Medical Oncologist
Vascular side effects
Blood Clots and Stroke Risk — on Targeted Therapy
Some targeted therapies raise the risk of blood clots in the veins or arteries. This is a real and monitored risk — and knowing the warning signs is what makes it manageable.
Medically reviewed by Dr. Bharati Devi Gorantla, Medical Oncologist, MBBS · MD · DM (Adyar, Chennai) · ECMO · MRCP SCE (UK) · Last reviewed August 2026
- A known, monitored risk — Certain targeted therapies increase the likelihood of clots in the veins or, less commonly, the arteries.
- Two different types of clot — Vein clots (DVT, pulmonary embolism) and arterial events (stroke, heart attack) have different symptoms — both need urgent action.
- Stroke symptoms need 112 now — Sudden weakness, speech difficulty, or face drooping are emergencies. Do not wait to call your cancer team.
- A swollen leg needs a same-day call — New or one-sided leg swelling means contacting your oncology team today, not at your next scheduled visit.
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Several targeted therapies — particularly those affecting blood vessel growth signals — increase the risk of clots in the veins or arteries. NCCN and ASCO both list thromboembolic events as a recognised risk requiring active monitoring. A new swollen leg, sudden shortness of breath, or any stroke symptom means contacting your team or emergency services today.
If a symptom below applies to you, do not wait for a callback. Call 1800-202-8726 or go to your nearest emergency department.
What can you do at home every day while on targeted therapy?
- Check both legs each morning for new swelling, warmth, or redness — especially below the knee.
- Stay well hydrated. Dehydration makes blood thicker and raises the clot risk.
- Keep moving where your energy allows. Short walks help. Lying still for long periods does not.
- Tell your oncology team before any long journey by air or road so they can advise on precautions.
- Do not take aspirin, ibuprofen, or any blood-thinning supplement without asking your oncology team first.
- Tell your team about all herbal medicines or traditional remedies — some affect how blood clots.
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Trained at AIIMS, Tata Memorial, and leading international centres. Combined 150+ years of experience. Every complex case is reviewed by 3+ of them — together.
Medical Oncologist
Dr. C. Raghavendra Reddy
MBBS(Gold Medal), DNB(General Medicine), DM(Medical Oncology)(Gold Medal)
Medical Oncologist
Dr. Bharati Devi Gorantla
MBBS, MD(General Medicine), DM(Medical Oncology)(Adyar,Chennai), ECMO, MRCP SCE(UK)
Medical Oncologist
Dr. Owais Mohammed
MBBS, MD (General Medicine), DrNB (Medical Oncology), ECMO, MRCP SCE (Medical Oncology) (UK)
Medical Oncologist
Medical Oncologist
Surgical Oncologist
Dr. Muralidhar Muddusetty
MBBS (AIIMS), MS (Surgery) (AIIMS), DNB (Surgical Oncology), MRCS (Edinburgh)
Surgical Oncologist
Surgical Oncologist
Surgical Oncologist
Dr. Vinay Mamidala
MBBS, MS(General Surgery), M.Ch(Surgical Oncology), FMAS, FARIS(Ongoing)
Surgical Oncologist
Radiation Oncologist
Radiation Oncologist
Radiation Oncologist
Hematologist
Interventional Radiologist
Dr. Mohammed Imran
Surgical Oncologist
Dr. Vajja Sandeep Kumar
MBBS, MS (General Surgery), DrNB (Surgical Oncology), FALS Oncology
Surgical Oncologist
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How do you tell a call-today symptom from a go-now emergency?
| Symptom or sign | Call your oncology team today | Go to emergency now — call 112 |
|---|---|---|
| Leg swelling | One leg more swollen than the other, mild, came on over a day or two | Rapid onset, severe pain, or skin that looks purple or mottled |
| Shortness of breath | Slightly more breathless than usual on exertion, no chest pain | Breathlessness at rest, or alongside chest pain or a racing heart |
| Chest discomfort | Vague heaviness, not changing with breathing | Sharp pain that worsens when breathing in, or accompanied by sweating |
| Headache | Persistent new headache, not explained by another cause | Sudden, severe — described as the worst headache of your life |
| Vision changes | Blurring that came on gradually, one or both eyes | Sudden loss of vision in one eye, or double vision with dizziness |
| Face or arm weakness | Does not apply — any new weakness is an emergency | Sudden drooping or weakness on one side: call 112 immediately |
| Typically starts | DVT symptoms usually build over hours to a day or two | Stroke and pulmonary embolism symptoms are typically sudden — seconds to minutes |
Why do some targeted therapies raise the risk of blood clots?
Cancer itself alters how blood clots — this is well established in NCCN and ESMO guidance and is sometimes called a hypercoagulable state. Some targeted therapies add a further layer of risk by affecting the signals that regulate blood vessel walls.
Drugs that target VEGF (vascular endothelial growth factor) pathways — used in kidney, bowel, liver and other cancers — can affect the lining of blood vessels in ways that raise the risk of clots in both veins and arteries.
Other targeted therapies, including some used in leukaemia and myeloma, raise the risk specifically in the veins. Your oncologist will have weighed this risk against the expected benefit before recommending your specific treatment.
Your individual risk is not the same as the average. It is higher if you have had a clot before, have limited mobility, or have other conditions that affect clotting — and your team will have asked about these at the start of treatment.
What will your team do if they suspect you have a clot?
A suspected vein clot is usually confirmed with an ultrasound of the leg or a CT scan of the chest. Blood tests alone cannot rule it out, so imaging is needed.
If a clot is confirmed, treatment is typically a blood-thinning medicine — either a low-molecular-weight heparin injection or a direct oral anticoagulant tablet. Your oncology team will choose based on your other medications and your cancer treatment.
A confirmed clot does not automatically mean your targeted therapy has to stop. Your oncologist will assess the severity, the type of clot, and how essential your current treatment is, and explain the options clearly.
Follow-up after a clot is usually close. If blood thinners are prescribed, your team will tell you what signs of bleeding to watch for — because that is the main risk of anticoagulant treatment itself.
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Common questions
Frequently asked questions
Is a swollen leg always a blood clot on targeted therapy?
Not always — swelling can also come from fluid retention, steroids, low protein levels, or lymph node involvement. But on targeted therapy, a new swollen leg — especially if it is only one leg and comes with warmth or redness — is treated as a DVT until your team rules it out. Do not wait to see if it settles. Call your oncology team the same day so they can arrange an ultrasound if needed.
Can I fly while I am on targeted therapy?
Long-haul flights raise the clot risk for anyone, and that baseline is higher on some targeted therapies. Tell your oncology team before booking any flight longer than a few hours. They may advise on compression stockings, regular movement during the flight, or whether the timing is appropriate given your treatment. This is not an automatic reason to cancel travel — it is a conversation to have before you book rather than the night before you board.
My doctor mentioned taking a blood thinner to prevent clots. Is that standard?
In some situations, blood-thinning medicines are given preventively to people on cancer treatment who are at higher risk of clots. ASCO has published guidance supporting prophylactic anticoagulation for certain high-risk patients on cancer treatment, but it is not recommended for everyone. Whether it is right for you depends on your specific therapy, your cancer, your mobility, and other factors your oncologist will weigh. If it has been raised, ask your team directly what the expected benefit is and what the bleeding risk would be for you.
I take my targeted therapy as a tablet at home. Does the clot risk still apply to me?
Yes. Many oral targeted therapies carry the same vascular risks as intravenous ones, and the risk continues for as long as you are taking the tablet. Being at home rather than in a day-care setting does not reduce that risk — and it means you need to be more alert to symptoms yourself, because no nurse is observing you between visits. The same red flags apply whether your treatment is given by injection or by mouth.
What is the difference between a DVT and a pulmonary embolism?
A DVT (deep vein thrombosis) is a clot in a deep vein, most commonly in the leg. A pulmonary embolism happens when part of that clot breaks off and travels to the lungs, blocking blood flow there. A DVT needs prompt treatment, but a pulmonary embolism is immediately life-threatening. This is why a swollen leg on targeted therapy is treated as urgent rather than watchful-waiting — the concern is not just the clot where it formed but where it can travel.