Diagnostic value of [Ga]Ga-FAPI-04 in patients with colorectal cancer in comparison with [F]F-FDG PET/CT.

PURPOSE

This study aimed to compare the diagnostic performance of [Ga]Ga-FAPI-04 PET/CT and [F]F-FDG PET/CT in primary and metastatic colorectal cancer (CRC) lesions.

METHODS

This single-center preliminary clinical study (NCT04750772) was conducted at the Peking University Cancer Hospital & Institute and included 61 participants with CRC who underwent sequential evaluation through PET/CT with [F]F-FDG and [Ga]Ga-FAPI-04. Their PET/CT images were analysed to quantify the uptake of the two tracers in the form of maximum standardised uptake (SUV) values and target-to-background ratio (TBR), which were then compared using Wilcoxon's signed-rank test. The final changes in the tumour-node-metastasis (TNM) stage of all participants were recorded.

RESULTS

Of all the participants, 21 were treatment naïve and 40 had been previously treated. In primary CRC lesions, the average TBRs of [Ga]Ga-FAPI-04 and [F]F-FDG were 13.3 ± 8.9 and 8.2 ± 6.5, respectively. The SUV of [Ga]Ga-FAPI-04 in signet-ring/mucinous carcinomas (11.4 ± 4.9) was higher than that of [F]F-FDG (7.9 ± 3.6) ( = 0.03). Both median SUV in peritoneal metastases and TBR in liver metastases of [Ga]Ga-FAPI-04 were higher than those of [F]F-FDG (5.2 vs. 3.8, < 0.001; 3.7 vs. 1.9, < 0.001, respectively). Compared with [F]F-FDG PET/CT, clinical TNM staging based on [Ga]Ga-FAPI-04 PET/CT led to upstaging and downstaging in 10 (16.4%) and 5 participants (8.2%), respectively. Therefore, the treatment options were changed in 13 participants (21.3%), including 9 with additional chemo/radiotherapy and/or surgery and others with avoidance or narrowed scope of surgery.

CONCLUSION

[Ga]Ga-FAPI-04 showed potential as a novel PET/CT tracer to detect lymph nodes and distant metastases, which improved CRC staging, thus prompting the optimisation or adjustment of treatment decisions.