Prospective analysis of pre and postoperative laboratory parameters associated with thrombosis in patients with ovarian cancer

Background Patients with ovarian cancer have a high risk of developing thrombosis. We aimed to investigate laboratory parameters associated with thrombosis including deep vein thrombosis (DVT) and pulmonary thromboembolism in patients treated for ovarian cancer.


Abstract Background
Patients with ovarian cancer have a high risk of developing thrombosis.We aimed to investigate laboratory parameters associated with thrombosis including deep vein thrombosis (DVT) and pulmonary thromboembolism in patients treated for ovarian cancer.

Methods
We collected pre and post operative blood samples from 133 patients undergoing surgery for ovarian cancer at National Cancer Center, Korea between December 2021 and August 2022.The measured parameters were white blood cell (WBC) count, hemoglobin, platelets, monocytes, serum glucose, CA125, D-dimer, brinogen, prothrombin time (PT), activated partial thromboplastin time (aPTT), brinogen degradation products (FDP), antithrombin III, protein C, protein S, plasminogen, plasminogen activator inhibitor 1 (PAI-1), homocysteine, N-terminal pro-brain natriuretic peptide (NT-proBNP), interleukin 6 (IL-6), thrombopoietin (TPO), soluble P-selectin and granulocyte stimulating factor (G-CSF).Body mass index (BMI) of patients were collected.Differences between patients who developed thrombosis and those without were compared with Wilcoxon rank-sum test and we analyzed the continuous variables using logistic regression.

Results
Twenty-one (15.8%) patients developed thrombosis ranging from 6 to 146 days (median 15 days) after surgery.FIGO stage, age and BMI were not signi cantly different among the two groups.Pre operative values of homocysteine (p = 0.033) and IL-6 (p = 0.043) were signi cantly increased and post operative aPTT (p = 0.022) was prolonged and plasminogen (p = 0.041) was decreased in patients with thrombosis.

Conclusions
Pre operative homocysteine, IL-6 and post operative aPTT, plasminogen were associated with thrombosis in ovarian cancer patients.

Background
Venous thromboembolism (VTE) is a major cause of morbidity in cancer patients and ovarian cancer is associated with one of the highest incidence rates of VTE [1].Patients with ovarian cancer have several disease and treatment related features that are recognized as risk factors.The tumor arises within the pelvis and patients undergo abdominopelvic surgery as a part of the de nitive treatment of the disease [2].D-dimer levels are often elevated in ovarian cancer patients [3] and overexpression of tissue factors associated with elevated D-dimer levels is believed to be a factor promoting a hypercoagulable stage in ovarian cancer [4].
Much of the data on various risk factors are confounded by studies that comprise heterogenous patient populations of multiple cancer types with varying disease and treatment associated factors.In this study, we therefore aimed to chart the patients who have undergone surgery for ovarian cancer and evaluate pre and post operative biomarkers that may predict the development of VTE throughout the course of their treatment.

Results
Twenty-one (15.8%) patients developed thrombosis.FIGO (the International Federation of Gynecology and Obstetrics) stage III was most common (54.1%) and high grade serous carcinoma was the most common histology type (74.4%) (Table .1).Patients' age ranged from 24 to 83 years with median age of 57.FIGO stage (p = 0.124), histology type (p = 0.861), BMI (p-0.377) and age (p = 0.961) were not signi cantly different among the two groups.Although FIGO stage was analyzed to be statistically insigni cant, 20 patients (95.2%) among 21 patients with thrombosis were in stage III-IV.
Among the 21 patients, 5 patients developed VTE in splenic vein and 4 of them had splenectomy during the surgery.Pulmonary thromboembolism (PTE) was detected in 4 patients.VTE developed after 6 to 146 days after surgery with median of 15 days.The site and postoperative date of each case are listed in Table .2.Three patients had experienced lymphedema prior to con rmation of thrombosis on imaging studies.
Preoperative values of homocysteine (p = 0.033) and IL-6 (p = 0.043) were signi cantly increased in univariable logistic regression analysis (Table 3).In postoperative setting, aPTT (p = 0.022) was signi cantly prolonged and plasminogen (p = 0.041) was decreased in patients with thrombosis (Table.4).IL-6 was not evaluable in postoperative setting since it was increased beyond quanti able range in all patients after surgery.

Discussion
In this study, we selected the test items from our previous research (paper under review) based on more than three thousand patients in our institute.We included biomarkers associated with coagulation such as PT, aPTT, D-dimer, FDP, brinogen, plasminogen, PAI-1 and natural anticoagulants such as ATIII, protein C and protein S activity.Soluble P-selectin [5], homocysteine [6], NT-proBNP [7] were biomarkers previously published to be related to venous thromboembolism.IL-6, G-CSF and TPO were studied in mouse models to be associated with thrombosis in ovarian cancer [8].
In this study preoperative homocysteine was signi cantly increased in patients with thrombosis.Epidemiologic studies have shown that elevated plasma levels of homocysteine are independently associated with cardiovascular diseases, including venous thromboembolism and atherosclerotic arterial diseases such as myocardial infarction and stoke [9].Homocysteine is a structural intermediate generated during the synthesis of cysteine from methionine and mechanistic studies have shown that homocysteine can exert a variety of effects to promote thrombosis including increased expression of adhesion molecules, cytokines, tissue factor and coagulation factor, inhibition of brinolysis, disruption of nitric oxide metabolism and increased platelet reactivity [6].However, mouse studies have revealed that hyperhomocysteinemia, in itself, is not su cient to promote thrombosis [10].Rather, other factors associated with abnormal homocysteine metabolism may be responsible for the propensity to thrombosis.
Several studies have shown that leukocytosis and thrombocytosis were frequently observed in patients with tumors and it is due to the increased level of IL-6 expressed in the tumor.Our study revealed that the patients with thrombosis had higher level of preoperative IL-6 level.However, WBC and platelets were not signi cantly increased in the thrombosis group.
In our study, postoperative aPTT was signi cantly prolonged in thrombosis group.Prolonged aPTT and normal PT means that the defect lies within the intrinsic coagulation pathway and prolonged aPTT in the setting of thrombosis may re ect the presence of a lupus anticoagulant [11].Although anticoagulants were administered to all patients after the surgery, patients who developed thrombosis showed signi cantly prolonged postoperative aPTT whereas preoperative aPTT level had not shown the difference.Therefore, presence of anticoagulant can be ruled out.Another hypothesis can be that prolonged aPTT which represents bleeding, may have caused rebound hypercoagulable state and caused thrombosis.
Postoperative plasminogen was decreased in thrombosis group.Plasmin is an important enzyme present in blood that degrades many blood plasma proteins including brin clots and is released as a zymogen called plasminogen [12].Plasminogen is necessary for removal of any clots which may start to form thrombosis.There are a few studies evaluating the brinolytic system in cancer-associated thrombosis.One study found that patients with DVT had prolonged clot lysis time compared to healthy controls [13], and a case-control study found that higher levels of active PAI-1 were observed in VTE patients compared with controls [14].Our study showed no difference in PAI-1 but decreased plasminogen level in thrombosis group.
Although the study is done on a limited number of patients, this study consists of a single type of cancer and samples from a consistent time point during the treatment.It is important to nd novel biomarkers for thrombosis, considering that patients had still developed thrombosis despite preventive measures including oral anticoagulants and elastic stockings were applied.Abbreviations: WBC (white blood cell), Hb (hemoglobin), PLT (platelet), PT (prothrombin time), aPTT (activated partial thromboplastin time), FDP ( brinogen degradation products), ATIII (Antithrombin III), PAI-1 (plasminogen activator inhibitor), IL-6 (interleukin 6), TPO (thrombopoietin), G-CSF (Granulocyte colony stimulating factor), N/A (not applicable) Figures

Table . 2
International Federation of Gynecology and Obstetrics), HGSC (High grade serous carcinoma), CA (carcinoma), LGSC (Low grade serous carcinoma), BMI (Body mass index) Site and postoperative date of developed thrombosis