Update of PET and PET/CT for hepatobiliary and pancreatic malignancies

Abstract

Evaluation of patients with known or suspected recurrent colorectal carcinoma is now an accepted indication for FDG PET imaging. FDG PET does not replace imaging modalities such as CT for preoperative anatomic evaluation, but is indicated as the initial test for diagnosis and staging of recurrence, and for preoperative staging (N and M) of known recurrence that is considered to be resectable. FDG PET imaging is valuable for differentiation of post-treatment changes from recurrent tumor, differentiation of benign from malignant lesions (indeterminate lymph nodes, hepatic and pulmonary lesions) and evaluation of patients with rising tumor markers in the absence of a known source. FDG PET has an impact on the treatment of 25%–30% of patients. Addition of FDG PET to the evaluation of these patients reduces overall treatment costs by accurately identifying patients who will and will not benefit from surgical procedures. FDG PET imaging seems promising for monitoring patient response to therapy, including regional therapy to the liver, but larger studies are necessary. FDG PET imaging appears helpful to differentiate malignant from benign hepatic lesions, with the exception of false negative HCC, false negative infiltrating cholangiocarcinoma, and false positive inflammatory lesions. It is not helpful to identify HCC in patients with cirrhosis and regenerating nodules. In patients with hepatic primary malignant tumors trapping FDG, FDG PET imaging does identify unexpected distant metastases (although military carcinomatosis is often false negative) and can help in monitoring therapy. FDG PET imaging is especially helpful for the pre-operative diagnosis of pancreatic carcinoma in patients with suspected pancreatic cancer in whom CT fails to identify a discrete tumor mass or in whom FNAs are non-diagnostic. By providing preoperative documentation of pancreatic malignancy in these patients, laparotomy may be undertaken with a curative intent, and the risk of aborting resection due to diagnostic uncertainty is minimized. FDG PET imaging is also useful for M staging and restaging by detecting CT-occult metastatic disease, and allowing non-therapeutic resection to be avoided altogether in this group of patients. As is true with other neoplasms, FDG PET can differentiate post-therapy changes from recurrence and holds promise for monitoring neo-adjuvant chemoradiation therapy. FDG PET imaging is complementary to morphological imaging with CT; therefore, integrated PET/CT imaging provides optimal images for interpretation. The diagnostic implications of integrated PET/CT imaging include improved detection of lesions on both the CT and FDG PET images, better differentiation of physiologic from pathologic foci of metabolism, and better localization of the pathologic foci. This new powerful technology provides more accurate interpretation of both CT and FDG PET images and therefore more optimal patient care. PET/CT fusion images affect the clinical management by guiding further procedures (biopsy, surgery, radiation therapy), excluding the need for additional procedures, and changing both inter- and intra-modality therapy.