First Line Gefitinib by FDG-PET Metabolic Response

Gefitinib has anti-tumor activity as a result of EGFR tyrosine kinase inhibition, reducing multiple downstream signaling processes that activate cell proliferation and other cell responses, including cell migration angiogenesis, and reduced apoptosis. Recently, it has been approved for the first line treatment of advanced NSCLC that harbors EGFR mutation. In IPASS trial, tumors with EGFR mutation produced 71.2% of clinical response to first line gefitinib while tumors with wild type EGFR showed only 1.1% of response. Therefore, patient selection is critical for the clinical use of EGFR tyrosine kinase inhibitors as first line treatment. When considering 1st line gefitinib treatment for NSCLC, we need EGFR mutational status of the tumor. But most patients do not give us such information at the time of diagnosis, because it requires tumor tissue and some time period for EGFR examination. So, we need other strategies such as using PET scan for early prediction of response to gefitinib. Glucose metabolic activity closely reflects responses to gefitinib therapy. In preclinical study with gefitinib sensitive cell lines, there was a dramatic decrease in FDG uptake as early as 2 hours after treatment. And these metabolic alterations preceded changes in cell cycle distribution, thymidine uptake and apoptosis. In contrast, gefitinib resistant cells exhibited no measurable changes in FDG uptake, either in cell culture or in vivo. The strategy using FDG-PET may guide us to perform 1st line geftinib. Recently investigators reported that FLT-PET or FDG-PET could predict response to EGFR tyrosine kinase (TKI) early after 1 week of treatment. And % decrease more than 20% of maximum SUV of main lesion after 1 week of EGFR TKI treatment could predict response to that drug. More than 20% decrease of SUV is a significant change during reproducibility test and also considered as a criteria for response prediction of paclitaxel/cisplatin chemotherapy. So, investigators develop a protocol of 1st line gefitinib treatment for NSCLC according to FDG-PET response. And if the patient showed less than 20% decrease of peak SUV, investigators will stop gefitinib and treat him or her with the regimen of pemetrexed/cisplatin.