High Risk for VTE in Postsurgical Lung Cancer Patients

Roxanne Nelson, RN

April 29, 2015

A postoperative venothromboembolic (VTE) event is a serious and potentially life-threatening complication of pneumonectomy, and the incidence of this event is higher than has previously been reported, concludes a new study.

The study, presented at the 95th annual meeting of the American Association for Thoracic Surgery, in Seattle, is the first prospective cohort analysis to assess the real incidence of postoperative VTE events after major lung resection, the investigators point out.

"The incidence is higher than previously reported," said lead author Yaron Shargall, MD, head of the Division of Thoracic Surgery and holder of the Juravinski Professorship in Thoracic Surgery at McMaster University, Hamilton, Canada. "All events happened among inpatients undergoing anatomical resections, either lobectomy or segmetectomy."

The team was unable to identify any specific risk factors in the cohort. "Most patients might be asymptomatic, indicating the need for either screening, which is less efficient and likely not realistic, or an extended prophylaxis beyond hospital discharge, as is the recommended treatment in other surgical specialties," Dr Shargall told Medscape Medical News.

Among patients who were diagnosed with a VTE, only four (21.1%) were acutely symptomatic at the time of diagnosis. All of the events were diagnosed after hospital discharge, and only because the patients were being screened for VTEs as part of the study protocol.

High PE Rate

For their study, Dr Shargall and colleagues evaluated outcomes for 157 patients who underwent thoracic surgery for primary lung cancer (89.9%) or metastatic cancer (6.3%).

All patients received unfractionated heparin or low-molecular-weight heparin and mechanical VTE prophylaxis (graduated compression stockings) perioperatively and until hospital discharge. In addition, participants underwent chest CT scans with pulmonary embolus (PE) protocol, as well as a Doppler ultrasound of the lower extremities approximately 30 days after surgery.

Patient demographics, preoperative comorbidities, histology, staging, perioperative complications, and VTE-related outcomes were recorded up to 3 months postoperatively.

A repeat scan was conducted 30 days postoperatively if the first scan was negative. Patients with VTEs were monitored and received appropriate treatment.

Among patients considered to be at high risk for VTE, 19 VTE events were detected, which extrapolated to a 12.1% incidence rate. These included 14 PEs (8.9%), three deep vein thromboses (DVTs) (1.9%), and one case of combined PE/DVT.

The 30-day mortality rate was 0.64% for the entire cohort but 5.2% for those who had a VTE.

The authors also found that preoperative comorbidities, previous malignancy, neoadjuvant therapy, staging, extent and type (thoracoscopy vs open) of surgical procedure, site of surgery, and perioperative events were not found to be significantly different between the event and overall cohorts on both independent parametric and nonparametric analysis.

Dr Shargall pointed out that his group is the only one thus far to prospectively assess patients by doing both venous Doppler and CT PE protocols.

"Since a very large proportion of our patients had PE without DVT, it highlights the fact that venous Doppler of the legs only might not be the right way to find those VTE events," he said. "Thoracic surgery patients might be a unique population with predisposition to PE post-op, perhaps due to direct local effect, such as manipulation and division of the blood vessels leading to the lung during the lung resection, leading to a local injury that might promote subsequent creation of local blood clots."

 
We are clearly at the point where thoracic surgery needs to design a prospective, randomized study. Dr Yaron Shargall
 

"But we are clearly at the point where thoracic surgery needs to design a prospective, randomized study checking the effect of prolonged prophylaxis for patients undergoing lung resection for malignancies," Dr Shargall added.

Routine Screening Ups Detection

In a related study presented at the same meeting, researchers from the Cleveland Clinic, in Ohio, evaluated the effects of a postoperative screening protocol on rates of VTEs to determine whether this strategy increased detection.

Led by Siva Raja MD, PhD, from the Department of Thoracic and Cardiovascular Surgery, they found that the diagnosis of VTE after pneumonectomy was nearly three times higher in patients who were screened, compared with those who were only tested when they developed symptoms.

The cohort included 112 patients who had undergone a pneumonectomy between 2006 and 2012 and who were enrolled in a care pathway that included a routine postoperative lower extremity VTE screen just prior to expected discharge. Their data were compared with those of a control group of 336 patients who underwent pneumonectomy without routine VTE screening.

Within this group, 20 patients developed a VTE following their surgery. Ten (50%) of them were asymptomatic but were found to have a VTE when screened in the hospital prior to discharge.

The percentage of in-hospital VTEs in the screened group was almost three times higher than in the control group (8.9% vs 3.0%; P = .008) and more than twice as high during the 30-day postoperative period (13% vs 5.0%; P = .007). A total of 14 patients (70%) had a VTE that was diagnosed within 30 days.

In both groups, the authors noted that the risk for VTEs peaked about 6 days after pneumonectomy, which was approximately the day of discharge, and reached a plateau after 30 days. The presence of a VTE was associated with a worse long-term survival (hazard ratio, 2.1; P = .08).

Routine screening for VTE after pneumonectomy was implemented at the Cleveland Clinic in 2006. "It is possible that the prevalence of VTE may be even higher should a comprehensive serial screening program be initiated," Dr Raja commented in a statement.

Caprini RAM Effective in Thoracic Surgery

A third study presented at the meeting addressed the question of how to identify postsurgical lung cancer patients who are at the greatest risk of developing a VTE. Virginia R. Litle, MD, associate professor of surgery, Boston University School of Medicine, in Massachusetts, and colleagues found that the Caprini Risk Assessment Model (RAM) can be used to stratify postsurgical lung cancer patients according to VTE risk.

The Caprini RAM is used to assess VTE risk in other surgical specialties, including general, vascular, and plastic surgery, as well as gynecologic oncology, but not in thoracic surgery. It comprises 42 variables, including age, body mass index, prior VTE history, and a history of chemotherapy, laparoscopic surgery, and open surgery.

"This is the first report of examining the Caprini RAM specifically in lung cancer resection patients," Dr Litle told Medscape Medical News. "This risk assessment scoring system can be used to determine which lung resection patients may potentially benefit from preventive blood thinner therapy after discharge."

The authors conducted a retrospective chart review of 232 patients who underwent lung resection from 2005 to 2013. All patients were categorized into one of five risk groups on the basis of a modified Caprini scoring system: lowest risk (score 0), low risk (1-2), moderate risk (3-4), high risk (5-8), or highest risk (>9).

The overall 60-day postoperative VTE incidence was 5.17% (12/232), with 50% (6/12) having a PE.

The mean Caprini score was significantly higher among patients who developed VTEs compared with those who did not (11.83 ± 3.74 vs 8.07 ± 2.84; P < .001). In the low- to moderate-risk group, the incidence of VTEs was 0%, compared with 1.67% in the high Caprini score group and 10.42% for those with the highest Caprini scores.

One death was recorded, from a patient with PE whose score of 16 fell within the highest-risk Caprini group. When 9 was used as the cutoff for highest risk, the RAM had an 80% sensitivity, a 60.9% specificity, and a 61.2% accuracy.

This risk assessment scoring system can be used to determine which patients may potentially benefit from prophylactic anticoagulant therapy after discharge, explained Dr Litle.

"I do consider it beneficial to apply the tool; however, we do not yet have the prospective, randomized trial," she said. "We are looking at our patients prospectively now and are planning on a larger, multicenter trial in which we can randomize."

Dr Shargall's study was funded by the Heart and Stroke Foundation of Canada.

95th Annual Neeting of the American Association for Thoracic Surgery. Presented April 27 and 28, 2015.

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