Abstract Introduction Owing to increasing numbers of heart failure patients a search for new biomarkers predicting prognosis is desirable. Background The purpose of this study was to analyze levels of cancer biomarkers in patients with severe heart failure before or after left ventricular assist device (LVAD) implantation and estimate its impact on survival during LVAD support. Methods We retrospectively analyzed data of all consecutive 168 LVAD recipients (92.8%- male, mean age 53.3 years ( median - 56.6, SD 12.0 ), median INTERMACS profile- 3.0, ischemic etiology of heart failure- 52.4%, 41.0% post CRT-D and 54.8% post ICD implantation, 36.9 post IABP, 5.4% post ECMO%, 11.9% post CABG and 8.9% post other cardiac surgery before LVAD implantation) implanted with continuous-flow LVAD (59.5%-HeartMate3, 35.1%- HeartWare, 5.4%-Heart Mate II) in our institution within years 2009-2023. Among comorbidities 63% of patients had atrial fibrillation or flutter, 41.6%- diabetes, 37.5%- arterial hypertension, 48.8%-renal failure, 7.1% pulmonary obstructive disease, 56.5% had pulmonary hypertension with mean pulmonary artery pressure above 25 mm Hg in right heart catheterization and 47% of patients had a history of cardiac arrest or sustained ventricular arrythmia before LVAD implantation. The overall mortality was 44.0 %. 31% patients were transplanted during LVAD support and in 4 patients (2.3%) LVAD was explanted or deactivated. Patient were followed to death, heart transplantation, LVAD explantation or the end of observation in our institution. Mean time of LVAD support was 885 days (1-2570). 23% of patients had right ventricular failure (RVF) early post LVAD implantation while 7.7% had late form of RVF. Results Serum concentrations of cancer biomarkers: carcinoembryonic antigen (CEA), carbohydrate antigen (CA)19-9, carbohydrate antigen(CA)-125 and alpha fetoprotein (AFP) taken before (56 patients -33.3%) or after (24 patients-14.3%) LVAD implantation were analyzed. Mean values, rate of abnormal results and correlation of abnormal results of CEA, CA19-9, CA-125, AFP with mortality during LVAD support were depicted in Table 1. No statistically significant correlations were found between levels of abovementioned cancer biomarkers and mortality though a trend towards increased mortality could be observed for abnormal results of CEA and Ca 19-9 taken before LVAD implantation. No malignant neoplasms were found in all analyzed patients except of one in whom a recurrence of lymphoma was found 2 months after LVAD implantation. Conclusions Patients with severe heart failure before and after LVAD implantation may present abnormal values of cancer biomarkers despite no found neoplasms. Our observation suggests that elevated cancer biomarker levels could predict mortality in heart failure patients after LVAD implantation. Further research is needed to confirm this thesis and investigate mechanisms of this phenomenon.