Tumor-associated eosinophilia in a patient with EGFR-positive, MET-amplified lung adenocarcinoma refractory to targeted therapy: a case report and review of literature.

Paraneoplastic eosinophilia is a rare complication observed in 1% solid tumor cases and appears to have tumor type-dependent prognostic impact, in which the increased eosinophil count was generally associated with unfavorable prognosis. In the English literature, more than 20 patients have been reported of eosinophilia associated with primary non-small cell lung cancer (NSCLC) at diagnosis, all of whom underwent either surgery, chemotherapy, or symptomatic therapy. Herein, we describe clinical course a stage IV NSCLC patient with paraneoplastic eosinophilia and leukocytosis and receiving targeted therapy. A 64-year-old male former smoker was diagnosed with lung adenocarcinoma harboring EGFR L858R mutation and MET amplification. Blood eosinophilia was manifested at diagnosis and confirmed to be paraneoplastic by eliminating other potential causes. The disease progressed rapidly within a month on EGFR inhibitor icotinib and then within three months on icotinib plus crizotinib after rapid response within the first month. A multi-target kinase inhibitor anlotinib was added, and the disease progressed one month later despite initial self-reported asymptomatic high-performance status. The patient was lost to subsequent follow-ups. Radiographic evaluation of disease control or progression coincided with respective distinct alleviation or worsening of eosinophilia. Consistent with previous reports of poor clinical outcome associated with blood eosinophilia, our results suggested a negative prognostic impact in EGFR-/MET-altered NSCLC. This case is, to the best of our knowledge, the first to provide evidence for blood eosinophilia paralleling disease progression in an EGFR- and MET-altered lung adenocarcinoma under targeted therapy, which suggested negative prognostic impact of blood eosinophilia in driver-positive NSCLC.