While computed tomography (CT), magnetic resonance imaging (MRI) and 18F-fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) are more commonly utilized for the detection of ovarian cancer, emerging research suggests that 68Ga-fibroblast activation protein inhibitor (FAPI) PET/CT may be a viable imaging alternative.
For a new meta-analysis, recently published in Academic Radiology, researchers reviewed data from five studies, published between 2023 to 2024, that examined the use of 68Ga-FAPI PET in 206 patients with ovarian cancer.
The study authors found that 68Ga-FAPI PET CT/MR had a 90 percent pooled sensitivity rate and a 95 percent pooled specificity rate for ovarian cancer.
Additionally, the researchers pointed out that the PET agent demonstrated 94 percent sensitivity and 95 percent specificity for metastatic lymph nodes.
“Compared to 18F-FDG, 68Ga-FAPI offers several advantages, such as lower uptake in normal organs (except skeletal muscle), increased uptake of the tracer in metastatic lesions and decreased background activity,” wrote lead study author Lixin Sun, M.D., who is affiliated with the Department of Nuclear Medicine at Beijing Luhe Hospital and Capital Medical University in Beijing, China, and colleagues.
While cautioning about the possibility of false negatives with 68Ga-FAPI PET CT/MRI due to small lesions and abdominal movement, the meta-analysis authors found the use of 68Ga-FAPI PET CT/MRI exhibited 93 percent sensitivity and 96 percent specificity for peritoneal carcinomatosis.
Three Key Takeaways
1. High diagnostic accuracy. The meta-analysis found that 68Ga-FAPI PET CT/MR demonstrated a 90 percent pooled sensitivity and 95 percent specificity for detecting ovarian cancer, with particularly strong performance in identifying metastatic lymph nodes (94 percent sensitivity, 95 percent specificity) and peritoneal carcinomatosis (93 percent sensitivity, 96 percent specificity).
2. Advantages over 18F-FDG PET. Compared to 18F-FDG PET, 68Ga-FAPI PET exhibits lower uptake in normal organs, higher uptake in metastatic lesions, and improved background contrast.
3. Can targeted use of 68Ga-FAPI PET overcome limitations? While researchers cautioned about the possibility of false negatives due to small lesions and abdominal movement, the use of stroma-targeted PET may enhance detection of smaller lesions.
Emphasizing research that has shown a buildup of 68Ga-FAPI in PET imaging of malignancies that may have low uptake of FDG, the meta-analysis authors suggest that more targeted use of 68Ga-FAPI may bolster the agent’s detection of smaller lesions.
“It is expected that stroma-targeted PET will have a higher innate sensitivity compared to glycolysis-targeted PET to identify tiny lesions since FAPI targets the tumor stroma. Furthermore, 68Ga-FAPI exhibits extremely low intestine physiologic uptake, resulting in strong target-to-background contrast and distinct detection of tiny peritoneal foci,” pointed out Sun and colleagues,” pointed out Sun and colleagues.
(Editor’s note: For related content, see “SNMMI: New Study Suggests Merits of FAPI PET/CT for Breast Cancer Staging,” “Consensus Recommendations on MRI, CT and PET/CT for Ovarian and Colorectal Cancer Peritoneal Metastases” and “Multicenter Study Shows Merits of AI-Powered Ultrasound Assessment for Detecting Ovarian Cancer.”)
In regard to limitations of the meta-analysis, the authors conceded that all the review studies were completed in China, possibly limiting extrapolation of the meta-analysis findings to broader populations. They also noted limited research to assess the impact of 68Ga-FAPI PET CT/MR in initial staging and restaging for ovarian cancer.
