RFLP Found EGFR Mutations Quickly in NSCLC Patients Treated With Gefitinib

September 1, 2005

This supplement to Oncology News International includes more than 15 reportson presentations made at the 41st annual meeting of the American Society of Clinical Oncology.Reviews focus on the use of targeted agents in non–small-cell lung cancer and other solid tumors,evaluating the novel therapies bevacizumab, cetuximab, bortezomib, erlotinib, and gefitinib, aloneand/or in combination with other chemotherapy agents. Continuing medical education credit isavailable by completing a post-test and evaluation online at www.cancernetwork.com/cme.

TOKYO, Japan-Using restrictionfraction length polymorphisms(RFLP) looks promising as aquick and cost-effective method ofscreening tumor specimens for epidermalgrowth factor receptor (EGFR)mutations, say researchers who comparedthis method with direct sequencing.RFLP identified the same mutationsas direct sequencing in 73 tissuesamples, said Ichiro Kawada, MD, ofthe Keio University School of Medicinein Tokyo, who presented the findings(abstract 7071)."This was basically a methodologicstudy sending the message that thereare other ways besides sequencing toquickly measure the presence of EGFRmutations," said Roman Perez-Soler,MD, chief of the oncology division atMontefiore Medical Center in NewYork, in discussing the trial.Direct sequencing, currently theonly method used to verify existenceof EGFR mutations, is time-consum-ing and expensive, the investigatorspointed out. Now that EGFR mutationshave been linked to response totyrosine kinase inhibitors in lungcancer, screening for mutations isemerging as an important step inselecting treatment and in clinical trialprotocols.To use RFLP, the investigators firstextracted RNA from tumor specimensof 73 patients with non-small-cell lungcancer (NSCLC) who had been treatedwith gefitinib. They then madecDNA, then performed PCR on thecDNA using three pairs of originalprimers designed for RFLP to detectmutations. The PCR products weredigested with corresponding enzymes.Before and after digestion, the PCRproducts were run on a 2% agarose geland the existence of mutations wasassessed. All specimens were also directlysequenced before digestion toidentify mutations.Both RFLP and direct sequencingfound the same mutations: 19% ofspecimens had deletion mutations inexon 19; 11% had point mutations inexon 21, codon 858; and 1% had pointmutations in exon 18, codon 719.The researchers also found that themutations were closely associated withresponse to gefitinib. Eight of the ninepatients who responded had mutationsand none of those who did notrespond had mutations. Dr. Kawadaand colleagues concluded that RFLPdetectedmutations may be useful inpredicting the sensitivity of NSCLCpatients to gefitinib.