This calculator is for general information and education. It is not medical advice and does not replace the judgment of a doctor, nurse or pharmacist who knows the full clinical picture.
Cancer and blood clots
People with cancer are several times more likely than others to develop venous thromboembolism (VTE): a deep vein thrombosis, usually in a leg, or a pulmonary embolism, a clot that travels to the lungs. Chemotherapy raises the risk further. Blood thinners can prevent clots but also cause bleeding, so the challenge is to identify the patients who will benefit most. In 2008 Alok Khorana and colleagues published a simple score for outpatients about to start chemotherapy, based on data from more than 4,000 patients.
The five items
| Item | Points |
|---|---|
| Very high-risk cancer site: stomach, pancreas | 2 |
| High-risk site: lung, lymphoma, gynecologic, bladder, testicular | 1 |
| Platelets 350,000/µL or more before chemotherapy | 1 |
| Hemoglobin below 10 g/dL, or use of red cell growth factors | 1 |
| White blood cells above 11,000/µL before chemotherapy | 1 |
| Body mass index of 35 kg/m² or more | 1 |
The total ranges from 0 to 6.
Risk by score
| Score | Risk group | VTE over about 2.5 months (original study) |
|---|---|---|
| 0 | Low | 0.3 to 0.8% |
| 1 to 2 | Intermediate | 1.8 to 2% |
| 3 or more | High | 6.7 to 7.1% |
Worked example
A patient with lung cancer (1 point) has a platelet count of 410,000/µL before the first chemotherapy cycle (1 point). Hemoglobin, white cells and BMI are normal. The Khorana score is 2: intermediate risk in the original categories, but at the threshold where guidelines suggest discussing prevention.
What guidelines say
The American Society of Clinical Oncology (ASCO) suggests that outpatients with cancer and a Khorana score of 2 or more before starting chemotherapy may be offered thromboprophylaxis with apixaban, rivaroxaban or low-molecular-weight heparin, provided they have no significant risk of bleeding and no drug interactions. Two trials published in 2019, AVERT and CASSINI, showed that preventive apixaban or rivaroxaban lowered the rate of clots in such patients, at the price of some additional bleeding.
Limits
- The score performs less well in some cancers, such as lung cancer, and does not include cancers like brain tumors or myeloma, which carry their own high risk.
- It does not account for other risk factors: a previous clot, recent surgery, a central venous catheter or certain drugs.
- Newer scores add markers such as D-dimer, but they are less widely used.
Warning signs
Seek medical care for pain, swelling or warmth in one leg or arm, or urgently for sudden shortness of breath, chest pain or coughing up blood, which may signal a pulmonary embolism.