Ability of FDG-PET to detect all cancers in patients with familial adenomatous polyposis, and impact on clinical management

Purpose Familial adenomatous polyposis (FAP) is characterised by colonic and duodenal adenomatous polyps that carry a risk of malignant transformation. Malignant degeneration of duodenal adenomas is difficult to detect. We speculated that 2-(¹⁸F)-fluoro-2-deoxy-d-glucose positron emission tomography (FDG-PET) might be able to detect early duodenal cancer in FAP. Accordingly, we investigated the role of FDG-PET in the management of FAP patients.Methods FDG-PET was performed in 24 FAP patients. Eight had advanced duodenal adenomas (Spigelman IV), including two patients with duodenal cancer. Scans were defined as positive on the basis of focal FDG accumulation.Results Pathological FDG accumulation was absent in 19 of 24 patients. All six patients with Spigelman IV duodenal adenomas (without cancer) were negative; two of these underwent a duodenectomy and pathological examination did not reveal duodenal cancer. In five patients, FDG-PET revealed significant uptake, in the duodenum (2), lower abdomen (1), lung (1) and multiple sites in the abdomen (1). These hot spots correlated with duodenal cancer (2), abdominal metastasis (1) and sclerosing haemangioma of the lung (1). We failed to make a histopathological diagnosis in the single patient with multiple intra-abdominal sites of FDG uptake. None of the patients from the FDG-PET-negative group developed cancer during follow-up (mean 2.8 years).Conclusion FDG-PET detected all the cancers present, and none of the patients with negative FDG-PET developed cancer. This suggests that positive FDG-PET in FAP patients should lead to further examinations to rule out cancer. In patients with negative FDG-PET a more conservative approach seems justified.