How Cancer Increases the Risk of Pulmonary Embolism

When a person is diagnosed with Pulmonary Embolism is a blockage in a lung artery caused by a blood clot that has traveled from elsewhere in the body, the news can feel like a double blow. Add cancer to the mix, and the risk of that clot forming spikes dramatically. This article breaks down why cancer patients are far more prone to PE, what mechanisms drive the connection, and how doctors and patients can spot and manage the danger early.

Why Cancer Makes Blood Clots More Likely

At its core, cancer creates a hyper‑coagulable state-meaning the blood is primed to clot. Several factors contribute:

• Tumor‑derived tissue factor: Many tumors release tissue factor, a protein that kick‑starts the clotting cascade.
• Inflammation: Cytokines such as IL‑6 increase platelet activation.
• Compression of veins: Large abdominal tumors can press on pelvic veins, slowing blood flow.
• Immobility: Hospital stays, surgery, and fatigue keep patients in bed longer.
• Treatment‑related effects: Chemotherapy and radiation can damage vessel walls and alter clotting factors.

All of these fall under the umbrella term hypercoagulability, a hallmark of what clinicians call cancer‑associated thrombosis.

From Deep Vein Thrombosis to Pulmonary Embolism

Most PEs start as a deep vein thrombosis (DVT) in the legs or pelvis. When a clot breaks loose, it travels through the venous system, reaches the right heart, and is pumped into the lungs. This cascade is known as venous thromboembolism (VTE), the broader category that includes both DVT and PE.

In cancer patients, the incidence of VTE can be as high as 20% in the first six months after diagnosis, compared with less than 1% in the general population.

Incidence of Pulmonary Embolism by Cancer Type

These numbers come from large registry studies up to 2024 and highlight that not all cancers carry the same risk. Pancreatic and lung cancers top the list, so clinicians keep a closer eye on those patients.

Clinical Signs That Should Raise Alarm

PE can be silent, but when symptoms appear they often mimic other illnesses, making diagnosis tricky. In a cancer setting, watch for:

1. Sudden shortness of breath that worsens at rest.
2. Sharp chest pain that intensifies with deep breathing.
3. Rapid heart rate (tachycardia) without fever.
4. Unexplained drop in blood oxygen saturation.
5. Swelling or pain in a leg-possible DVT precursor.

Because cancer patients may already experience fatigue or dyspnoea from tumour burden, clinicians often rely on biomarkers like D‑dimer and imaging (CT pulmonary angiography) to confirm PE.

Managing the Double Threat: Anticoagulation Strategies

Once PE is confirmed, the mainstay of treatment is anticoagulation. However, cancer patients pose a dilemma: they need strong clot prevention but also have higher bleeding risks, especially after surgery or during thrombocytopenia from chemotherapy.

Current guidelines recommend low‑molecular‑weight heparin (LMWH) as first‑line, but direct oral anticoagulants (DOACs) like apixaban are gaining traction for their oral convenience. The choice hinges on:

• Kidney function (creatinine clearance).
• Drug‑drug interactions with chemotherapy agents.
• Platelet count (keep >50×10⁹/L when possible).
• Location of tumour (gastrointestinal tumours have higher bleeding risk with DOACs).

In high‑risk scenarios, temporary placement of an inferior vena cava (IVC) filter may be considered, but filters carry their own complications and are not a long‑term solution.

Prevention: Reducing the Chance of PE Before It Happens

Prevention strategies are layered:

1. Risk assessment tools such as the Khorana score help identify patients who need prophylactic anticoagulation.
2. Mechanical methods like graduated compression stockings or intermittent pneumatic compression for bedridden patients.
3. Pharmacologic prophylaxis - low‑dose LMWH or low‑dose DOACs during high‑risk periods (e.g., after major surgery).
4. Lifestyle tweaks - encouraging ambulation, hydration, and smoking cessation.

Studies published through 2023 show that appropriate prophylaxis can cut VTE rates by up to 50% in high‑risk cancer cohorts.

Key Take‑aways for Patients and Caregivers

• Know that cancer itself makes blood more clot‑prone - it’s not just the treatment.
• If you experience sudden breathlessness or chest pain, seek medical help right away.
• Ask your oncologist about a VTE risk assessment; a simple questionnaire could change your medication plan.
• Follow any prescribed anticoagulation regimen exactly; missing doses can be as dangerous as bleeding.
• Stay active, stay hydrated, and keep track of any leg swelling.

Understanding the link between cancer and pulmonary embolism empowers you to catch warning signs early and work with your care team on a safe prevention plan.

Frequently Asked Questions

Why does cancer increase the risk of blood clots?

Tumours release proteins like tissue factor, trigger inflammation, and can compress veins. Combined with immobility and chemotherapy‑induced vessel damage, these factors create a hypercoagulable environment that makes clots more likely.

What symptoms should a cancer patient watch for that could signal a PE?

Sudden shortness of breath, sharp chest pain that worsens with breathing, rapid heartbeat, unexplained low oxygen levels, and swelling or pain in a leg are the most common red flags.

Is anticoagulation safe for patients undergoing chemotherapy?

Generally yes, but dosage and drug choice must consider kidney function, platelet counts, and interactions with chemotherapeutic agents. Low‑molecular‑weight heparin is often preferred, though DOACs are an option for many patients.

How does the Khorana score help prevent PE?

The Khorana score assigns points based on cancer type, blood counts, and body mass index. A score of 2 or higher flags patients who benefit from prophylactic anticoagulation, reducing their VTE risk.

Can lifestyle changes lower the risk of PE in cancer patients?

Yes. Regular ambulation, adequate hydration, avoiding prolonged immobility, and quitting smoking all help keep blood flowing and reduce clot formation.