Comparison of 68Ga-FAPI-04 and 18F-FDG&nbsp;for the Detection of Primary Gastric Cancers and Metastasis&nbsp;

doi:10.21203/rs.3.rs-326617/v1

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Comparison of ⁶⁸Ga-FAPI-04 and ¹⁸F-FDG for the Detection of Primary Gastric Cancers and Metastasis

https://doi.org/10.21203/rs.3.rs-326617/v1

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published 23 Jul, 2021

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Introduction Early and precise diagnosis and staging of gastric cancer are important for its treatment and management. However, the low sensitivity of ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) for gastric cancer diagnosis limits its application. Currently, the tracer ⁶⁸Ga-FAPI, which targets fibroblast activation protein (FAP), is widely used to diagnose various cancers. However, the diagnostic value of ⁶⁸Ga-FAPI in gastric cancer is still unclear. In this study, we aimed to investigate the potential advantage of ⁶⁸Ga-FAPI-04 over ¹⁸F-FDG in the evaluation of gastric cancer.

Methods: Thirty-eight patients with gastric cancer (31 with adenocarcinoma and 7 with signet ring cell carcinoma) were recruited for this study. All of the participants underwent ⁶⁸Ga-FAPI-04 and ¹⁸F-FDG imaging by positron emission tomography (PET)/computed tomography (CT) or PET/magnetic resonance (MR). The results were interpreted by two experienced nuclear medicine physicians, and the maximum standardized uptake value (SUV_max) was calculated.

Results: For the detection of primary gastric cancer, the sensitivities of ⁶⁸Ga-FAPI-04 PET and ¹⁸F-FDG PET were 100% (38/38) and 81.6% (31/38), respectively. Four cases of adenocarcinoma and three cases of signet ring cell carcinoma were missed by ¹⁸F-FDG PET. The SUV_max of ⁶⁸Ga-FAPI-04 in tumors greater than 4 cm (11.0 ± 4.5) was higher than tumors less than 4 cm (4.5 ± 3.2) (P = 0.0015). The SUV_max of ⁶⁸Ga-FAPI-04 was higher in T2-4 tumors (9.7 ± 4.4) than in T1 tumors (3.1 ± 1.5) (P = 0.0002). For the detection of metastatic lesions, the sensitivities of ⁶⁸Ga-FAPI-04 PET and ¹⁸F-FDG PET in 10 patients with regional lymph node metastasis and distant metastasis were 6/10 and 5/10, respectively.

Conclusion: Compared to ¹⁸F-FDG PET, ⁶⁸Ga-FAPI-04 PET had superior potential in detecting primary gastric cancers and metastatic lymph nodes, ⁶⁸Ga-FAPI-04 PET also had a better performance on small gastric cancer detection. ⁶⁸Ga-FAPI-04 PET could provide better performance for gastric cancer diagnosis and staging.

Nuclear Medicine & Medical Imaging

Gastric adenocarcinoma

Signet ring cell carcinoma

Fibroblast activation protein

Cancer-associated fibroblasts

68Ga-FAPI-04

Gastric cancer is one of the most common malignant tumors, with a poor prognosis in East Asia and the USA [1, 2]. Although the diagnosis and treatment of gastric cancer have improved, the prognostic outcome remains suboptimal. Early diagnosis, accurate staging and quantitative evaluation of gastric cancer are important for its treatment, management, and prognosis. In the clinic, gastroscopy and imaging examinations are the main diagnostic methods for gastric cancer. Computed tomography (CT) and magnetic resonance imaging (MRI) have been used for the primary staging of gastric cancer. However, CT and MRI are anatomy-based imaging techniques that have been inadequate in staging, such as lymph node involvement and distant metastasis [3].

Positron emission tomography (PET) using ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) has been used in various cancer diagnoses and in gastric cancer detection [4, 5]. However, up to 53% of primary tumors in gastric cancer are not avid for ¹⁸F-FDG [6, 7]. Furthermore, low sensitivity in detecting lymph node metastasis limits the use of ¹⁸F-FDG in gastric cancer diagnosis [7]. Signet ring cell carcinoma and mucinous carcinoma also show lower ¹⁸F-FDG uptake and sensitivity than conventional adenocarcinoma [8-10]. Therefore, new tracers such as 3’-deoxy-3’-¹⁸F-fluorothymidine (¹⁸F-FLT) have been developed for gastric cancer [7, 11]. Since the lower uptake of ¹⁸F-FLT in gastric cancer, this tracer is not applied in clinical practice.

Currently, fibroblast activation protein (FAP), which is highly expressed in the cancer-associated fibroblasts (CAFs) of many malignant tumors, is used as a new target for tumor tracer development since CAFs are one of the most abundant stromal components in the tumor microenvironment [12]. Several tracers targeting FAP have been developed, among which ⁶⁸Ga-FAPI-04 is the most promising, with high affinity towards FAP and suitable kinetics [13-15]. ⁶⁸Ga-FAPI-04 PET has achieved good outcomes for the diagnosis and staging of several tumor types [12, 16-18]. Moreover, previous studies have shown that FAP is overexpressed in the CAFs of gastric cancer and plays an important role in the invasion and migration of gastric carcinomas [19, 20]. ⁶⁸Ga-FAPI-04 PET was used to image primary gastric carcinoma and metastatic lesions in one patient [21]. However, no research has reported the potential advantage of ⁶⁸Ga-FAPI-04 in gastric cancer diagnosis and the difference between ⁶⁸Ga-FAPI-04 and ¹⁸F-FDG.

The aim of this study was to assess the potential advantage of ⁶⁸Ga-FAPI-04 PET over ¹⁸F-FDG in the diagnosis of gastric cancer and to investigate the performance of ⁶⁸Ga-FAPI-04 in detecting lymph node metastasis in patients with gastric cancer.

Patients

Forty patients with gastric cancer were enrolled in this study. Two patients with gastric cancer recurrence were excluded. The rest 38 patients were confirmed by pathological biopsy under gastroscopy (Fig. 1). All patients received both ¹⁸F-FDG and ⁶⁸Ga-FAPI-04 PET/CT or PET/MR for tumor staging on separate days and had no antitumor treatment prior to PET scans. Twenty-nine patients received both ¹⁸F-FDG and ⁶⁸Ga-FAPI-04 PET/MR, and 9 patients received PET/CT. Patients with recurrent tumors, aged less than 18 years, or pregnant women were excluded from the study. This project was approved by the ethics committee in Huashan Hospital, Fudan University and Shanghai East Hospital, Tongji University School of Medicine, and all enrolled patients signed informed consent forms.

Radiopharmaceuticals and imaging protocols

¹⁸F-FDG and⁶⁸Ga-FAPI-04 were prepared as described previously [16, 22, 23], and both tracers were synthesized in the Radiochemistry Facility of the PET Center, Huashan Hospital, Fudan University, under a GMP environment.

PET/MR (uPMR790 TOF, United Imaging, China) or PET/CT (Biograph mCT, Siemens Healthineers, Germany; Ingenuity TF, Philips Healthcare, USA; uMI510, United Imaging, China) scanners were used in this study. Since different scanners were applied in this study, standardized uptake value (SUV) measurements generated by different devices were normalized after data collection. A NEMA IEC body phantom (Data Spectrum Corporation, Durham, NC, USA) with 6 simulated lesion spheres (diameters: 10 mm, 13 mm, 17 mm, 22 mm, 28 mm, and 37 mm) was applied for SUV normalization with 2, 4, 8, and 16 times the background activity (background activity concentration equal to 2 kBq/ml). The CT template of the NEMA IEC body phantom was prepared for the attenuation correction of PET/MR. Images of the phantom were acquired in each scanner with its own routine protocols. Correlation coefficients for the SUV were obtained through this phantom study and used to standardize the SUV measurements to those measured with Siemens Biograph mCT.

¹⁸F-FDG PET/CT or PET/MR was performed based on routine procedures for ¹⁸F-FDG PET tumor imaging [24]. Whole-body ⁶⁸Ga-FAPI-04 PET scans were obtained by PET/MR or PET/CT at 60 min after the intravenous injection of 111~ 185 MBq (3~5 mCi) of ⁶⁸Ga-FAPI-04 [12, 25]. A low-dose CT scan (120 keV, 100-120 mA) or an MR scan was collected for attenuation correction and image fusion. PET images were acquired in 3D mode and were reconstructed by the ordered subset expectation maximization 3D (OSEM 3D) method. The two PET scans were performed within 48 hours apart (1.6 ± 0.8 days, range: 1-2 days).

Data analysis

For calculation of the maximum SUV (SUV_max), circular regions of interest were drawn around the tumors on transaxial slices and automatically adapted to a three-dimensional VOI with Syngo.via software (Siemens Molecular Imaging, Hoffman Estates, Illinois, USA) at a 60% isocontour. The results of ⁶⁸Ga-FAPI-04 PET and ¹⁸F-FDG PET scans were independently evaluated by 2 experienced nuclear medicine physicians (JZ and FH) who were blinded to the clinical data and pathologic findings. Any difference of opinion between these two physicians was resolved by a consensus. For primary tumors and metastatic lesions, positive uptake was identified as areas of focal increase compared to surrounding normal tissue by a visual assessment supported by the ratio of suspicious lesions to surrounding normal tissue [16, 26].

Immunohistochemistry of FAP expression

Immunohistochemical staining of FAP was performed on the tumor tissue obtained after surgical resection in one patient with adenocarcinoma. An antibody against FAP (ab207178, Abcam) was used.

Statistical analysis

Statistical analysis was performed using Prism 7 (GraphPad Software, CA, USA) and STATA (version 15.1 StataCorp LLC) software. The comparisons of sensitivity, specificity, and accuracy for detection of gastric cancer between ¹⁸F-FDG and ⁶⁸Ga-FAPI-04 were using the McNemar’s test. Categorical variables are described as frequencies and percentages. Continuous variables are described as the mean ± standard deviation (SD). The Mann-Whitney U test was used to compare the SUV_max between different categorized groups. A P value less than 0.05 was considered statistically significant.

Patients

The clinical characteristics of the 38 patients are shown in Table 1 and Supplementary Table 1. Among 38 patients with gastric cancer (29 men and 9 women; age 63.7 ± 15.3 years; age range, 25–86 years) whose diagnosis was confirmed by pathological biopsy under gastroscopy, 31 had adenocarcinoma and 7 had signet ring cell carcinoma. After the PET evaluation, 24 patients (19 with adenocarcinoma and 5 with signet ring cell carcinoma) received surgical treatment, while the other patients received chemotherapy. Among 24 patients treated with surgery, 10 (9 with adenocarcinoma and 1 with signet ring cell carcinoma) were confirmed pathologically with regional lymph node metastasis after surgical resection. According to the depth of tumor invasion based on examination of the surgical specimen after resection, 12 patients were classified as T1 (tumor invading the lamina propria, muscularis mucosae, or submucosa), 3 patient was classified as T2 (tumor invading the muscularis propria), and 9 patients were classified as T4 (tumor invading the visceral peritoneum or adjacent structures). According to the maximum tumor diameter, 17 patients had a small tumor (≤ 4 cm in diameter), and 7 patients had a large tumor (˃ 4 cm in diameter). According to the histologic grade, 1 patient had a well-differentiated tumor, 15 patients had a moderately differentiated tumor, and 8 patients had a poorly differentiated tumor (4 adenocarcinomas and 4 signet ring cell carcinomas).

Diagnostic performance of ⁶⁸Ga-FAPI-04 and ¹⁸F-FDG PET

For the detection of primary gastric cancer, the sensitivities of ⁶⁸Ga-FAPI-04 PET and ¹⁸F-FDG PET were 100% and 82% (38/38 vs. 31/38, P = 0.016), respectively. The sensitivity of ⁶⁸Ga-FAPI-04 PET and ¹⁸F-FDG for detection of tumors less than 4 cm were 100% and 70% (17/17 vs. 12/17, P = 0.062). ⁶⁸Ga-FAPI-04 PET also exhibited a sensitivity of 100% in detecting both adenocarcinoma and signet ring cell carcinoma. In contrast, four cases of adenocarcinoma and three cases of signet ring cell carcinoma were missed by ¹⁸F-FDG PET.

Regional lymph node metastasis was confirmed by postsurgical pathology in 10 patients (10/24, 42%). With ⁶⁸Ga-FAPI-04 PET examination, 6 patients were diagnosed true positive, 13 patients true negative, 1 patient false positive and 4 false negative. And 5 patients were diagnosed true positive, 13 patients true negative, 1 patient false positive and 5 false negative with ¹⁸F-FDG. For the detection of regional lymph node metastatic lesions, the sensitivity, specificity and accuracy were 60% (6/10), 93% (13/14), and 79% (19/24) for ⁶⁸Ga-FAPI-04, respectively, and 50% (5/10), 93% (13/14), and 75% (18/24) for ¹⁸F-FDG. Comparison of the sensitivity, specificity and accuracy and of the two tracers yielded no significant difference (P ＞0.05).

Furthermore, 3 patients showed high ⁶⁸Ga-FAPI-04 uptake in distant lymph nodes (2 patients with retroperitoneal lymph nodes and another patient with clavicle and mediastinal lymph nodes) and 2 patients showed focal ⁶⁸Ga-FAPI-04 hypermetabolism in the liver, which were considered metastases by imaging techniques, while ¹⁸F-FDG uptake was neglected.

Comparison of ⁶⁸Ga-FAPI-04 and ¹⁸F-FDG uptake

The SUV_max measurements of ⁶⁸Ga-FAPI-04 and ¹⁸F-FDG in positive lesions are shown in Table 2. The SUV_max of ⁶⁸Ga-FAPI-04 in the primary tumor was similar to that of ¹⁸F-FDG (7.4 ± 5.0 vs. 6.5 ± 5.7, P = 0.3536). But the tumor-to background ratio of ⁶⁸Ga-FAPI-04, such as SUV_max tumor/blood pool, in the primary tumor was significantly higher than that of ¹⁸F-FDG (9.2 ± 5.9 vs. 5.9 ± 4.2, P = 0.0073). In the subgroup analysis of ⁶⁸Ga-FAPI-04, there was no difference of the SUV_max on different histologic type (P = 0.599) or tumor differentiation (P = 0.1575). The SUV_max of ⁶⁸Ga-FAPI-04 in tumors greater than 4 cm was higher than tumors less than 4 cm (11.0 ± 4.5 vs. 4.5 ± 3.2, P = 0.0015). The SUV_max of ⁶⁸Ga-FAPI-04 was higher in T2-4 tumors than in T1 tumors (9.7 ± 4.4 vs 3.1 ± 1.5, P = 0.0002). In the subgroup analysis of ¹⁸F-FDG, there was no significant difference of the SUV_max on different histologic type (P = 0.3523). The SUV_max of ¹⁸F-FDG in tumors greater than 4 cm was higher than tumors less than 4 cm (6.3 ± 1.8 vs. 3.6 ± 1.7, P = 0.0064). The SUV_maxwas higher in T2-4 tumors than in T1 tumors (5.6 ± 1.9 vs. 2.7 ± 0.9, P = 0.0021). The SUV_maxin poorly differentiated tumors () was significantly higher than in well and moderately differentiated tumours (6.2 ± 2.0 vs. 3.8 ± 1.9, P = 0.032).

Immunohistochemistry

One primary tumor sample obtained from one patient with gastric adenocarcinoma was assessed for FAP expression by immunohistochemistry. Stromal cells around the tumor presented prominent FAP expression, while tumor cells showed weak FAP expression (Fig. 2). ⁶⁸Ga-FAPI-04 PET showed high uptake (SUV_max = 10.2) in the primary gastric tumor of this patient.

Gastric cancer is one of the most common cancers and the third leading cause of cancer-related death worldwide [27]. Early and accurate diagnosis is extremely important for its treatment and prognosis. ⁶⁸Ga-FAPI-04 PET has achieved good outcomes for diagnosis in various tumors [12, 16-18]. These include high expression across a wide range of cancer types including several with typically low FDG‐avidity, low uptake in almost all normal tissues, where high physiological uptake can obscure primary or metastatic disease [28]. However, the usefulness of ⁶⁸Ga-FAPI-04 for the detection of primary gastric cancer remains unclear. In this study, we aimed to evaluate the usefulness of ⁶⁸Ga-FAPI-04 PET for the detection of gastric cancer compared with that of ¹⁸F-FDG PET.

Our results demonstrated the potential advantage of ⁶⁸Ga-FAPI-04 PET over ¹⁸F-FDG PET for the detection of primary gastric cancer. In all 38 patients with gastric cancer, all primary tumors were detected by ⁶⁸Ga-FAPI-04 PET. ⁶⁸Ga-FAPI-04 PET (100%, 38/38) provided better sensitivity than ¹⁸F-FDG PET (82%, 31/38), consistent with a previous study reporting that more positive lesions on other type of tumors were discovered with ⁶⁸Ga-FAPI-04 than with ¹⁸F-FDG, especially in gastric cancer [29]. In the present study, ⁶⁸Ga-FAPI-04 PET detected signet ring cell carcinoma of the stomach in one case that was missed by ¹⁸F-FDG PET (Fig. 3). Furthermore, in another patient with gastric adenocarcinoma,⁶⁸Ga-FAPI-04 displayed focal uptake in the primary tumor, whereas ¹⁸F-FDG showed slightly and diffusely elevated uptake in the gastric wall (Fig. 4). As a result, ⁶⁸Ga-FAPI-04 could provide better surgery determination for gastric cancer. Moreover, the background activity of ⁶⁸Ga-FAPI-04 was low, resulting in a higher tumor-to-background contrast than ¹⁸F-FDG.

Previous studies have shown that the sensitivity of ¹⁸F-FDG PET in the detection of gastric cancer ranges from 47% to 96% [7]. One of the reasons for this disparity may be the different histologic types of gastric cancer. ¹⁸F-FDG showed lower sensitivity and uptake in signet ring cell carcinoma and mucinous carcinoma than in conventional adenocarcinoma [8-10]. This is due to the relatively low expression level of glucose transporter 1 (GLUT-1) in signet ring cell and mucinous carcinomas [30]. These results are consistent with our finding that signet ring cell carcinoma had lower ¹⁸F-FDG uptake than adenocarcinoma, although the difference was not statistically significant. In our study,⁶⁸Ga-FAPI-04 detected 3 cases of signet ring cell carcinoma that were negative in ¹⁸F-FDG, resulting in a sensitivity of 100% (7/7) in detecting signet ring cell carcinoma and outperforming ¹⁸F-FDG (57%, 4/7). Therefore, ⁶⁸Ga-FAPI-04 PET has an obvious advantage for the detection of signet ring cell carcinoma, especially when negative with ¹⁸F-FDG. But the sensitivity of ⁶⁸Ga-FAPI-04 on signet ring cell carcinoma need larger samples to evaluate.

Tumor size is also an important factor influencing the detection rate of gastric cancer in PET scans. Nakajo et al. [31] examined the relationship between the SUV_max of primary gastric cancers and the size of visible tumors and found that the ¹⁸F-FDG uptake of primary tumors was significantly associated with tumor size. In another study, small gastric cancers were reported to be difficult to detect by ¹⁸F-FDG PET [32]. Interestingly, for detection of tumors less than 4 cm, ⁶⁸Ga-FAPI-04 PET also provided a better sensitivity than (100% vs. 70%, P = 0.062) ¹⁸F-FDG, although the difference is not significant. All 17 tumors ≤ 4 cm in size, including 5 with negative ¹⁸F-FDG uptake, were detected by ⁶⁸Ga-FAPI-04 PET in our study. The uptake of ⁶⁸Ga-FAPI-04 in small gastric cancers (≤ 4 cm in diameter) was lower than that in large gastric cancers (> 4 cm in diameter), it needs to be further confirmed whether ⁶⁸Ga-FAPI-04 PET has advantages in detecting small gastric cancers.

The depth of invasion in primary gastric cancer is essential for prognosis and therapy. The results from previous studies have shown that the SUV_max of ¹⁸F-FDG does not correlate with the degree of infiltration [31, 33, 34]. In addition, other tracers used to detect gastric cancer, such as ¹⁸F-FLT, are not suitable for evaluating the degree of infiltration in gastric cancers [31]. In our study, the SUV_max of ⁶⁸Ga-FAPI-04 in pathologically T4 tumors was significantly higher than that in T1 and T2 tumors (10.9 ± 4.3 vs. 3.8 ± 2.1, P = 0.0002). Thus, ⁶⁸Ga-FAPI-04 PET could provide insight into the degree of tumor invasion in gastric cancer.

In our patient-based analysis, the sensitivity of ¹⁸F-FDG PET for detecting regional metastatic lymph nodes was 50% (5/10), which is in line with previous studies of ¹⁸F-FDG PET for detecting lymph node metastasis (mean sensitivity: 45%) [7]. The sensitivity of ⁶⁸Ga-FAPI-04 PET for the detection of regional metastatic lymph nodes was 60% (6/10). As shown in Fig. 5, lymph node metastasis at the lesser curvature of the stomach in one patient with moderately differentiated adenocarcinoma presented elevated uptake of ⁶⁸Ga-FAPI-04 but negative uptake of ¹⁸F-FDG. Chen et al. [16] reported 12 cases of gastric cancer (4 signet ring cell carcinomas and 8 adenocarcinomas) and found that ⁶⁸Ga-FAPI-04 PET/CT showed higher sensitivity than ¹⁸F-FDG PET/CT for the detection of lymph node metastases of gastric cancer from their lesion-based analysis.

In addition, in contrast to ¹⁸F-FDG PET, ⁶⁸Ga-FAPI-04 PET has an advantage in detecting distant metastasis in gastric cancer. Although pathological analysis of a biopsy serves as the gold standard for the diagnosis of metastases in gastric cancer, the noninvasive imaging technique has become a standard modality for staging before treatment. In this study, distant lymph nodes in 3 patients showed high ⁶⁸Ga-FAPI-04 uptake but negative ¹⁸F-FDG uptake. These distant lymph nodes, which included the posterior peritoneum lymph nodes and supraclavicular lymph nodes, are prevalent metastatic sites of gastric cancer. As shown in Fig. 6, one patient displayed discernible ⁶⁸Ga-FAPI-04 uptake in the peritoneum that was not detected by ¹⁸F-FDG PET. It is known that distant metastasis has an important impact on treatment and prognosis. In gastric cancer, peritoneal metastasis is associated with a poor prognosis [35]. According to previous studies, the sensitivity of ¹⁸F-FDG PET for the detection of metastatic peritoneal disease is low [36, 37]. Overall, ⁶⁸Ga-FAPI-04 PET may play an important role in detecting metastases of gastric cancer with or without confirmation by pathological biopsy.

There were several limitations to our study. The small sample size limited the power of the analysis, and not all histological types of gastric cancer were analyzed. Moreover, as there was no histological verification available for some cases of highly suspicious distant metastases, latent bias may be present. We also intended to investigate the advantage of PET/MR in the detection of gastric cancer metastases, but it seems infeasible due to the lack of contrast-enhanced MRI data in this study. Nevertheless, the usefulness of ⁶⁸Ga-FAPI-04 PET for the detection of distant metastases of gastric cancer needs to be further investigated on a larger cohort.

In summary, ⁶⁸Ga-FAPI-04 PET presents superior potential in detecting primary gastric cancers and metastatic lymph nodes than ¹⁸F-FDG PET. And for tumor size less than 4 cm, ⁶⁸Ga-FAPI-04 PET can also provide a better sensitivity. The SUV_max of ⁶⁸Ga-FAPI-04 was higher in T2-4 gastric cancers than in T1 gastric cancers, indicating its potential role in the assessment of the degree of gastric cancer invasion. ⁶⁸Ga-FAPI-04 PET could be a better method for gastric cancer diagnosis and staging. Nonetheless, it is still necessary to evaluate the potential role of ⁶⁸Ga-FAPI-04 in gastric cancer in a larger cohort.

Author contribution

FX, JZ, YG, FH designed this study and organized the data collection, FX, DJ, XC, ZY, HW, XZ, XL, SR, QH collected the data, DJ, HW, QH processed and analyzed the data, FX and DJ lead the manuscript writing, all authors reviewed and revised the manuscript.

Acknowledgments

The authors appreciate the excellent technical assistance of the staff at the PET Center, Huashan Hospital, Fudan University, and the staff at the Department of Nuclear Medicine, Shanghai East Hospital, Tongji University School of Medicine.

Funding information

This work was supported by the National Natural Science Foundation of China (81801752), Shanghai Sailing Program (20YF1404400), Startup Fund of Huashan Hospital, Fudan University (2017QD081), Shanghai Municipal Key Clinical Specialty (shslczdzk03402), Shanghai Municipal Science and Technology Major Project (No. 2018SHZDZX01), and Shanghai Municipal Health Commission Fund (202040420).

Compliance with ethical standards

Disclosure/Conflict of Interest

None.

Research involving human participants

All procedures performed in this study involving human participants were n accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards.

Consent to participate

Informed consent was obtained from all participants.

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Table 1: Clinical and pathological characteristics of patients

N = 38	Overall
Age (years)
Mean (SD)	63.7 (15.3)
Median [min, max]	67.5 [25.0, 86.0]
Sex
Male	29
Female	9
Type
Adenocarcinoma	31
Signet ring cell carcinoma	7
Treatment
Surgery	24
Chemotherapy	5
None	5

Table 2: Relationships between pathological factors and the uptake of ⁶⁸Ga-FAPI-04 or ¹⁸F-FDG in positive lesions

	⁶⁸Ga-FAPI-04			¹⁸F-FDG
	No.	SUV_max	P	No.	SUV_max	P
All	38	7.4 ± 5.0		31	6.5 ± 5.7
Histologic type
AC	31	7.5 ± 5.0	0.599	27	6.9 ± 5.9	0.3523
SRCC	7	6.7 ± 5.1		4	3.8 ± 2.3
Tumor size (cm)
≤ 4	17	4.5 ± 3.2	0.0015	12	3.6 ± 1.7	0.0064
> 4	7	11.0 ± 4.5		6	6.3 ± 1.8
Depth of invasion
T1	12	3.1 ± 1.5	0.0002	7	2.7 ± 0.9	0.0021
T2, T3 and T4	12	9.7 ± 4.4		11	5.6 ± 1.9
Degree of differentiation
Well and moderately	16	5.2 ± 3.4	0.1575	13	3.8 ± 1.9	0.032
Poorly	8	9.0 ± 6.0		5	6.2 ± 2.0

Twenty-four patients (19 with adenocarcinoma and 5 with signet ring cell carcinoma) who received surgical treatment had detailed pathology results.

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published 23 Jul, 2021

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Editorial decision: Major Revision
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Comparison of ⁶⁸Ga-FAPI-04 and ¹⁸F-FDG for the Detection of Primary Gastric Cancers and Metastasis

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Comparison of 68Ga-FAPI-04 and 18F-FDG for the Detection of Primary Gastric Cancers and Metastasis

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Comparison of ⁶⁸Ga-FAPI-04 and ¹⁸F-FDG for the Detection of Primary Gastric Cancers and Metastasis