- Design
- Dual-centre retrospective diagnostic association study
- Population
- 64 adults with 65 colorectal primary lesions who had FAPI-42 PET/CT before surgery
- Primary outcome
- Association of PET uptake with tumour budding grade
- Effect
- SUVmax 12.66 vs 10.16 (P = 0.012); BMI plus SUVmax AUC 0.841 (95% CI 0.731 to 0.934)
This dual-centre retrospective study included 64 adults (65 primary lesions) who had [18F]FAPI-42 PET/CT before colorectal cancer surgery. The reference standard was surgical pathology, including tumour budding grade.
Intermediate or high-grade budding lesions had higher SUVmax than low-grade lesions (12.66 ± 3.36 against 10.16 ± 3.86; P = 0.012). A model combining body mass index and SUVmax had an AUC of 0.841 (95% CI 0.731 to 0.934), 0.830 after correction for optimism.
The authors state that independent multicentre external validation is needed before clinical use. FAPI tracers are not part of routine colorectal staging, and tumour budding is usually graded on resection or biopsy. The study is a signal for further work.
- FAPI PET is not a substitute for pathology grading of tumour budding.
- Treat the SUVmax difference as an association; the groups overlapped.
- Account for body mass index when comparing uptake across patients.
- Do not request FAPI PET for budding assessment outside a research setting.
Why it matters
A noninvasive marker of aggressive biology before surgery would help plan treatment, if it holds up.
Don't overread it
Retrospective, 64 patients and internal validation only: this does not support clinical use of FAPI PET to grade budding.
The statistics, in plain English
The SUVmax values of the two groups overlapped widely (standard deviations of about 3.4 to 3.9 around means of 10 to 13), so a single scan cannot sort an individual patient reliably. The optimism-corrected AUC of 0.830 is better than the raw figure but is still from the same 64 patients.
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