Risk of Venous Thromboembolism Increases After Cancer Surgery, Study Finds

Patients who underwent major surgery for 8 cancer types experienced an increased rate of venous thromboembolism associated with cancer surgery, according to one study.

These findings highlight the need for venous thromboembolism risk evaluation and prophylaxis regimens for patients undergoing surgery for different cancers.

Blood sample test with positive diagnosis of thrombosis risk in a coagulation test | angellodeco - stock.adobe.com

“Venous thromboembolism is a rare unintended outcome after surgery that is particularly suitable for research using clinical data,” wrote the researchers of the study. “We were able to use the Swedish health care and population registers, which are known for their high coverage, completeness, and accuracy, to assemble a large cohort of patients who underwent cancer surgery and estimate risks in comparison with a matched population with high statistical precision.”

This large, nationwide cohort study is published in JAMA Network Open.

Because the risks and benefits of thromboprophylaxis therapy after cancer surgery are debated, this study aimed to evaluate the 1-year risk of venous thromboembolic events after major cancer surgery and how these events vary over time.

The researchers utilized data on the full population of Sweden between 1998 and 2016, and included all patients who underwent major surgery for bladder, breast, colon or rectum, gynecologic organ, kidney and upper urothelial tract, lung, prostate, or gastroesophageal tract cancer. These patients were matched 1:10 with cancer-free individuals of the general population of the same year of birth, sex, and country of residence.

The main outcome was the incidence of venous thromboembolic events within 1 year after surgery. Additionally, the researchers evaluated the crude absolute risks and risk differences of events within 1 year and adjusted time-dependent cause-specific hazard ratios (HRs) of post discharge events. The statistical analysis was conducted from February 13, 2023, to December 5, 2023.

A total of 432,218 patients with cancer and 4,009,343 cancer-free individuals were included in the study. Breast (37.7%) and colorectal (26.3%) cancer were the largest tumor groups within the cancer surgery cohort, respectively. Additionally, the median (IQR) length of hospitalization varied between the different cancer types from 2 (1-4) days for breast cancer to 17 (13-17) days for bladder cancer.

Moreover, the crude 1-year cumulative risk of pulmonary embolism was highest among the cancer surgery population, with the following absolute risk differences:

• Bladder cancer, 2.69% (95% CI, 2.33-3.05)
• Breast cancer, 0.59% (95% CI, 0.55-0.63)
• Colorectal cancer, 1.57% (95% CI, 1.50-1.65)
• Gynecologic organ cancer, 1.32% (95% CI, 1.22-1.41)
• Kidney and upper urinary tract cancer, 1.38% (95% CI, 1.21-1.55)
• Lung cancer, 2.61% (95% CI, 2.34-2.89)
• Gastroesophageal cancer, 2.13% (95% CI, 1.89-2.38)
• Prostate cancer, 0.57% (95% CI, 0.49-0.66)

Additionally, the cause-specific HR of pulmonary embolism peaked shortly after discharge and generally plateaued 60 to 90 days later. Thirty days after surgery, the HR was 10 to 30 times higher than in the comparison cohort for all cancer except breast cancer:

• Colorectal cancer (HR, 9.18; 95% CI, 8.03-10.50)
• Lung cancer (HR, 25.66; 95% CI, 17.41-37.84)
• Breast cancer (HR, 5l.18; 95% CI, 4.45-6.05)

While these HRs subsided, they never reached the level of the comparison cohort except for prostate cancer, and similar results were seen for deep vein thrombosis.

The researchers acknowledged some limitations to the study. First, the study lacked information pertaining to treatments besides surgery that may be associated with increased risk of venous thromboembolism. Additionally, the researchers noted how changes in clinical practices and diagnostics over time could affect both the occurrence and detection of outcomes.

Despite these limitations, the researchers believe the study suggests an elevated risk of postoperative venous thromboembolic events among patients who underwent cancer surgery.

“The 1-year postoperative risks of pulmonary embolism or deep vein thrombosis were different for different cancers, ranging from 0.57% to 4.67%, which should be considered in future prophylactic regimens,” wrote the researchers. “The results highlight the need for individualized venous thromboembolism risk evaluation and prophylaxis regimens for patients undergoing surgery for different cancers.”

Reference

Björklund J, Rautiola J, Zelic R, et al. Risk of venous thromboembolic events after surgery for cancer. JAMA Network Open. Published online: February 2, 2024. doi:10.1001/jamanetworkopen.2023.54352