Erlotinib resistance is altered after gemcitabine chemotherapy for recurrent non-small-cell lung cancer.

We report the case of a male Mongolian lifelong non-smoker with recurrent non-small-cell lung cancer (NSCLC) who developed resistance to the epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor erlotinib after initially responding to this agent but then subsequently had another response to a second course of erlotinib treatment after intervening gemcitabine chemotherapy. Sixteen months after the patient received chemoradiotherapy with gemcitabine/cisplatin plus radiotherapy, his recurrent mediastinal metastases were found to have progressed. Treatment with erlotinib was followed by an initial, partial response but evidence of progression was again observed 6 months later. The patient was then treated with gemcitabine chemotherapy, which resulted in a reduction in tumour volume. One month later, progression of mediastinal metastases was again observed and the patient received a second course of erlotinib. Another partial response occurred and the patient's disease remained stable at the 9-month follow-up visit (and with no reported symptom progression at an 11-month telephone follow-up). Genetic examination of tumour tissue collected at the time of the original diagnosis and during the second course of erlotinib therapy revealed activating exon 19 mutation in the EGFR gene. This case suggests that resistance to erlotinib may change following chemotherapy and that repeat erlotinib therapy may be worth considering after chemotherapy in NSCLC patients who initially respond positively to erlotinib treatment but subsequently experience recurrence of disease.