A case with small-cell transformation after treatment with EGFR tyrosine kinase inhibitor for lung adenocarcinoma

Background: Small-cell transformation is a relatively rare cause of acquired resistance after treatment with epidermal growth factor receptor tyrosine kinase inhibitor (EGFR-TKI) for EGFR mutated lung adenocarcinoma. ere we report a case with small-cell transformation after treatment with EGFR-TKI. Case: Eighty-one year-old woman who was diagnosed with advanced lung adenocarcinoma harboring EGFR mutation (exon 19 deletion) had progressed disease after being treated with gefitinib for two years. Because second line treatment with pemetrexed had no effect, bronchoscopic examination was taken place for the purpose of re-biopsy from subcarinal lymph node, which turned out to be small-cell c. As small-cell transformation was highly suspected by immunohistochemical stainings, the patient received CBDCA/VP16 treatment for 2 cycles. Although her symptoms were transiently relieved by the treatment, her performance status declined and CT confirmed disease progression. She chose best supportive care thereafter. Discussion: Small-cell transformation is reported to occur in about 10% of patients whose tumors acquired resistance after EGFR-TKI treatment. Although there is no standard of care for this subset, chemotherapeutic regimen for small cell lung cancer are commonly applied. We will present the molecular pathological profile of this case along with review of the literature.