Introduction
A thromboembolic event may be the first symptom of cancer.[
1,
2] The first data on such a relationship concerned pulmonary embolism and deep vein thrombosis.[
3] Another correlation was found for stroke.[
4,
5,
6] The effects of cancer screening programs in patients after pulmonary embolism have been analyzed.[
7] Cancer screening programs for stroke patients have also been planned.[
8] We need data on the importance of myocardium infarction as the first symptom of cancer.[
9]
It seems that there is a high risk of thromboembolism in the group of blood cancers, where coagulation disorders may be particularly turbulent.[
10] However, initiating anticancer therapy may be associated with increased activation of prothrombotic factors or damage to the vascular endothelium, consequently leading to coagulopathy. An exceptionally high risk of venous and arterial thromboembolic events (VTE/ATE) is associated with the use of antiangiogenic drugs, second- and third-generation BCR-ABL inhibitors and immune checkpoint inhibitors.[
11,
12,
13,
14] These observations allowed us to define a separate group of complications related to oncological treatment called vascular toxicity.[
15] It includes symptomatic and asymptomatic venous and arterial thrombosis, myocardial infarction, stroke, peripheral artery diseases, and coronary artery spasms.
Both venous and arterial thromboembolic events are associated with worse prognosis in cancer patients.[
16,
17] It seems clinically essential to assess to what extent a given event is related to the cancer and to what extent it is related to its treatment. Identification of factors predisposing to the occurrence of venous and arterial thromboembolic events and the time relationship to the moment of cancer diagnosis seems to be crucial to optimize recommendations for primary and secondary prevention. This is especially important because these patients are at an exceptionally high risk of bleeding, which results from thrombocytopenia, platelet dysfunction, and bone marrow suppression.[
18,
19] Moreover, knowing such a temporal relationship may help plan optimal oncological screening. This is particularly important in patients with blood cancers because we have the most minor epidemiological data.
The aim of the study was to assess the time relationship between the moment of diagnosis of hematological cancer and the moment of occurrence of venous or arterial thromboembolism. The second aim was to identify VTE/ATE risk factors related to the type of cancer and cardiac characteristics of the patients.
Results
At the Institute of Hematology and Transfusion Medicine in Warsaw, from March 2021 through March 2023 (two years), 1283 hemato-oncology patients underwent cardio-oncology evaluation. The majority were men (673/52.5%), the median age was 63 years (IQ: 47 - 71) (
Table 1,
Figure 1)
The dominant hematological diagnoses were acute myeloid leukemia (n= 270, 21%), non-Hodgkin's lymphoma (NHL) (n= 250, 19.5%), and multiple myeloma (n= 223, 17.4%), chronic lymphocytic leukemia (CLL) (n=101, 7.88%), acute lymphocytic leukemia (ALL) (n=76, 5.92%). Nearly half of the patients had at least one comorbid cardiovascular disease, of which arterial hypertension (40%) and cardiac arrhythmias (15.8%) were predominant.
The group of 101 (7.8%) patients with a history of thromboembolism (TE) were identified in the analyzed population. Venous thromboembolic events (VTE) accounted for 53%. It was shown that VTE episodes occurred significantly more often after the initiation of anticancer treatment (p< 0.0001) compared to arterial thromboembolism (ATE), most of which were observed before (70.2%) the hematological malignancy was revealed.
The time-dependence analysis showed that the highest risk of diagnosing acute VTE occurs in the first months after anticancer treatment is started (
Figure 2). A similarly strong correlation was not demonstrated in the case of arterial events, which were observed mainly before the diagnosis of hematologic cancer and thus before the initiation of anticancer treatment - 33 cases, representing 70.2% of all diagnoses of arterial thromboembolic complications (
Figure 3).
Through an analysis of the distribution of thromboembolic events in relation to histopathological diagnoses of hematological malignancies, it was shown that VTE was most often diagnosed in patients with AML (17 cases/6.30%/p=0.055), ALL (7 cases/9.21%/p=0.025) and chronic myeloproliferative disease (7 cases/14.58%/p=0.0003). However, there was no increased incidence of ATE depending on the diagnosis of hematologic cancer (
Table 2).
For the occurrence of ATE events before the diagnosis of hematologic cancer, the cardiac history was important, both in terms of the presence of classic risk factors for atherosclerosis, i.e., older age and hypertension and as co-occurring heart failure, coronary artery disease, or arrhythmia (
Table 3). Interestingly, all these factors were significant only before the diagnosis of cancer; their significance disappeared after the diagnosis of cancer and the initiation of hematological treatment. Only coronary artery disease retained its importance for the risk of ATE after a cancer diagnosis.
Cardiological history was of no significance in the context of VTE. (
Table 4). Only diabetes melittus had the significant correlation with the diagnosis of VTE especially after diagnosis of hematological malignancy (OR=2.42, p=0.03). Some histopathological diagnoses were also important for VTE. Diagnosis of acute lymphocytic leukemia correlated with later with increased probability of VTE (OR=3.05, p=0.015). In the case of myeloproliferative disease, the risk of VTE was increased both before and after diagnosis (OR=6.79, p=0.004 and OR=3.12, p=0.04.
Discussion
Venous and arterial thromboembolic events (VTE/ATE) occur with quite significant frequency in hematological patients. The latest data indicate that the pathogenesis and clinical picture may differ from solid tumors.[
20] Regardless of the cause or type of tumor, the prognosis of patients with a thrombotic event is always poorer.[
16,
21] The mortality risk is particularly high when cancer is diagnosed at the same time as a thromboembolic event. The benefits of anticoagulant therapy using anticoagulants that are not vitamin K antagonists may also differ in hemato-oncology, and there is undoubtedly less evidence for its effectiveness.[
22] There may be a greater risk of complications such as bleeding, which may be caused by thrombocytopenia and platelet dysfunction.[
23] The risk of late complications such as thromboembolic pulmonary hypertension may also be higher.[
24] Myeloproliferative diseases are a known risk factor for the development of pulmonary hypertension.[
25] Risk factors for the development of pulmonary hypertension in the course of myeloproliferative diseases are constantly discussed.[
26] Our publication shows an increased risk of venous thromboembolic complications, adding a new aspect related to thromboembolic changes. Currently, pulmonary hypertension due to myeloproliferative diseases is classified in group 5, i.e. with unknown or multifactorial pathogenesis.[
27]
Multiple myeloma has well-defined indications for primary thromboprophylaxis.[
28,
29] This is due to the high risk of thromboembolic events associated with the use of immunomodulatory drugs, steroids, or the presence of fractures and immobilization.[
30] Lymphoma patients also usually receive primary antithrombotic prophylaxis because, according to the thromboembolic risk stratification proposed by Khorana, lymphoma receives one point.[
31] Such prophylaxis can be considered from two points of view, according to the latest research.[
32,
33] For this reason, perhaps in our population, patients with myeloma and non-Hodgkin's lymphoma did not experience VTE very often.
Our data, however, confirm other reports indicating that patients with AML and ALL are at risk of VTE.[
14]Our analysis shows that patients with AML and ALL are at exceptionally high risk of VTE events. In the literature, the incidence of VTE in AML is estimated to range from 2% to nearly 15%; in our population 6.3% of patients with AML experience an acute episode of VTE.[
34] The pathogenesis of these events is complex, but considering the correlation with the initiation of chemotherapy, it should be assumed that the dominant mechanism is the massive release of procoagulants due to the lysis of cancer cells.[
35] This mechanism is strengthened by hemodynamic changes and vascular damage. Another factor of thrombotic events in AML is DIC (disseminated intravascular coagulation), which occurs in about 30% of patients at diagnosis.[
36] The coexistence of increased risk of thrombosis and bleeding, such as thrombocytopenia typical of AML, makes it challenging to choose the optimal antithrombotic therapy. It should be emphasized that, unlike patients with lymphoma and ALL, a VTE episode in patients with AML is not associated with an increased risk of death within one year.[
37,
38]. Our study confirmed the problem of VTE in AML is noticeable, although the result of the correlation between VTE and AML was on the verge of statistical significance.
Another group of our patients at a clear significant risk of VTE is patients with ALL, with an incidence of 9.2%. In a large meta-analysis of 72 prospective studies, including 9061 patients, the VTE incidence rate (IR) in ALL was determined to be 5% (95% CI: 4–6%).[
32] The authors emphasize that antithrombotic prophylaxis using LMWH significantly reduces the risk of VTE events in this group. One of the main factors associated with a higher rate of thrombotic events is the use of chemotherapy.[
39] There are no similar observations in the case of targeted treatment with TKIs (tyrosine kinase inhibitors), and reports regarding the use of steroids are unclear.[
39,
40,
41]. Our study clearly shows that after the diagnosis of ALL, and therefore during active treatment of ALL, we had a problem with a significantly higher incidence of VTE. Therefore, future studies should be conducted to identify risk factors for VTE in ALL related not so much to the patients' characteristics but to the drugs used for ALL treatment and the possible degree of aggressiveness of the ALL course.
It should be added that it is surprising that patients with AML and ALL were not included in large clinical trials with new anticoagulants.[
42,
43] The latest guidelines of the European Society of Cardiology emphasize this fact.[
44] This may be surprising in the context of the results of our observation and the cited studies. These patients are disqualified from large clinical trials due to thrombocytopenia and a high baseline risk of bleeding. Therefore, personalized trials should be planned for AML and ALL patients in terms of both primary and secondary prevention of VTE.
A lot of data show that the risk of both venous and arterial thromboembolic events is the highest during the period of diagnosis of cancer.[
45,
46] The disease in the metastatic phase poses a significantly higher risk of both venous and arterial complications, but this applies to solid tumors.[
14,
47] Also, recurrence of venous thromboembolism is more common in metastatic disease.[
48] Additionally, the molecular type of cancer increases the risk of thromboembolism.[
49] The type of anticancer therapy or supportive care is also important.[
50,
51].
In hematology, of course, we cannot talk about metastatic disease, but we can use other criteria to assess the advancement or aggressive course of a hematological cancer. It is worth checking to what extent VTE diagnosed, especially in ALL and myeloproliferative diseases, is associated with a negative cardiological and oncological prognosis. Our observation shows one more problem. ATE may be a clinical indicator preceding the diagnosis of hematologic cancer by up to several months. This correlation shown in
Figure 3 should attract the attention of interventional cardiologists, who should monitor especially older patients after an ATE episode for a possible subsequent diagnosis of hematologic malignancy.
Our publication is the first to comprehensively analyze the problem of venous and arterial thromboembolic events in patients with hematological malignancies. We have proven that the type of histopathological diagnosis is essential for the risk of venous thromboembolic events (VTE). Many guideline documents indicate that one should remember patient-related factors among the risk factors for thromboembolic complications and those related to cancer and cancer treatment. This, of course, includes the issue of comorbidities that may additionally increase the risk of thromboembolism. Our study shows that coexisting cardiac diseases are not crucial for the occurrence of VTE. This suggests that the main predictors of a VTE are the onco-hematological disease and/or its treatment.[
17,
52] Still, they are decisive for the occurrence of arterial complications, especially before the diagnosis of cancer. Only coronary artery disease remains a significant risk factor for ATE if hematological cancer is already diagnosed and treated. Moreover, in the aspect of hematological malignancies, only ATEs may precede the diagnosis of cancer. Some studies have shown an increased risk of ATE in the period preceding the diagnosis of cancer, suggesting that cancer is associated with a risk of ATE that goes beyond conventional cardiovascular risk factors. Further population studies are needed to determine whether patients with a history of ATE should be screened for hematological malignancies.
To some extent, our study constitutes another step in the discussion about the importance of the so-called "reverse cardio-oncology".[
53,
54] This is a relatively new hypothesis claiming that cardiovascular diseases contribute to the development and progression of cancer.[
55] Of course, the common denominator may be common risk factors, chronic inflammation, and tissue hypoxia in patients with atherosclerosis.[
56,
57] Several preclinical studies are being conducted to elucidate possible pathomechanisms.[
58] Our study may complement the current discussion on the co-occurrence of heart diseases and cancer.[
59] We have proven that ATEs occur quite frequently before the diagnosis of a hematologic malignancy. We do not know whether this is just an early effect of clotting disorders caused by developing blood cancer.
Our study is limited in that it is not a large population study but only an observational study based on cardio-oncologists' activities at the main hematology Polish center. However, given that the current guidelines on cardio-oncology published in 2022 by the European Society of Cardiology in cooperation with the European Hematology Association, recommend risk stratification according to Heart Failure Association -International Cardio-Oncology Society (HFA-ICOS) tool in patients before anticancer treatment, it can be assumed that we analyzed a representative population of patients with hematologic malignancies in the reference Polish hematology center.[
60] Undoubtedly, large population studies are necessary to confirm our observations.