Circulating Tumor Cells, Circulating Tumor DNA and Other Blood-based Prognostic Scores in Pancreatic Ductal Adenocarcinoma - Mini-Review.

Pancreatic ductal adenocarcinoma represents a disease with increasing incidence. Its prognosis is the worst among all malignancies despite the aggressive combined multimodal treatment across all stages. In metastatic disease, median survival is approximatelly one year. The mainstay of treatment is chemotherapy (neo/adjuvant, palliative) and in selected subgroups of patients even radiotherapy. Nevertheless, nowadays there are very few prognostic and/or predictive biomarkers available that can be used to identify and better stratify patients based on risk to tailored treatment. Potentially, promising areas of research are circulating tumor cells and circulating tumor DNA, which can be easily obtained from peripheral blood - so called liquid biopsy. They may serve as a tool to assess response to applied treatment, and to detect the emergence of treatment-resistant clones or early disease relapse. Moreover, their study may allow identification of potentially tumor-specific alterations, which may serve as target structures for targeted (tailored) therapy. Alternatively, different prognostic indexes/scores calculated by analysis of selected parameters of blood and/or biochemistry can be used to better stratify patients based on risk and better predict prognosis. The aim of this mini-review is to provide a basic overview of the current state of the art in this area and its potential significance for clinical practice.

The current role of radiotherapy and systemic therapy in the multidisciplinary treatment of cholangiocarcinoma.

Cholangiocarcinoma is a cancer with very poor prognosis. The only potentially curative approach is surgical resection of tumor. However, the rate of local and distant recurrence after radical surgery is still high. Benefit of adjuvant therapy is not clearly defined, nevertheless patients at high risk of recurrence are indicated to chemotherapy or chemoradiotherapy. Locally advanced, unresectable disease can also be treated with chemotherapy alone, or with her combination with radiotherapy. Required radiation doses are relatively high, therefore it is necessary to use highly conformal radiation therapy. Treatment of metastatic disease is currently based on systemic therapy, combination of gemcitabine and cisplatin as standard of care. Benefit of targeted molecular therapy is not clear at present, but ongoing research in genetic profiling of tumor may help to improve current clinical practice. Patients with cholangiocarcinoma have to be discussed during multidisciplinary team meetings.

Essentials of circulating tumor cells for clinical research and practice.

The major cause of death due to cancer is its metastatic deposit in numerous tissues and organs. The metastatic process requires the migration of malignant cells from primary sites to distant environments. Even for tumors initially spreading through lymphatic vessels, hematogenous transport is the most common metastatic pathway. The detachment of cancer cells from a primary tumor into the blood stream is called epithelial-mesenchymal transition (EMT). As these cells circulate further in the bloodstream they are known as circulating tumor cells (CTCs). The CTC population is highly resilient, enabling the cells to colonize a foreign microenvironment. Alternatively, cancer stem cells (CSCs) may arise from differentiated cancer cells through EMT and an embryonic transdifferentiation process. The presence of CTCs/CSCs in blood seems to be a determining factor of metastasis. This paper reviews various methods of clinical cancer detection as well as the biology and molecular characterization of CTCs/CSCs. Our goal was to summarize clinical studies which used CTC/CSCs for prognosis in patients with breast, colorectal, prostate, lung, ovarian, and bladder cancer.