Successful treatment with erlotinib of severe neutropenia induced by gefitinib in a patient with advanced non-small cell lung cancer.

Neutropenia is a rare side effect of gefitinib and was scarcely reported in many large-scale randomized phase III trials using gefitinib monotherapy as first-line treatment. A 77-year-old female was referred to our institution due to abnormal shadow of the right lung, diagnosed by CT scan and biopsy histopathology as adenocarcinoma of the lung (cT3N1M1b). Mutation analysis with PCR-Invader assay of tumor DNA samples revealed short in-frame deletion in exon 19. Based on the diagnosis, first-line treatment was initiated using oral gefitinib (250 mg, daily). During the initial 27 days of gefitinib therapy, the only side effect was a mild skin rash. After 28 days, there was marked tumor shrinkage, indicative of a partial response to gefitinib; however, grade 4 neutropenia was also detected. The patient was switched to the oral erlotinib monotherapy (150 mg/day) as second-line chemotherapy with careful monitoring of neutropenia. Discontinuation of the gefitinib, without the need for granulocyte colony-stimulating factor support, was successful in allowing the neutrophils and leukocytes counts to recover to normal by day 47. The patient continued oral erlotinib for more than 9 months and there has been no evidence of neutropenia, leukopenia, or disease progression. Clinicians should be aware that gefitinib-induced neutropenia in patients with non-small cell lung cancer can be treated successful by switching to erlotinib.