Late venous thromboembolism in survivors of adolescent and young adult cancer: A population-based study in California.

[INTRODUCTION] Venous thromboembolism (VTE), a common complication in cancer patients, occurs more often during the initial phase of treatment. However, information on VTE beyond the first two years after diagnosis ('late VTE') is scarce, particularly in young survivors.

[METHODS] We examined the risk of, and factors associated with, late VTE among adolescents and young adults (AYA, 15-39 years) diagnosed with cancer (2006-2018) who survived ≥2 years. Data were obtained from the California Cancer Registry linked to hospitalization, emergency department and ambulatory surgery data. We used non-parametric models and Cox proportional hazard regression for analyses.

[RESULTS] Among 59,343 survivors, the 10-year cumulative incidence of VTE was 1.93 % (CI 1.80-2.07). The hazard of VTE was higher among those who had active cancer, including progression from lower stages to metastatic disease (Hazard Ratio (HR) = 10.41, 95 % confidence interval (CI): 8.86-12.22), second primary cancer (HR = 2.58, CI:2.01-3.31), or metastatic disease at diagnosis (HR = 2.38, CI:1.84-3.09). The hazard of late VTE was increased among survivors who underwent hematopoietic cell transplantation, those who received radiotherapy, had a VTE history, public insurance (vs private) or non-Hispanic Black/African American race/ethnicity (vs non-Hispanic White). Patients with leukemias, lymphomas, sarcoma, melanoma, colorectal, breast, and cervical cancers had a higher VTE risk than those with thyroid cancer.

[CONCLUSIONS] VTE risk remained elevated ≥2 years following cancer diagnosis in AYA survivors. Active cancer is a significant risk factor for VTE. Future studies might determine if late VTE should prompt evaluation for recurrence or second malignancy, if not already known.