Patient characteristics
All patient characteristics are shown in Table 1. This research included 20 patients, with a median age of 43 years, ranging from 22 years to 78 years, including 12 males and 8 females. The primary lesions were evaluated in 16 patients, and the secondary lesions were evaluated in 4 patients, including 2 patients with postoperative recurrence, 1 patient with recurrence with metastasis, and 1 patient with multiple lung metastases after surgery. A total of 38 lesions were found in 20 patients, including 18 primary lesions, 8 recurrent lesions, and 12 metastatic lesions. The long diameter of all lesions ranged from 0.94-29.1 cm, including 1.5-29.1 cm for primary lesions, 2.66-13.5 cm for recurrent lesions, and 0.94-2.7 cm for metastatic lesions. Twelve patients with primary disease underwent surgical resection, 1 patient with recurrent disease underwent surgical resection accompanied by postoperative radiotherapy, and the remaining patients underwent nonsurgical treatment.
The 68Ga-DOTA-FAPI-04 vs. 18F-FDG PET/CT for detecting the lesions
The detection rate of 18F-FDG PET/CT for all lesions was 94.7% (36/38) and that of 68Ga-DOTA-FAPI-04 PET/CT for all lesions was 100% (38/38). There was no significant difference in the detection rates between them (p=0.493). The detection rates of 68Ga-DOTA-FAPI-04 and 18F-FDG PET/CT for primary lesions were both 100% (18/18). The detection rates of 68Ga-DOTA-FAPI-04 and 18F-FDG PET/CT for recurrent lesions were also both 100% (8/8). The detection rate of 68Ga-DOTA-FAPI-04 PET/CT for metastatic lesions was 100% (12/12) and 83.33% (10/12) for 18F-FDG PET/CT. There was no significant difference in the detection rate of metastatic lesions between the two imaging methods (p=0.478). 18F-FDG and 68Ga-DOTA-FAPI-04 PET/CT for the detection of lesions are shown in Table 2.
68Ga-DOTA-FAPI-04 vs. 18F-FDG PET/CT based on all lesion subtypes
The SUVmax of 68Ga-DOTA-FAPI-04 in all lesions was significantly higher than that of 18F-FDG, 13.44±10.42 vs. 3.05±1.39 (p<0.001) (Table 3). The SUVmax of 68Ga-DOTA-FAPI-04 in primary lesions was significantly higher than that of 18F-FDG, 15.27±8.77 vs. 3.32±1.51 (p<0.001) (Figure 2a, 3, Table 3). The SUVmax of 68Ga-DOTA-FAPI-04 in recurrent lesions was significantly higher than that of 18F-FDG, 18.59±16.32 vs. 3.09±0.96 (p=0.018) (Figure 2a, 4, Table 3). The SUVmax of 68Ga-DOTA-FAPI-04 in metastases was significantly higher than that in 18F-FDG, 7.29±3.26 vs. 2.61±1.42 (p<0.001) (Figure 2a, 5, Table 3).
The uptake of 68Ga-DOTA-FAPI-04 or 18F-FDG among primary, recurrent and metastatic lesions
The SUVmax of 68Ga-DOTA-FAPI-04 in primary lesions was higher than that in metastasis, 15.27±8.77 vs. 7.29±3.26, (p=0.034) (Figure 2b), and the SUVmax of 68Ga-DOTA-FAPI-04 in recurrent lesions was also higher than that in metastasis, 18.59±16.32 vs. 7.29±3.26, (p=0.015) (Figure 2b). However, the SUVmax of 68Ga-DOTA-FAPI-04 in recurrent lesions was not significantly different from that in primary lesions, 18.59±16.32 vs. 15.27±8.77, (p=0.423) (Figure 2b). There was no significant difference in the uptake of 18F-FDG between primary, recurrent and metastatic tumors, SUVmax (primary 3.32±1.51 vs. recurrent 3.09±0.96, p=0.693), (primary 3.32±1.51 vs. metastatic 2.61±1.42, p=0.176), (recurrent 3.09±0.96 vs. metastatic 2.61±1.42, p=0.153) (Figure 2b).
The uptake of 68Ga-DOTA-FAPI-04 or 18F-FDG in different histopathological lesions, the intermediate vs. the malignant and the SFT vs. the non-SFT.
Among the primary and recurrent lesions, there were 22 intermediate lesions and 4 malignant lesions. The uptake of 68Ga-DOTA-FAPI-04 in malignant lesions was significantly higher than that in intermediate lesions, SUVmax (35.78±15.44 vs. 12.72±5.86, p<0.001) (Figure 6a). There was no significant difference in 18F-FDG uptake between malignant and intermediate lesions, SUVmax (3.73±0.92 vs. 3.16±1.41, p=0.456) (Figure 6a).
There were 23 SFT lesions and 15 non-SFT lesions. The uptake of 18F-FDG in SFT lesions was significantly higher than that in non-SFT lesions, SUVmax (3.65±1.97 vs. 2.66±0.60, p=0.029) (Figure 6b). The uptake of 68Ga-DOTA-FAPI-04 in SFT lesions was higher than that in non-SFT lesions, SUVmax (14.67±12.19 vs. 11.55±6.55), but the difference was not statistically significant (p=0.374) (Figure 6b).
68Ga-DOTA-FAPI-04 PET/CT for the therapeutic evaluation of SFT
One recurrent SFT patient with a total of 5 lesions underwent more than 30 rounds of radiotherapy, and there was a significant difference in 68Ga-DOTA-FAPI-04 uptake of the recurrent lesions before and after treatment (Figure 7-8, Table 4). The interval between the two 68Ga-DOTA-FAPI-04 PET/CT examinations was approximately 5 months. There were no significant differences in the long diameter, short diameter or density of all recurrent lesions before and after treatment (Figure 8, Table 4). The tumor was assessed as stable disease (SD) based on size-based RECIST but as partial metabolic response (PMR) by PERCIST criteria[15]. The patient is in good condition thus far during follow-up. The patient's progression-free survival (PFS) was 37 months, and the overall survival (OS) was 47 months.