Evidence-Based PET for Abdominal and Pelvic Tumours

Evidence-based data about the usefulness of positron emission tomography (PET) and hybrid imaging methods (PET/CT and PET/MRI) in abdominal and pelvic tumours have been collected and discussed in this chapter. These data were divided in three sections: (1) gastrointestinal tumours, (2) uro-genital tumours, (3) gynaecological tumours. Several pooled data (diagnostic and prognostic data), clinical settings (e.g. staging, restaging, treatment evaluation) and radiotracers as fluorine-18 fluorodeoxyglucose (18F-FDG), radiolabelled choline and prostate-specific membrane antigen (PSMA) were considered.


Introduction
Evidence-based data about the usefulness of positron emission tomography (PET) and hybrid imaging methods (PET/CT and PET/MRI) in abdominal and pelvic tumours have been collected and discussed in this chapter. These data were divided in three sections: (1) gastrointestinal tumours, (2) uro-genital tumours, (3) gynaecological tumours. Several pooled data (diagnostic and prognostic data), clinical settings (e.g. staging, restaging, treatment evaluation) and radiotracers as fluorine-18 fluorodeoxyglucose ( 18 F-FDG), radiolabelled choline and prostatespecific membrane antigen (PSMA) were considered.

PET in Gastrointestinal Tumours
Fifty-two meta-analyses on the role of PET imaging in gastrointestinal tumours have been selected . Pooled data about PET/CT in colorectal cancer, gastric cancer, anal cancer, stromal tumours, hepato-biliary tumours, liver metastases and pancreatic cancer have been reported in Table 7.1.
One meta-analysis found a strong prognostic power of 18 F-FDG PET parameters for progression free survival (PFS) and overall survival (OS) [22]. Finally, another meta-analysis assessed the role of 18 F-FDG PET/CT in radiotherapy planning [23].

Stromal Tumours (GIST)
Two meta-analyses about the role of 18 F-FDG PET/CT in treatment evaluation and prediction of malignant potential in patients with GIST have been found and included [27,28], suggesting a role of this imaging method in these settings.

PET in Gynaecological Tumours
Thirty-three meta-analyses on the role of 18 F-FDG PET imaging in gynaecological tumours have been selected . Pooled data about 18 F-FDG PET/CT in cervical cancer, endometrial cancer, ovarian cancer and peritoneal carcinomatosis have been reported in Table 7.2.
Conversely, some meta-analyses showed sub-optimal sensitivity in N and M staging [72,77]. Only one meta-analysis showed a good prognostic power of 18 F-FDG PET/CT in ovarian cancer, with particular regard to OS [73].

Peritoneal Carcinomatosis
Three meta-analyses were focused on the role of 18

PET/MRI
Finally, recent studies evaluated the role of 18

PET in Uro-genital Tumours
Thirty-five meta-analyses on the role of PET imaging in uro-genital tumours have been selected . In particular, pooled data about radiolabelled choline, PSMA and fluciclovine PET/CT in prostate cancer and 18 F-FDG PET/CT in bladder cancer, renal cell carcinoma, testicular and penile cancer have been included (Table 7.3).

Radiolabelled Choline PET for Prostate Cancer
Several meta-analyses described a very high specificity for detection of local lymph node involvement and for detection of distant metastases of prostate cancer by using radiolabelled choline PET. Radiolabelled choline PET is also widely used in patients with suspected biochemi-  cal relapse after initial treatments, even as a guide for salvage lymph node dissection [83][84][85][86][87]. Additionally, PSA kinetics was shown to be strongly related to the detection rate in patients undergoing radiolabelled choline PET [88]. Similarly, high PSA trigger was shown to be an important risk factor for positive findings of radiolabelled choline PET/CT [89]. PET with radiolabelled choline is a well-established imaging tool in clinical practice for detection of bone metastases [90,91]. Diagnostic accuracy of radiolabelled choline PET was proven to be superior than other radiotracers as 18 F-FDG and 11 C-acetate [92], even if 11 C-acetate PET could be considered in patients with relapse [93]. 18 F-fluorocholine (FCH) PET showed higher specificity than 11 C-choline PET [94]. Conversely, the choice of 18 F-FCH or 11 C-choline might not affect the detection of metastases in restaging patients after primary surgery and/or radiotherapy [95].

Radiolabelled PSMA PET in Prostate Cancer
Radiolabelled PSMA PET showed higher detection rate than other imaging modalities in prostate cancer [96,97]. It was also proven to alter significantly the clinical management of these patients [98]. Diagnostic performance of PSMA PET was high for detection of node involvement in intermediate-and high-risk prostate cancer patients [99][100][101]. PSA kinetics may be predictor of radiolabelled PSMA PET positivity in patients with biochemical relapse [102]. PSMA detection rate ranged from 64% to 97% when PSA trigger was over 2 ng/ml at the time of scan [97].

Fluciclovine PET in Prostate Cancer
A meta-analysis demonstrated that fluciclovine ( 18 F-FACBC) PET/CT had an 87% pooled sensitivity and 66% pooled specificity in detecting prostate cancer recurrence, being a useful imaging method in this setting [115].

Incidental 18 F-FDG Uptake in the Prostate
A meta-analysis demonstrated that incidental 18 F-FDG uptake in the prostate is observed in about 2% of 18 F-FDG PET/CT scans performed in male patients carrying a significant risk of malignancy. Therefore, whenever this finding is detected further investigation is warranted to exclude malignancy [117].

Renal Cell Carcinoma
Values of sensitivity and specificity of 18 F-FDG PET/CT were 86% and 88%, respectively, for detection of recurrence [110]. If diagnostic performance of 18 F-FDG PET/CT for detection of recurrent renal and extra-renal lesions was assessed separately, sensitivity and specificity of extra-renal lesions was found superior than accuracy for renal lesions [111].

Testicular and Penile Cancer
18 F-FDG-PET sensitivity was non-optimal in the evaluation of patients with testicular cancer [112]. Similar results were drawn if PET was performed after chemotherapy treatment in patients with seminoma [113]. Clinical usefulness of 18 F-FDG PET for detection of metastatic inguinal lymph nodes in patients with penile cancer is controversial [114].