JHSGR16th April 2011

Dr Lee Man Kit Derek

The value of PET in staging adenocarcinoma (e.g. colorectal cancer) is well established

Tomoharu T. et al. The American J of Surg. 2002; 184: 433-436

Not as straight forward as other tumors in knowing where PET-CT fits into management

HCC accumulate FDG to varying degrees

Conventional F-FDG PET has a high average false-negative rate of 40-50% in the detection of HCC

Delbeke et al. Arch Surg. 1998;133:510-515Khan et al. J Hepatol. 2000;32:792-797

Okazumi et al. J Nucl Med. 1992;33:333-339

Questions to be answered:1. Ability to differentiate benign and

malignant liver lesions2. Detection of intra-hepatic tumors +/-

metastasis3. Detection of extra-hepatic metastasis

• Recent studies suggested the use of another tracer, C-acetate, in conjunction with F-FDG to increase the detection rate of HCC

• The degree of HCC differentiation determines its relative avidity for one of the two probe molecules

Ho et al.

F-FDG C-acetate

Well differentiated HCC - +

Poorly differentiated HCC

+ -

C-acetate is able to detect the entire proportion of HCC lesions that are negative on F-FDG imaging

Tumors that are both positive on C-acetate and F-FDG are taken up by different parts of tumors

Well differentiated HCC

Poorly differentiated HCC

Moderately differentiated HCC

Dual-tracers PET are complementary to each other in the detection of HCC

The addition of C-acetate to F-FDG PET-CT increases the overall sensitivity for the detection of primary HCC

Park et al.

F-FDG C-acetate Dual tracer

Sensitivity (%) 60.9 75.4 82.7

Dual-tracers PET can be quite specific for HCC (Ho et al.) Useful in the preliminary evaluation of unknown liver

massesC-acetate

F-FDG

+ + HCC is likely

- + Non HCC malignancy or poorly differentiated HCC

- - Benign pathology is more likely

Although dual-tracers PET has a high sensitivity in detecting HCC

Limitation in diagnosing small tumor (<2cm HCC)

Park et al.

Dual tracer PET-CT appear not to be useful for the detection of small lesions (<2cm) in the liver

Particularly useful when patients come in for post-op follow up Imaging of liver : no recurrence of tumor Alpha fetoprotein : ↑ trend

Extra-hepatic metastasis Lung Bone Adrenal gland Abdominal peritoneum Brain

F-FDG PET has only a fair sensitivity in diagnosis of primary HCC

Studies have reported that F-FDG PET may have its role in detection of HCC secondary tumors

Bohm et al. J Cancer Res Clin Oncol. 2004;130:266-272Sugiyama et al. J Gastroenterol. 2004;39:961-968

Dual-tracers PET can detect extra-hepatic metastatic tumor diameter >1cm For tumor 1-2cm, FDG is more sensitive than C-acetate,

although the difference is not statistically significant

For metastatic HCC, dual tracer PET-CT was not superior to FDG alone

I : Primary HCC FDG avidII : Primary HCC C-acetate avidIII : Primary HCC both tracers avidIV : no baseline PET for primary tumor characterisation

6 lesions both tracers avid

12 lesions both tracer avid

44 lesions both tracer avid

23% of metastatic lesions were detected by C-acetate only

NPV of single-tracer PET <50% Negative single-tracer cannot reliably exclude

metastatic HCC Dual-tracers PET had an incremental value when

compare with single-tracer PET in the evaluation of HCC metastasis

Questions to be answered: Ability to differentiate benign and

malignant liver lesions• Dual-tracers PET has high specificity for

detection of liver masses (benign vs malignant)

• F-FDG PET alone has poor sensitivity in detecting primary HCCThe addition of C-acetate to F-FDG PET

increases overall sensitivity

Questions to be answered: Detection of intra-hepatic tumors +/-

metastasis• Dual-tracer PET has the limitation in detecting

intra-hepatic HCC <2cm

• Other imaging modality i.e. Primovist ®-enhanced MRI can be used Able to detect small liver metastases (<1cm)

Kim et al. AJR Am J Roentgenol. 2009 Jun;192(6):1675-81

Questions to be answered: Detection of extra-hepatic metastasis

• F-FDG PET has a relatively high sensitivity for detection of extra-hepatic metastasis HCC

• Dual-tracer PET demonstrate complementary role in the detection of extra-hepatic metastasis HCC

PET-CT has to be seen as part of the work up and not a complete replacement of other imaging modalities for detecting HCC USG Triple phase multi-detector CT Primovist ®-enhanced MRI