Analysis of Free Cancer and Immune Cells Burden in Peritoneal Fluid of Various Malignancies

Dear Colleagues,

Peritoneal dissemination is a common cause of relapse in many gastrointestinal and gynecological malignancies, and it is related to poor prognosis. It is considered that peritoneal spread is most likely caused by the free cancer cells (FCC), which are exfoliated from primary tumor or involved lymph nodes. According to the TNM classification, the presence of FCC in peritoneal fluid is considered distant metastasis (CY1) and qualifies as stage IV metastatic (M1) disease. Patients with positive peritoneal cytology alone have similar survival to patients with overt peritoneal metastasis. The FCC are able to implant into the peritoneal surface and metastasize.

The presence of FCC in peritoneal fluid has been used as a prognostic and predictive factor of peritoneal recurrence and overall survival. Moreover, some patients undergoing surgery with curative intent will develop peritoneal spread, which is associated with poor outcome. Conventional cytology has low sensitivity and is largely dependent on the institution as well as the pathologist. Immunohistochemistry (IHC) may help to increase the detection rate of the FCC. Molecular diagnostics using RT-PCR used to detect FCC in peritoneal fluid has the advantage of high sensitivity.

Since objective assessment of peritoneal lavage or fluid for FCC is essential for clinical decision making in many cancer patients, it is important to develop a quantitative and reproducible method for such evaluation.

Although various molecules expressed by cancer cells have been implicated in the process of peritoneal dissemination, the influence of immunologic factors is poorly understood. The exhausted T cells in the tumor microenvironment show overexpressed inhibitory receptors and decreased effector cytokine production and cytolytic activity, leading to the failure of cancer elimination and promoting metastasis.

It is our hope that the papers included in this Special Issue will be helpful in providing an overview of the field and in advancing new knowledge in basic and clinical aspects of free cancer and immune cells burden in peritoneal fluid of various malignancies.

Prof. Dr. Wojciech Polkowski
Prof. Dr. Ewelina Grywalska
Guest Editors

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• Peritoneal cytology
• Free cancer cells
• T cell exhaustion
• Circulating immune cells