Prophylactic Approach to Cancer-Related Thrombosis May Be Optimal

Patients with cancer are at a significant risk of developing a thrombotic event for multiple reasons, with the occurrence of these events directly associated with a significant increase in mortality, explained Victoria Nachar, PharmD, BCOP, clinical pharmacist specialist-ambulatory hematology oncology at the University of Michigan Rogel Cancer Center, during a session at the Hematology/Oncology Pharmacy Association 2021 Virtual Annual Conference.

Even while therapeutically anticoagulated, patients with cancer have risk factors for both recurring venous thromboembolism (VTE) and bleeding, which makes clinicians’ assessments of the treatment prospects in relation to cancer-related VTE quite complex, especially for patients with a fluctuating clinical status. Additionally, the molecular mechanisms that cause this predisposition remain poorly understood, which makes treatment difficult.

Nachar explained that the oldest and most dominant theory regarding the potential predisposition for VTE in patients with malignancy is that there are 3 components for clinicians to assess: the blood, the blood vessel wall, and the blood flow.

“We often see that our patients have multiple abnormalities in each of these 3 components, and so likely, the mechanisms behind cancer-related VTE are multiple and they are probably synergistic,” Nachar said during the session.

In this way, all cancers may not lead to a predisposition for VTE at the same rate, explained co-speaker Allison Schepers, PharmD, BCOP, clinical pharmacist specialist in Inpatient Medical Oncology at the University of Michigan Medicine, during the session. Although almost all cancer subtypes do present with a markedly increased risk of VTE in comparison to non-cancer control, patients with the highest risk of VTE are specifically those with pancreatic or thoracic malignancies.

However, the site of malignancy is not the only factor that puts patients with cancer at an increased risk.

“In addition to the site of malignancy, there are a variety of patient malignancy and treatment-related factors that also increase risk,” Schepers said during the session. “We know that comorbidities such as obesity, renal dysfunction, and infection can increase a person’s risk, as well as disease characteristics, such as metastatic disease or being in the first few months since the cancer diagnosis.”

Schepers noted that for pharmacists, of utmost concern are the treatment modalities available in light of these risk factors, and which cancer treatments may contribute to them. Common cancer treatments such as cisplatin, vascular endothelial growth factor (VEGF) inhibitors, immunomodulators, and hormonal therapies are some of the greatest culprits of the increased risk for the development of VTE in patients with cancer, according to Schepers.

Additionally, Schepers explained that since cancer-related VTE has such a high morbidity and mortality rate, the identification of those patients at the highest risk can allow for a prophylactic approach, which is optimal because it allows for the avoidance of such complications before they occur.

“Luckily, we do have a validated scoring tool, the Khorana Score, that takes a variety of factors into account and assigns a score, with a higher Khorana Score being associated with a higher risk of developing a VTE,” Schepers said during the session.

However, although cancer-related VTE is a relatively common complication for patients, the treatment for VTE continues to be anything but simple, Schepers explained. Patients with cancer are at a 6 times increased risk of recurrent VTE than non-cancer patients, but they are also at higher risk for other adverse effects as well, such as bleeding.

Additionally, these patients often need anticoagulation treatment in the longer-term, which has a significant effect on quality of life for this population, as well as bringing forth concerns regarding adherence due to the extended duration of treatment and issues that may arise as a result.

“All of these factors really come together to form a very complex picture of how best to treat cancer-related VTE,” Schepers said during the session.

REFERENCE

Nachar V, Schepers A. Cancer-Related Thrombosis: The Great Debate on the Best Way to Anticoagulate. Presented at: Hematology/Oncology Pharmacy Association 2021 Virtual Annual Conference; April 13, 2021; virtual. Accessed April 14, 2021.