Critical link between pulmonary embolism and cancer: know the causes and analyze the symptoms

Pulmonary embolism is a serious condition characterized by the partial or total obstruction of a pulmonary artery, or one of its branches, by a blood clot. It occurs, in most cases, when blood clots formed in the deep veins of the legs (deep vein thrombosis) detach and travel to the lungs. They block blood flow, and therefore the oxygen supply to the part of the lungs that is no longer supplied. This can lead to tissue necrosis – this is known as pulmonary infarction – and leads to reduced oxygenation of the rest of the body. 

In cancer patients, the risk of pulmonary embolism is increased fourfold. Prolonged immobilization and bed rest that may occur during hospitalization lead to a slowing of the blood circulation, making the formation of a thrombosis more likely. But cancer itself and its treatments are important additional factors.

Chemotherapy and risks of thrombosis

Indeed, some tumor cells produce an enzyme (cysteine protease) that activates the coagulation cascade. In some cases, tumor cells can penetrate the vascular network themselves and obstruct blood flow. Surgical procedures or the insertion of a venous catheter damages the vessels and reduces vascular tone. Finally, chemotherapies have multiple consequences.

Although they do not all increase the risk of thrombosis to the same extent, some may damage the walls of blood vessels, cause an imbalance in blood clotting by decreasing the number of platelets or cause systemic inflammation, accelerating the formation of blood clots. 

In addition, many cancer patients are elderly and have comorbidities that promote pulmonary embolism, such as hypertension, diabetes or coronary heart disease. This is why pulmonary embolism is the second leading cause of death in these patients. 

Patients sometimes tend to downplay their symptoms

Unbeknown to them, patients can confuse their symptoms with the side effects of the treatment, and ignore them. This is why it is important that medical staff maintain regular dialog with them and know how to recognize the associated signs. 

Pain in the leg, most often in the calf, associated or not with a swollen, hard, sometimes red leg, is an indication of venous thrombosis (also called phlebitis), which causes the embolism. Other symptoms may vary depending on the size of the blood clot and the area of the lungs affected. The most common symptom is breathlessness, which gets worse with exertion. Sudden and intense chest pain, made even more painful by deep breathing, should signal the alert. A sudden and persistent cough may appear, with or without blood in sputum. Heart rate can sometimes increase significantly (tachycardia). Excessive sweating, cold sweats and dizziness are other signs to look out for.

The diagnosis is made difficult by the fact that these signs are not always present and vary in intensity from one person to another. Possible screening tests are chest x-ray, electrocardiogram, blood gases, and D-dimers. They must be confirmed by computed tomography or pulmonary scintigraphy.

¹ https://francais.medscape.com/voirarticle/3604222
² https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4348145/