Early lymphopenia as a risk factor for chemotherapy-induced febrile neutropenia

Febrile neutropenia (FN) is a frequent complication of cancer chemotherapy, which causes death in 4-21% of patients and worsens the quality of life of patients. As a simple and accurate way of identifying patients who are at risk of FN, a lymphocyte count on post-chemotherapy day 5 was suggested. To confirm the feasibility of this method and to define the incidence of FN among our own patient group, we conducted this prospective study. From September 2001 to February 2002, patients who received cytotoxic chemotherapy at Guro Hospital, Korea University, were enrolled. Blood sampling for a complete blood count was done on the starting day of chemotherapy and on day 3 and day 5 post-chemotherapy. The prospective results of the CBC were compared between the FN group and non-FN group. During the study period, 82 patients were enrolled. The male to female ratio was 52:30, and the median age was 56 years old (range: 14-78). Underlying malignancies were non-Hodgkin's lymphoma (14 patients), stomach cancer (17), breast cancer (11), NSCLC (7), hepatobiliary cancer (10), sarcoma (3), colorectal cancer (3), and others (17). The incidence of FN was 18% (15/82 patients), and ANC at the time of FN was 275 ± 327/μl. Duration of fever was 3.9 ± 3.5 days. The incidence of FN was significantly higher in patients with lymphocyte counts at day 3 ≤ 500/μl (P = 0.06), day 5 ≤ 500/μl (P = 0.023), day 3 ≤ 700/μl (P = 0.01), and day 5 ≤ 700/μl (P = 0.0001). As a result of a logistic regression test, a day-5 lymphocyte count ≤ 700/μl was identified as an independent risk factor for FN. In conclusion, a day-5 lymphocyte count <700/μl was a risk factor for FN. To strengthen our result, we are planning to validate in a larger patient group.