High total bilirubin level is a significant risk factor for severe neutropenia in patients receiving irinotecan-based chemotherapy.

Irinotecan is effective for the treatment of metastatic colorectal cancer (mCRC) and advanced pancreatic cancer (aPC). However, these treatments are often limited due to the incidence of severe neutropenia. We identified risk factors for severe neutropenia in patients with mCRC or aPC, receiving irinotecan-based chemotherapy regimens. The study selected 104 patients (mCRC: 53 and aPC: 51) who received irinotecan-based chemotherapy between January 2014 and May 2018 and who were included in the present study. The initial dose of irinotecan was 150 mg/m2 in all patients, and patients with a lower initial dose of irinotecan were excluded. Severe neutropenia (grade ≥ 3) occurred in 56 patients (53.8%). Multivariable Cox proportional hazards analysis indicated that modified FOLFIRINOX (mFOLFIRINOX) and serum total bilirubin (T-Bil) were significant risk factors for severe neutropenia. Moreover, with receiver-operating characteristic (ROC) curve analysis, the cutoff for T-Bil was found to be 0.7 mg/dL. Among patients treated with mFOLFIRINOX therapy, the incidence of severe neutropenia was significantly higher in patients with high level of T-Bil (> 0.7 mg/dL) than in those without it (93.8% vs 55.0%, P = 0.006). A chemotherapy regimen (modified FOLFIRINOX therapy) and T-Bil > 0.7 mg/dL were significant risk factors for severe neutropenia in patients receiving 150 mg/m2 irinotecan.