Absolute lymphocyte count (ALC) as predictor of Pneumocystis Jiroveci Pneumonia (PCP) infection in patients on immune checkpoint inhibitors (ICPi).

Abstract

e14255 Background: Checkpoint inhibitor pneumonitis (CIP) is an uncommon but serious immune related adverse event needing treatment with prolonged steroids. PCP prophylaxis is recommended for patients on daily prednisone equivalents of 20 mg or greater for at least 1 month. Known risk factors for PCP infection in general population are glucocorticoid use and defects in cell-mediated immunity. We conducted a retrospective study to evaluate the association between ALC and development PCP infection in the patients with CIP treated with steroids. Methods: A retrospective analysis of subjects who received ICPi for any type of cancer from 2011 to 2018 at a single institution was conducted. PCP was diagnosed by PCR of bronchioalveolar lavage. In patients with CIP, ALC at the beginning of steroid treatment, dose and duration of steroids and development of PCP infection was recorded. The median ALC was compared between the patients with PCP infection and without PCP infection via Welch’s t- test at 5% alpha. Results: Out of 515 patients who received ICPi, there were 429 (83.3%) Caucasians, 79(15.3%) African Americans, 7(1.3%) others. CIP developed in 23 (4.38 %) patients. There were 15(65%) males, 8 females (35%), 20(86.9%) Caucasians and 2(8.6%) African Americans. Median age was 67 Yrs. (range 29-80). Six out of 23 (26%) patients with CIP developed PCP infection. Median ALC in the patients with PCP infection was 0.75 K/uL (range 0.2-0.83) compared to 1.14 K/uL (range 0.18 - 1.76) in those without PCP infection (p = 0.0182). Conclusions: In patients with CIP, low ALC and prolonged steroid therapy are more likely to result in PCP infection as opposed to steroid therapy alone. Low ALC and prolonged steroid therapy may select patients who require PCP prophylaxis. [Table: see text]