MicroRNA profiling for the identification of cancers with unknown primary tissue-of-origin

Cancer of unknown primary (CUP) represents a common and important clinical problem. There is evidence that most CUPs are metastases of carcinomas whose primary site cannot be recognized. Driven by the hypothesis that the knowledge of primary cancer could improve patient's prognosis, we investigated microRNA expression profiling as a tool for identifying the tissue of origin of metastases. We assessed microRNA expression from 101 formalin-fixed, paraffin-embedded (FFPE) samples from primary cancers and metastasis samples by using a microarray platform. Forty samples representing ten different cancer types were used for defining a cancer-type-specific microRNA signature, which was used for predicting primary sites of metastatic cancers. A 47-miRNA signature was identified and used to estimate tissue-of-origin probabilities for each sample. Overall, accuracy reached 100% for primary cancers and 78% for metastases in our cohort of samples. When the signature was applied to an independent published dataset of 170 samples, accuracy remained high: correct prediction was found within the first two options in 86% of the metastasis cases (first prediction was correct in 68% of cases). This signature was also applied to predict 16 CUPs. In this group, first predictions exhibited probabilities higher than 90% in most of the cases. These results establish that FFPE samples can be used to reveal the tissue of origin of metastatic cancers by using microRNA expression profiling and suggest that the approach, if applied, could provide strong indications for CUPs, whose correct diagnosis is presently undefined.

Molecular testing of solid tumors

CONTEXT

Molecular testing of solid tumors is steadily becoming a vital component of the contemporary anatomic pathologist's armamentarium. These sensitive and specific ancillary tools are useful for confirming ambiguous diagnoses suspected by light microscopy and for guiding therapeutic decisions, assessing prognosis, and monitoring patients for residual neoplastic disease after therapy.

OBJECTIVE

To review current molecular biomarkers and tumor-specific assays most useful in solid tumor testing, specifically of breast, colon, lung, thyroid, and soft tissue tumors, malignant melanoma, and tumors of unknown origin. A few upcoming molecular diagnostic assays that may become standard of care in the near future will also be discussed.

DATA SOURCES

Original research articles, review articles, and the authors' personal practice experience.

CONCLUSIONS

Molecular testing in anatomic pathology is firmly established and will continue to gain ground as the need for more specific diagnoses and new targeted therapies evolve. Knowledge of the more common and clinically relevant molecular tests available for solid tumor diagnosis and management, and their indications and limitations, is necessary if anatomic pathologists are to optimally use these tests and act as consultants for fellow clinicians directly involved in patient care.

Diagnosis of metastatic neoplasms: molecular approaches for identification of tissue of origin

CONTEXT

Tumors of uncertain or unknown origin are estimated to constitute 3% to 5% of all metastatic cancer cases. Patients with these types of tumors show worse outcomes when compared to patients in which a primary tumor is identified. New molecular tests that identify molecular signatures of a tissue of origin have become available.

OBJECTIVE

To review the literature on existing molecular approaches to the diagnosis of metastatic tumors of uncertain origin and discuss the current status and future developments in this area.

DATA SOURCES

Published peer-reviewed literature, available information from medical organizations (National Comprehensive Cancer Network), and other publicly available information from tissue-of-origin test providers and/or manufacturers.

CONCLUSIONS

Molecular tests for tissue-of-origin determination in metastatic tumors are available and have the potential to significantly impact patient management. However, available validation data indicate that not all tests have shown adequate performance characteristics for clinical use. Pathologists and oncologists should carefully evaluate claims for accuracy and clinical utility for tissue-of-origin tests before using test results in patient management. The personalized medicine revolution includes the use of molecular tools for identification/confirmation of the site of origin for metastatic tumors, and in the future, this strategy might also be used to determine specific therapeutic approaches.

Liver metastases from cancer of unknown primary (CUPL): a retrospective analysis of presentation, management and prognosis in 49 patients and systematic review of the literature

AIM

Patients with liver metastases from cancer of unknown primary (CUPL) have a dismal prognosis. We retrospectively analysed their management and outcome and performed a systematic review of CUPL series published in the literature.

PATIENTS AND METHODS

Electronic data from 49 CUPL patients referred to Hellenic Cooperative Oncology Group (HeCOG) centers were retrospectively studied for characteristics of clinical presentation, diagnostic workup, management, outcome and prognostic factors. A systematic literature review was undertaken in PubMed and EmBase databases.

RESULTS

All our patients (males: 31, females: 18; median age: 65) underwent a computed tomography scan (CT) of the abdomen, 71% a thoracic CT, 53% gastroscopy and 47% colonoscopy. The commonest histologic subtypes encountered were adenocarcinoma (N=34) or undifferentiated carcinoma (N=12). The liver was the only metastatic site in 38% of patients, while it was accompanied with other metastatic sites in 62% (the commonest: lung, bone and lymph nodes). Forty-seven patients received first-line chemotherapy (42 platinum based) and 16 second-line. An objective response was observed in six patients (12%), median survival being 10 months (95% CI, 7-13). In univariate analysis, good performance status and normal baseline serum CEA levels were correlated with superior survival, while in multivariate analysis only age<55 (HR 0.16, p=0.02) and the absence of extrahepatic disease (HR 0.21, p=0.007) predicted for a better outcome. Published data from four relevant series (total patients=662) parallel our findings.

CONCLUSIONS

Patients with liver metastases from CUP are resistant to conventional types of treatment and carry a poor prognosis. Understanding the molecular biology of CUP is essential for the development of new, targeted effective therapies.