Two Studies Examine the Significant Postoperative Risk of Life-Threatening Blood Clots in Patients With Lung Cancer
New evidence suggests that patients with lung cancer who undergo surgery are at higher risk of developing venous thromboembolism, including deep-vein thrombosis and pulmonary embolism, than previously thought, with elevated risks of complications or death. When thromboemboli occur, they may be asymptomatic or attributed to postsurgical pain or complications and may reflect both the lung cancer itself as well as compromised lung function after surgery. These incidents may also be ascribed to an inconsistent approach to prevention that currently exists among thoracic surgeons and hematologists who care for these patients. Two presentations at the 95th Annual Meeting of the American Association for Thoracic Surgery explored the problem of venous thromboembolism after surgery for lung cancer.
Incidence of Venous Thromboembolism After Lung Cancer Resection
In the first report, Yaron Shargall, MD, Head of the Division of Thoracic Surgery and Juravinski Professor of Thoracic Surgery at McMaster University, and colleagues presented the results of the first prospective analysis of the incidence of venous thromboembolism following oncologic lung resection. This study looked at outcomes for 157 patients who underwent thoracic surgery for primary lung cancer (89.9%) or metastatic cancer (6.3%). All patients received blood thinners (unfractionated heparin or low-molecular-weight heparin) and mechanical venous thromboembolism preventive treatment (graduated compression stockings) from the time of surgery until leaving the hospital.
Two weeks later, these patients were evaluated for the presence of venous thromboembolism signs and symptoms. Clinical outcomes were evaluated at 30 ± 5 days postoperatively using computed tomography (CT), pulmonary angiography, and bilateral Doppler venous ultrasonography. Patients who had developed symptoms suggestive of venous thromboembolism within the 30 days after surgery underwent urgent CT-pulmonary embolism examination and a repeat scan 30 days postoperatively if the first scan was negative. Patients with venous thromboembolism were monitored and treated.
Increased Mortality Among Those With Venous Thromboembolism
In this group of patients considered to be at high risk of venous thromboembolism because of their lung cancer, investigators found 19 venous thromboembolism events, a 12.1% incidence rate. They included 14 pulmonary embolisms (8.9%), three deep-vein thromboses (1.9%), and one combined pulmonary embolism/deep-vein thrombosis. One patient developed a massive left atrial thrombus originating from a surgical stump and died. For all 157 patients, the 30-day mortality rate was 0.64% but 5.2% for those who had venous thromboembolism. “This demonstrates the clinical importance and relative fatality of venous thromboembolism following lung cancer surgery,” explained Dr. Shargall.
All those diagnosed with venous thromboembolism had undergone anatomic resection (lobectomy or segmentectomy), and most had primary lung cancer. The clots tended to form on the same side as the lung surgery. The majority developed lung clots without forming deep-vein thromboses beforehand. The investigators examined factors that might distinguish those who developed clots from those who did not and could not find differences in age, lung function, length of hospital stay, comorbidities, lung cancer stage, smoking status, or Caprini Score.
Among patients diagnosed with venous thromboembolism, only four (21.1%) showed symptoms. All the events were diagnosed after the patient left the hospital and only because the patients were screened for venous thromboembolism as part of the study. “This study shows that a significant proportion of lung cancer surgery patients are at risk of venous thromboembolism and indicates a need for future research into minimizing the occurrence of deep-vein thrombosis and pulmonary embolism. It is possible that extended use of blood thinners beyond hospital discharge may reduce the number of patients who experience these life-threatening events and may help to reduce the rates of death after lung surgery,” stated Dr. Shargall.
Effect of Postoperative Screening
In a second study, researchers from the Cleveland Clinic assessed the effects of postoperative screening on rates of venous thromboembolism. Siva Raja, MD, PhD, of the Heart and Vascular Institute, Department of Thoracic and Cardiovascular Surgery, reported on the incidence of venous thromboembolism in 112 patients who underwent a pneumonectomy for benign and malignant indications. The patients were screened for these complications and compared with rates of a previously published group of 336 similar patients who did not undergo venous thromboembolism screening.
The researchers found that the percentage of in-hospital venous thromboembolism in the screened group was almost three times higher than those not screened (8.9% vs 3.0%) and more than twice as high during the 30-day postoperative period (13% vs 5.0%). In the screened group, 10 of 112 patients had venous thromboembolism detected by screening just before discharge, and four additional patients developed symptomatic venous thromboembolism within 30 days despite a negative predischarge screen. The risk of venous thromboembolism peaks 6 days after surgery.
At the Cleveland Clinic, routine screening for venous thromboembolism after pneumonectomy prior to discharge was adopted in 2006. “We find that a large proportion (50%) of venous thromboembolisms occurred prior to the time of discharge, and the risk of developing symptomatic venous thromboembolism remained elevated for 30 days. It is possible that the prevalence of venous thromboembolism may be even higher, should a comprehensive serial screening program be initiated,” noted Dr. Raja.
Venous thromboembolism is a particular problem after pneumonectomy, since these patients often have low pulmonary reserve to withstand the impact of pulmonary embolism, commented Dr. Raja. Indeed, this study also showed that post-pneumonectomy patients who developed venous thromboembolism faced a higher risk of death than those who did not. For this reason, Dr. Raja suggests that these patients be given blood thinner medications for a longer duration as well as undergo a repeat screening test for venous thromboembolism, even after discharge.
The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.
