Pulmonary Embolism and Blood Cancer
Pulmonary embolism is generally caused by blood clots that block the arteries going to the lungs. Symptoms vary a great deal based on the size of the blockage and the involvement of the lung.
Common signs include:
- Shortness of breath;
- Chest pain;
- Pain while eating, bending, scooping, or coughing;
- Pain while at rest, worsening during physical activity;
- Bloody mucus.
Additional symptoms may include:
- Leg pain or swelling;
- Rapid or irregular heartbeat;
- Clammy skin or blue-tinged skin;
How does a Pulmonary Embolism work?
Typically, a pulmonary embolism occurs when a blood clot is pumped out of the heart and into the lungs, through the pulmonary artery. This is the artery that brings blood to the lungs. A clot can be small enough to go unnoticed, but a big one can be life-threatening: it can get stuck in along the artery, and completely block a vessel.
To diagnose pulmonary emboli, a doctor may conduct:
- A ventilation-perfusion scan;
- A high-resolution CT scan;
- A pulmonary angiogram.
Small clots and non-severe symptoms may be treated with blood thinners. Large, severe clots may require clot-busting medication.
Risk in Cancer Patients
Venous thromboembolism (VTE) is the general condition by which a person develops blood clots in their veins. PEs are only one of many consequences of it. Another one is deep vein thrombosis (DVT), when blood clots form in the deep veins, most typically in the legs.
Both VTE and PE are more common in cancer patients, who are about four times as likely to develop venous thromboembolism, pulmonary embolism, and deep vein thrombosis than the general population.
In patients with DVT, part of a clot may break off and travel to the heart and lungs. This will cause PE. However, patients may be affected by PE without having a DVT.
Why do blood clots form in the deep veins?
Reasons may include:
- Vein injuries;
- Damage to a vein’s inner lining;
- Serious injuries;
- Some immune responses;
- Inherited conditions (ex: factor V Leiden);
- Conditions that make the blood thicker;
- Birth control pills;
- Hormone therapy;
- Prolonged bed rest and long flights.
Cancer outpatients at low risk for VTE are advised against clot-preventing medication.
On the contrary, this is recommended to:
- Patients at high risk of VTE;
- Patients with myeloma;
- Patients receiving immunomodulators.
Patients generally receive low-molecular-weight heparin (LMWH) as treatment. Oral blood thinners exist too, but evidence of their efficacy is limited.
A recent study showed that most cancer patients selected oral treatment as opposed to LMWH, which requires injection. However, according to experts, the interplay between the treatment, with underlying comorbidities, should be carefully considered before switching to the oral agent.
PE and VTE in Patients with Blood Cancers
According to early studies, blood cancers (e.g. leukemia, lymphoma, and myeloma) were generally less likely to increase the risk of blood clots than solid tumors (e.g. breast cancer and lung cancer).
However more recent studies counter this theory: the specific type of blood cancer and individual patient characteristics may be playing the key roles in increasing this risk.
Elderly Patients with Chronic Myeloid Leukemia (CML)
According to a 2016 study, elderly patients with Chronic Myeloid Leukemia (CML) present greater percentages of PE than patients without cancer.
It is worth noticing that the percentage of clotting problems did not increase in the patients taking tyrosine kinase inhibitors.
This suggests that underlying factors associated with cancer, rather than the treatment, drove the risk in these CML patients.
Acute Lymphoblastic Leukemia and VTE in Children
While acute lymphoblastic Leukemia (ALL) is a curable malignancy, especially in children, it is also associated with higher risks of VTE.
Pulmonary emboli are not common in children. However, leukemia and other malignancies can heighten the risk of childhood VTE and PE.
The main risk factors for VTE and PE include:
- A central venous catheter;
2.1–16% of children with cancer contract VTE, while 2.6 to 36.7% of patients report catheter-related VTE.
According to a meta-analysis of children affected by leukemia, VTE was reported in 5.2% of children with Acute Lymphocytic Leukemia (ALL), the most common pediatric malignancy. However, reported rates ranged from 1 to 36%.
Acute Promyelocytic Leukemia
Blood clots are less common than bleeding in patients with acute promyelocytic leukemia, a rare type of AML.
This type of blood cancer affects the body’s coagulation system, which often leads to bleeding. Nosebleeds that won’t stop, or a cut that won’t stop oozing are common in these patients.
However, blood clots may still occur. Acute promyelocytic leukemia patients may experience calf swelling due to DVT, or chest pain and shortness of breath caused by PE.
Clotting Risk in Leukemia and Lymphoma
All types of cancer can increase the risk of VTE, according to a 2015 study. Depending on cancer categories, the extent of the risk may vary.
This study saw the lowest risk of VTE was with head and neck cancers, and the highest risk with brain cancer. Leukemia patients presented intermediate risk.
A particular increase in VTE risk is associated with the following cancer types:
- Brain cancer;
- Pancreatic cancer;
- Digestive cancers (e.g. esophagus, gallbladder, bile system, small intestine).
Finally, while cancer patients may be at greater risk of pulmonary embolism, the overall chances of developing a pulmonary embolism are still relatively low. The use of central venous catheters can be life-saving for cancer patients, though it may increase the risk of VTE and PE.