Impact of D-index and L-index on pulmonary infection in induction chemotherapy for acute lymphoblastic leukemia and lymphoblastic lymphoma

Objectives: The D-index and the L-index, calculated as the area over the neutrophil and lymphocyte curves, respectively, reflect both the intensity and duration of cytopenia. We, retrospectively, investigated the impact of these indexes on pulmonary infection (PI) in induction chemotherapy for acute lymphoblastic leukemia (ALL) and lymphoblastic lymphoma (LBL). Methods: We included 92 patients (ALL 83, LBL 9) from two institutions. We calculated the D-index and cumulative D-index until the development of PI (c-D-index), which enables real-time risk assessment for infection. We also calculated the L-index (35), defined as the area over the lymphocyte curve during lymphopenia (<700/μl) until day 35 and the cumulative-L-index until the development of PI (c-L-index). Results: Eight patients developed PI on day 20 (median). Two patients were strongly suspected to have bacterial pneumonia, and the others were suspected to have pulmonary fungal infection. The D-index and the L-index (35) in patients with PI were higher than those in patients without PI (7230 ± 4734 vs. 4519 ± 3416, P = 0.041 and 15 458 ± 5243 vs. 8920 ± 5901, P = 0.018), while the c-D-index and the c-L-index were not significantly different. Although the c-L-index did not have predictive value for PI, c-D-index, when treated as a dichotomous variable with a cutoff value of 5589 as determined by a receiver operating characteristic curve analysis, showed a significant difference between two groups (P = 0.045). This association became clearer when we focused on suspected pulmonary fungal infection. Discussion and conclusion: In induction chemotherapy for ALL/LBL, c-D-index with a cutoff value of 5589 might have predictive value for the development of PI.