Relationship between severity and duration of chemotherapy-induced neutropenia and risk of infection among patients with nonmyeloid malignancies.

PURPOSE: Chemotherapy-induced neutropenia (CIN) may increase infection risk for cancer patients; however, there is limited understanding on the quantitative relationships between severity and duration of CIN and infection risk. METHODS: This study combined individual data from adult cancer patients receiving no granulocyte colony-stimulating factor during the first chemotherapy cycle in six trials. We used area over the curve (AOC) of absolute neutrophil count (ANC) time-response curve (below different thresholds) to measure the combined effect of severity and duration of CIN. Time-dependent Cox proportional hazards models quantified the hazard of first infection associated with duration of grade 4 or grade 3/4 CIN and the hazard associated with AOC. RESULTS: We analyzed data from 271 patients who had small cell lung cancer, non-Hodgkin's lymphoma, head and neck cancer, or breast cancer; 63.8 % of the patients had advanced cancer, and 77.5 % received chemotherapy regimens with high risk of febrile neutropenia. In the first cycle, 18.8 % of the patients had infection-related hospitalizations. Each additional day patients had grade 3/4 or grade 4 CIN was associated with 28 % (95 % CI 7, 51 %) and 30 % (95 % CI 10, 54 %) increased risk of infection-related hospitalization, respectively. Each unit increase in AOC (day × 10(9)/L ANC), with threshold of ANC < 0.5 × 10(9)/L, was associated with a significantly increased risk of infection-related hospitalization (hazard ratio 1.98; 95 % CI 1.35, 2.90). CONCLUSIONS: Infection risk increases dramatically with each additional day of grade 3 or 4 CIN. Interventions limiting CIN severity and duration are of critical importance to reduce infection risk in cancer patients receiving chemotherapy.