Primary Tumor 18F-FDG Avidity Affects the Performance of 18F-FDG PET/CT for Detecting Gastric Cancer Recurrence

Soo Jeong Kim; Young Seok Cho; Seung Hwan Moon; Jae Moon Bae; Sung Kim; Yearn Seong Choe; Byung-Tae Kim; Kyung-Han Lee

doi:10.2967/jnumed.115.163295

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FIGURE 1.
Representative case of ¹⁸F-FDG–avid primary tumor. (A) Preoperative PET/CT and PET images of 75-y-old patient show a gastric cancer with high ¹⁸F-FDG uptake (SUV_max, 11.9). Primary tumor was moderately differentiated tubular adenocarcinoma (4.5 × 4 × 0.6 cm) located in center of high body and posterior wall. (B) Follow-up PET/CT and PET images 27 mo later demonstrated increased ¹⁸F-FDG uptake in mesenteric lymph node (SUV_max 7.5) that was confirmed to be recurrent disease by radiologic studies.
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FIGURE 2.
Representative case of ¹⁸F-FDG–nonavid primary tumor. (A) Preoperative PET/CT and PET images of 38-y-old patient showed gastric cancer without visually discernable ¹⁸F-FDG uptake. CT findings show diffuse thickening involving most of the stomach wall (arrowheads). Primary tumor was poorly differentiated tubular adenocarcinoma (14 × 13 cm) located in body and anterior wall. (B) Follow-up PET/CT and PET images 10 mo later failed to detect any suggestive ¹⁸F-FDG uptake, but recurrence in right ovary (arrow) was pathologically confirmed.
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FIGURE 3.
Relation between primary tumor and recurrent lesion ¹⁸F-FDG avidity. (A) Scatterplot comparing distribution of recurrent lesion SUV_max between patients with ¹⁸F-FDG–avid and –nonavid primary tumors. (B) Correlation analysis between recurrent lesion SUV_max and primary gastric tumor. LN = lymph node.

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TABLE 1

Clinical Characteristics of 368 Study Subjects with Advanced Gastric Cancer

Characteristic	All subjects (n = 368)	¹⁸F-FDG–avid tumor group^* (n = 236)	¹⁸F-FDG–nonavid tumor group^† (n = 132)	P
Mean age ± SD (y)	57.8 ± 11.6	60.2 ± 10.9	53.5 ± 11.6	<0.001^‡
Male (%)	250 (67.9)	171 (72.5)	79 (59.8)	0.013^¶
Lauren classification
Intestinal	146 (39.7)	116 (49.2)	30 (22.7)	<0.001^¶
Diffuse	162 (44.0)	84 (35.6)	78 (59.1)	<0.001^¶
Indeterminate	15 (4.1)	13 (5.5)	2 (1.5)	0.063^¶
Mixed	45 (12.2)	23 (9.7)	22 (16.7)	0.052^¶
Signet ring cell	51 (13.9)	19 (8.1)	32 (24.2)	<0.001^¶
Nonsignet ring cell	317 (86.1)	217 (91.9)	100 (75.8)
Mean tumor size ± SD (cm)	6.0 ± 3.3	6.2 ± 2.9	5.7 ± 3.8	0.279^‡
T2	181 (49.2)	104 (44.1)	77 (58.3)	0.009^¶
T3	123 (33.4)	86 (36.4)	37 (28.0)	0.101^¶
T4a	60 (16.3)	42 (17.8)	18 (13.6)	0.300^¶
T4b	4 (1.1)	4 (1.7)	0 (0.0)	0.301^§
N0	135 (36.7)	68 (28.8)	67 (50.8)	<0.001^¶
N1	66 (17.9)	51 (21.6)	15 (11.4)	0.014^¶
N2	74 (20.1)	52 (22.0)	22 (16.7)	0.218^¶
N3a	60 (16.3)	43 (18.2)	17 (12.9)	0.183^¶
N3b	33 (9.0)	22 (9.3)	11 (8.3)	0.750^¶

↵* Initial primary gastric tumor uptake (+) and SUV_max ≥ 4.
↵† Initial primary gastric tumor uptake (−) or SUV_max < 4.
↵‡ t test.
↵¶ Pearson χ² test.
↵§ Fisher exact test.
Data in parentheses are percentages.

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TABLE 2

Gastric Cancer Recurrence and Diagnostic Performance of ¹⁸F-FDG PET

Parameter	All subjects (n = 368)	¹⁸F-FDG–avid tumor group^* (n = 236)	¹⁸F-FDG–nonavid tumor group^† (n = 132)	P
Recurrence (%)	72 (19.6)	46 (19.5)	26 (19.7)	0.962^‡
Mean duration to recur ± SD (mo)	18.9 ± 13.3	17.3 ± 13.3	21.8 ± 12.9	0.167^¶
Follow-up PET scans within 3 mo of clinical decision of recurrence (%)	63	42	21	0.645^‡
PET sensitivity for recurrence (%)
Including all recurrences	45/63 (71.4)	34/42 (81.0)	11/21 (52.4)	0.018^‡
Excluding recurrences in remnant stomach or anastomosis site	41/58 (70.7)	32/39 (82.1)	9/19 (47.4)	0.006^‡
Follow-up PET scans without recurrence	514	310	204
PET specificity for recurrence	97.3%	97.1%	97.5%	0.758^‡