What Is Pulmonary Embolism, and Why Is It Increasing in Patients With Cancer?

What Is Pulmonary Embolism?

Pulmonary embolism (PE) occurs when a blood clot, usually formed in the deep veins of the legs (deep vein thrombosis), breaks away, travels to the lungs, and blocks the pulmonary arteries. This blockage of blood vessels in the lungs obstructs blood flow and can be life-threatening.

Embolism Risk in Patients With Cancer

PE can cause sudden breathlessness, chest pain, and even sudden death. It has long been recognized as an important risk in patients with cancer because of increased clotting tendency. However, new research indicates a growing threat by showing that PE-related deaths among patients with cancer have increased substantially in recent years . Despite progress in cancer treatment, rising PE incidence reveals a hidden risk facing these patients.

Striking Findings From the Study

A large study published in JAMA Network Open found that PE-related deaths among US patients with cancer increased by 44.3% between 2011 and 2020 . This represents an increase of nearly half over almost a decade. On average, there was an approximately 2.9% annual increase in PE-related deaths . In other words, nearly 3% more patients with cancer died from a pulmonary clot each year than in the previous year. The trend was highly statistically significant (p < 0.001), indicating a rise too marked to be readily explained by chance.

The researchers particularly noted that the age-adjusted mortality rate , which accounts for changes in population age distribution, increased by 2.5% annually. Thus, the rise cannot be attributed solely to population aging; other factors also contribute. 

Which Patient Groups Face Greater Risk?

The analysis examined trends across age groups, sexes, and ethnic backgrounds. Among younger patients with cancer aged 15-64, PE-related mortality increased by an average of 3.2% annually, whereas among patients aged 65 and older  the corresponding annual increase was 2.7%. The increase was therefore slightly greater in younger patients. This is noteworthy because older patients are generally thought to face greater risk, but these data show that younger patients also face serious risk.

By sex, women and men with cancer experienced similar upward trends. PE-related deaths increased by an average of 2.7% annually in women and 2.3% in men. Both increases were statistically significant, meaning that mortality from pulmonary embolism increased compared with earlier years in both sexes.

Ethnic and racial groups also showed marked increases. White patients with cancer had an approximately 2.7% annual increase in PE-related mortality. Hispanic patients showed a similar increase of approximately 2.6% annually. Black (African American) patients had an annual increase of 2.2%. Asian or Pacific Islander patients showed an annual increase of approximately 2.0%, but it was not statistically significant. This suggests that the smaller observed increase might reflect chance or that population size limited clear conclusions. Nevertheless, the overall pattern indicates that PE-related mortality risk rose in almost all subgroups, regardless of ethnic background .

Why Is Pulmonary Embolism Increasing?

What might explain such a substantial rise in pulmonary embolism-related deaths among patients with cancer? The researchers emphasize that it may not have a single cause, but instead reflect several factors acting together .

The first possibility is better recognition and more frequent diagnosis of PE today . Clinicians have become more aware of clotting problems in patients with cancer. Guidelines on cancer-associated thrombosis and increased awareness allow more accurate detection of cases previously missed. Death certificates, for example, may now record pulmonary embolism as a cause more carefully. More cases entering the statistics may therefore contribute to the apparent increase. Patients may have had PE in earlier years too, but some cases went unrecognized; detection has now improved.

The Effects of Obesity, Diabetes, and Chronic Disease

Another important factor is the growing prevalence of lifestyle and health conditions that increase clotting risk. Obesity and diabetes , for example, are recognized risk factors for increased clotting tendency. Obesity rates have risen globally over the past decade. Patients with cancer share these additional risks with the general population. Combined with cancer, they substantially increase clot formation risk. Thus, a larger number of patients having these risk factors may have contributed to more PE cases being observed.

The Role of Cancer Treatments in Thrombosis

Another consideration is the effect of cancer treatments themselves on clotting. Modern treatments, including some targeted medicines, hormonal therapies, and immunotherapies, prolong life but may increase clotting risk as a side effect. Medicines for certain cancers particularly predispose to intravascular clots. As their use expands, patients who survive or live longer may become more likely to develop PE over time.

Changes in Cancer Cases and Survival

An interesting finding was that, over the same period (2011-2020), age-adjusted incidence of newly diagnosed cancer in the US , accounting for population size and age structure, declined. New cancer incidence fell from 470.9 per 100,000 people in 2011 to 403.3 in 2020, equivalent to an average annual reduction of 1%. Proportionately, cancer risk therefore appears to be declining slightly. The decrease was statistically significant (p = 0.01) and may reflect screening, prevention, and lifestyle changes.

Absolute numbers, however, show a different picture: New cancer cases rose from 1,613,893 in 2011 to 1,818,739 in 2019; the 2020 data may be less reliable because of the pandemic. Total new cases therefore increased. How can rates fall while counts rise? Population growth and aging explain the apparent contradiction. As the population grows and more people reach older ages, total cases increase even if the rate of developing cancer declines slightly. In other words, fewer people per 100,000 may develop cancer, but a larger total population produces more diagnoses in absolute terms.

The Consequences of Living Longer With Cancer

A similar pattern occurred in cancer-related mortality rates over this period. Age-adjusted cancer mortality fell from 168.8 per 100,000 in 2011 to 143.8 in 2020, an average annual decrease of 1.8%. This is encouraging: treatment progress is improving survival, and proportionately fewer people die of cancer. Yet population effects also apply here. The total number of cancer deaths rose from 576,685 in 2011 to 602,347 in 2020. Absolute deaths therefore increased slightly because the population, and consequently the number of patients with cancer, is larger.

What does this apparent paradox have to do with PE? As patients generally live longer after diagnosis, even those with advanced or high-risk cancers now survive longer than in earlier years. Unfortunately, this also gives them more time to develop additional risks such as PE. Previously, a very aggressive cancer might have caused death within a few years. New treatments now allow longer survival and a more chronic experience of illness. Other problems may accumulate during that time: prolonged treatment side effects, cardiovascular strain, infections, periods of inactivity, or additional diseases such as hypertension or heart disease. Together, these factors increase the risk of a thromboembolic event at some point during the prolonged illness. Ironically, better cancer control therefore brings into focus the risk of death from a clot in these patients.

The researchers highlight precisely this point: longer survival resulting from progress in cancer care means that doctors and patients must also prepare for other risks . Healthcare systems need a proactive approach to prevent complications from overshadowing longer life.

Clinical Implications

The findings carry important messages for clinicians and patients. Pulmonary embolism can be a preventable cause of death : appropriate measures can prevent many cases or allow early detection and treatment. PE risk therefore deserves greater attention than ever during cancer follow-up.

Identifying high-risk patients is crucial. Clinical tools such as the Khorana score help assess clotting risk. The study emphasizes the importance of risk assessment and thromboprophylaxis, meaning clot-preventing treatment. Doctors may more frequently reassess whether preventive anticoagulation is needed, particularly in advanced cancer or prolonged treatment. This decision must of course balance factors such as bleeding risk while taking the increased PE threat into account.

It is also vital to educate patients about PE symptoms . They should seek immediate medical attention for breathlessness, sudden chest pain, unexplained rapid fatigue, or leg swelling and pain, because an early-diagnosed pulmonary embolism may not be fatal if treated promptly. Recognizing these symptoms can be lifesaving for both patients and healthcare workers in a setting of increasing risk.

Finally, the findings also matter for health policy and guidelines . Screening for thromboembolism and establishing preventive treatment protocols may be considered. The researchers note that the new data may support updates to thrombosis-prevention guidelines to protect this vulnerable population . Strategies such as routine low-dose heparin for hospitalized patients with cancer or risk-based prophylaxis during chemotherapy therefore become more important.

Conclusion

Although progress against cancer is encouraging, pulmonary embolism risk emerging as an unexpected consequence of that success requires attention. The substantial rise in PE-related deaths over the past decade reminds us of the importance of holistic care. Treatment must address general health, additional risks, and side effects as well as the tumor.

The study shows that a multidisciplinary approach is essential in caring for patients receiving cancer treatment . Oncologists, cardiologists, hematologists, and other specialists should work together both to treat cancer and protect against complications.

Remember that every statistic represents a human life. Recognizing that patients may die not only of cancer but also of other cancer-associated causes calls for greater attention to these areas. Reducing deaths from preventable causes such as PE should be integral to cancer care. As life expectancy improves, quality of life and safety can improve alongside it.