Extended Pharmacologic Prophylaxis for Venous Thromboembolism After Colon Cancer Surgery Is Associated With Improved Long-term Survival: A Natural Experiment in the Chemotherapeutic Benefit of Heparin Derivatives.

Objective: This large database study assessed whether extended pharmacologic prophylaxis for venous thromboembolism after colon cancer resection was associated with improved oncologic survival.

Background: Heparin derivatives may confer an antineoplastic effect via a variety of mechanisms (eg, inhibiting angiogenesis in the tumor microenvironment). Studies evaluating the oncologic benefit of heparin and its derivatives have been limited in postsurgical patients. Multiple society guidelines recommend consideration of 30-day treatment with low molecular weight heparin to reduce venous thromboembolism risk after abdominopelvic cancer surgery. However, utilization of extended prophylaxis remains low.

Methods: Surveillance, Epidemiology, and End Results-Medicare data were used to identify patients (age 65+) undergoing resection for nonmetastatic colon cancer from 2016 to 2017. The primary outcomes were overall and cancer-specific survival. Log-rank testing and multivariable Cox regression compared survival in patients who received extended prophylaxis versus those who did not in an inverse propensity treatment weighted cohort.

Results: A total of 20,102 patients were included in propensity-weighting and analyzed. Eight hundred (3.98%) received extended pharmacologic prophylaxis. Overall survival and cancer-specific survival were significantly higher in patients receiving prophylaxis on log-rank tests ( P =0.0017 overall, P =0.0200 cancer-specific). Multivariable Cox regression showed improved overall survival [adjusted hazard ratio 0.66 (0.56-0.78)] and cancer-specific survival [adjusted hazard ratio 0.56 (0.39-0.81)] with prophylaxis after controlling for patient, treatment, and hospital factors.

Conclusions: Extended pharmacologic prophylaxis after colon cancer resection was independently associated with improved overall and cancer-specific survival. These results suggest a potential antineoplastic effect from heparin derivatives when used in the context of preventing postsurgical venous thromboembolism.