Background: Ovarian cancer (OC) has the greatest mortality rate among oncogynecological diseases. Most cases are diagnosed at the peritoneal dissemination stage, resulting in radical treatment. Most cases (75%) are diagnosed in III-IV stages at the stage of peritoneal dissemination, making the radical treatment impossible. Intraoperative hyperthermic intraperitoneal chemoperfusion (HIPEC), which has ceased to be an experimental technique over the past decade, is increasingly used among the methods of combating peritoneal carcinomatosis and demonstrates an increase in recurrence-free and overall survival in advanced stages of OC. Nevertheless, certain pathophysiological aspects of the effect of HIPEC on intra-abdominal homeostasis, and therefore on the further course of the disease, have not been elucidated. However, understanding this effect may be the key to the successful application of HIPEC and predicting its efficacy in each case of OC.
 Objectives: To access changes in intraperitoneal homeostasis in patients with advanced OC after HIPEC procedure (as a stage of cytoreductive surgery); in particular, to evaluate changes of TNF and TGF-β expression under the influence of HIPEC and systemic chemotherapy in the OC microenvironment.
 Materials and methods: The study included 33 OC patients treated at Lviv Regional Cancer Centre in 2016–2020. Twelve of them received HIPEC. The primary tumor cultures and primary cultures of peritoneal mesothelium and macrophages were obtained for all patients. The cytokines TNF and TGF-β activity were determined in their conditional media.
 Results: The decrease of TNF and TGF-β concentrations in the drainage exudate after HIPEC was revealed compared with the same parameters in the ascitic fluid before the operation. One-hour hyperthermia of the primary culture of peritoneal ascites-associated macrophages of recurrent OC patients decreased the TNF level in conditional media. A decline was found in 10 out of 12 cases.
 Conclusions: HIPEC has a cytokine-modulating effect on the intra-abdominal homeostasis of patients with OC, suppressing TNF expression by peritoneal macrophages. Reduced activity of TNF in supernatants of OC primary tumor cultures was associated with higher sensitivity to chemotherapy.
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