Clinical value of 18F-FDG PET-CT in detecting primary tumor for patients with carcinoma of unknown primary

Clinical value of 18F-FDG PET-CT in detecting primary tumor for patients with carcinoma of unknown primary: Publication year: 2012


Objective: 
To investigate the clinical value in detecting occult primary tumors with ¹⁸F-FDG PET-CT whole body imaging.

Methods: 
120 patients with unknown primary origin were referred for ¹⁸F-FDG PET-CT whole body imaging. All patients were performed ¹⁸F-FDG PET-CT whole body scan. PET-CT images were interpreted by visual inspection and semi-quantitative analysis (standardized uptake value, SUV). Histopathological and formal clinical follow-up findings were used to assess the value of FDG PET-CT.

Results: 
FDG PET-CT was able to detect the primary tumor in 54/120 patients (42.5%). The primary tumors were confirmed by histopathologic and formal clinical follow-up findings, and located in the head and neck (n =17), the lung (n =19), the breast (n =2), the esophagus (n =1), the stomach (n =2), the bile ducts (n =1), the pancreas (n =3), the co1on (n =3), the ovary (n =2), the prostate (n =l), others (n =3). FDG PET results were proved false positive in 9 patients (7.5%), which were located in the head and neck (n =3), the lung (n =1), the gastric (n =1), the colon (n =2), the ovary (n =1), the prostate (n =l).

During the clinical follow-up of median 32months (range, 2–45months), primary tumor was found in only 5 patients of 60 cases unidentified by PET-CT (breast cancer, gastric cancer, co1on cancer, prostate cancer and urinary tumors, respectively). The sensitivity, specificity, and accuracy of ¹⁸F-FDG PET-CT in the detection of the primary tumor site were 91.5%, 85.2%, and 88.3%, respectively.

Conclusion:
¹⁸F-FDG PET-CT whole body imaging is both a noninvasive and a very sensitive tomographic whole-body imaging modality, allowing for the detection of a primary tumor and complete tumor staging in single examination, which can contribute substantially to selecting appropriate therapeutic methods and evaluating prognosis. Perhaps ¹⁸F-FDG PET-CT whole body imaging should be used as a first-line imaging modality for patients with carcinoma of unknown primary rather than using it after other diagnostic procedures have failed to identify a primary tumor.

Molecular Test Aids in Identifying Cancers of Unknown Origin - Medscape (pathology/molecular diagnostic test - 15 different cancer types...)

".....The identity of most tumors can be determined "with confidence" by clinicians with histologic, clinical, and radiographic findings, say the study authors, led by James P. Grenert, MD, from the Department of Pathology at UCSF. "However, when tumors are poorly differentiated or metastatic with no clear primary, identifying the tissue of origin is difficult," they write.
Immunohistochemical stains may or may not be helpful in identifying the tumor origin. Molecular testing of tumors is an additional means of characterizing these tumors, the authors say.
TOO is the only molecular diagnostic test for cancer tissue of origin cleared by the US Food and Drug Association, the manufacturer notes. It is limited to identifying 15 types of tumor tissues: bladder, breast, colorectal, gastric, testicular germ cell, kidney, hepatocellular, nonsmall-cell lung, non-Hodgkin's lymphoma, melanoma, ovarian, pancreas, prostate, thyroid, and sarcoma. These 15 tumor types represent 90% of all cancers, the company points out....."cont'd

The study was funded in part by a grant from Pathwork Diagnostics.
Clin Chim Acta. 2011;412:1462–1464. Abstract

abstract: Familial Risks in Cancer of Unknown Primary: Tracking the Primary Sites

Conclusion:

The present data show that CUP is not a disease of random metastatic cancers but, instead, a disease of a defined set of cancers. The association of CUP with families of kidney, lung, and colorectal cancers suggests a marked genetic basis and shared metastatic mechanisms by many cancer types. Familial sites shared by CUP generally match those arising in tissue-of-origin determinations and, hence, suggest sites of origin for CUP. Mechanistic exploration of CUP may provide insight into defense against primary tumors and the metastatic process.

abstract: Familial Risks in Cancer of Unknown Primary: Tracking the Primary Sites — JCO