Abstract
BACKGROUND AND OBJECTIVE: Pemetrexed and epidermal growth factor receptor (EGFR)-tyrosine kinase inhibitors (TKIs) were used in patients with EGFR mutation to determine their effects. This study analyzed the influence of EGFR-TKIs on pemetrexed by observing the clinical efficacy and toxicity of pemetrexed following responses to EGFR-TKIs. METHODS: Pulmonary adenocarcinoma patients were divided into EGFR-TKIs and no-EGFR-TKI groups according to the targeted therapy. All patients received pemetrexed (500 mg/m2) as second (or higher)-line treatment. The Response Evaluation Criteria in Solid Tumors (version 1.0) were used to evaluate the response to pemetrexed. Adverse events were classified based on version 4.0 of the National Cancer Institute Common Toxicity Criteria. RESULTS: There were 57 patients in the EGFR-TKIs group and 56 in the no-EGFR-TKIs group. The disease control rates (DCRs) were 77.2% and 67.9% (P=0.367). The progression free survival (PFS) periods were 5.95 and 3.55 months (P=0.535). The overall survival (OS) periods were 10.10 and 8.24 months (P=0.432). However, these values were not statistically significant. The common toxicities of pemetrexed were hematologic and gastrointestinal (grades I and II). Two patients in the EGFR-TKIs group discontinued pemetrexed because of severe toxicities, which were not observed in the no-EGFR-TKIs group. Both groups had one patient who reduced dosage because of myelosuppression (grade IV). There were five and nine patients in the EGFR-TKIs and no-EGFR-TKIs groups, respectively, who delayed therapy not because of severe toxicities but due to subjective factors. CONCLUSION: The DCRs, PFS periods, and OS periods of the patients administered with pemetrexed following EGFR-TKIs were better than those of the EGFR-TKIs group, but the differences were not statistically significant. Therefore, sequential pemetrexed administration caused negligible toxicities and can be used in adenocarcinoma therapy following responses to EGFR-TKIs.