.1)
		CWU	2	1	64	4	33.3 (0.8−90.6)	94.1 (85.6−98.4)	91.5 (82.5−96.8)
	B	¹⁸F-FDG PET	0	3	55	2	100	96.5 (87.9−99.6)	96.7 (88.5−99.6)
		CWU	1	2	53	4	66.7 (9.4−99.2)	93.0 (83.0−98.1)	91.7 (81.6−97.2)
Distant	A	¹⁸F-FDG PET	0	0	66	5	NA	93.0 (84.3−97.7)	93.0 (84.3−97.7)
		CWU	0	0	70	1	NA	98.6 (92.4−100.0)	98.6 (92.4−100.0)
	B	¹⁸F-FDG PET	1	4	54	1	80.0 (28.4−99.5)	98.2 (90.3−100.0)	96.7 (88.5−99.6)
		CWU	3	2	54	1	40.0 (5.3−85.3)	98.2 (90.3−100.0)	93.3 (83.8−98.2)
Overall	A	¹⁸F-FDG PET	0	4	200	9	100	95.7 (92.0−98.0)	95.8 (92.1−98.0)
		CWU	3	1	202	7	25.0 (0.6−80.6)	96.7 (93.2−98.6)	95.3 (91.5−97.7)
	B	¹⁸F-FDG PET	1	11	164	4	91.7 (61.5−99.8)	97.6 (94.0−99.3)	97.2 (93.6−99.1)
		CWU	5	7	154	14	58.3 (27.7−84.8)	91.7 (86.4−95.4)	89.4 (84.0−93.5)

CI = confidence interval; NA = not available.

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TABLE 3
Clinical Impact of ¹⁸F-FDG PET on Management of 131 Patients with NPC After Curative Treatment
No. (%) of patients with the following impact:
Group No. of patients Negative No change Positive
A 71 8 (11) 59 (85) 3 (4)
B 60 3 (5) 34 (57) 23 (38)

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TABLE 4

Changes in Treatment Management Attributable to ¹⁸F-FDG PET and Its Associated Clinical Impact

		Scan findings		Final diagnosis	Management plan		Follow-up time (mo)	Final status^*
Patient(s)	Group	CWU	PET	Final diagnosis	Before PET	After PET	Follow-up time (mo)	Final status^*	Impact	Remarks^*
1	A	CR	LRF	LRF	iFU	CST	16	NED	P
2	A	CR	RF	RF	iFU	CST	27	NED	P
3	A	SF	CR	CR	Biopsy	iFU	28	NED	P
4	A	CR	LF	CR	iFU	More iFU	35	NED	N
5	A	CR	RF	CR	iFU	Biopsy	32	AWD	N	Locoregional recurrence 30 mo later
6–9	A	CR	SF	CR	iFU	More iFU	16–28	NED	N	Pulmonary inflammation
10	A	CR	SF	CR	iFU	More iFU	15	NED	N	Inflammatory lumbar spine disease
11	A	CR	Second primary	CR	iFU	More iFU	21	NED	N	Rib fracture
12	B	CR	LF	LF	iFU	CST	6	DWD	P
13	B	CR	RF	RF	iFU	CST	10	DWD	P
14	B	CR	SF	SF	iFU	PT	20	AWD	P	Solitary hepatic metastasis
15	B	CR	SF	SF	iFU	PT	24	NED	P	Solitary bony metastasis at sacrum
16–32	B	EL or sLF	CR	CR	iFU	Less iFU	12–38	NED	P
33	B	SF	CR	CR	PT	iFU	15	NED	P
34	B	CR	Second primary	Second primary	iFU	Thyroidectomy	17	NED	P	Papillary thyroid carcinoma
35	B	CR	LF	CR	iFU	More iFU	27	NED	N	Osteoradionecrosis
36	B	CR	RF	CR	iFU	More iFU	32	AWD	N	Solitary rib metastasis 18 mo later
37	B	CR	SF	CR	iFU	More iFU	27	NED	N	Pulmonary inflammation

↵* See text for details.
CR = complete remission; CST = curative salvage treatment; EL = equivocal local lesion (score of 2); iFU = imaging follow-up; LF = local failure; LRF = locoregional failure; N = negative; P = positive; PT = palliative treatment; RF = regional failure; SF = systemic failure; sLF = suspected local failure (score of 3).