Risk factors for venous thromboembolism induced by prolonged bed rest during interstitial brachytherapy for gynecological cancer: a retrospective study

BACKGROUND: Screening and management of venous thromboembolism (VTE) after surgery is important in preventing sublethal VTE. However, the risk factors for VTE during interstitial brachytherapy (ISBT) remain unknown, and appropriate screening and management strategies are yet to be established. Therefore, this study aimed to evaluate the risk factors for VTE resulting from requisite bed rest during ISBT for gynecologic cancers. METHODS: We retrospectively analyzed 47 patients. For patients without definitive preceding radiotherapy, whole pelvic irradiation (30–50 Gy) followed by ISBT of 12–30 Gy/2–5 fx/1–3 days was administered to CTV D90. For patients with preceding radiotherapy, 36–42 Gy/6–7 fx/3–4 days was delivered by ISBT alone. The supine position was required during ISBT. D-dimer (DD) was measured at initial presentation, 1 week before ISBT, pre-ISBT, on the day of, and the day following needle removal. Patients were divided into three groups according to the risk of VTE and were managed accordingly; Group 1: DD was not detected (negative) before ISBT, Group 2: VTE was not detected on venous ultrasound imaging, although DD was positive before ISBT, and Group 3: VTE was detected (positive) before ISBT. An intermittent pneumatic compression device was used during ISBT; for the patients without VTE before ISBT. Heparin or oral anticoagulants were administered to patients with VTE before ISBT. RESULTS: Overall, the median values of DD pre-ISBT, on the day of, and on the day following needle removal were 1.0 (0.4–5.8), 1.1 (0.5–88.9), and 1.5 (0.7–40.6) μg/mL, respectively. After ISBT, no patients had deep vein thrombosis (DVT) in groups 1 and 2. In group 3, 7 of 14 patients experienced worsening of VTE but remained asymptomatic. In univariate analysis, DVT diagnosed before ISBT, Caprini score ≥ 7, and difference in DD values between pre-ISBT and the day of or the day following needle removal ≥ 1 were associated with the incidence or worsening of VTE. CONCLUSION: DD should be measured before and after ISBT to detect the incidence or worsening of VTE in patients with DVT. The Caprini score may help in the prediction of VTE during or after ISBT.