Thus, in order to develop a method for analysing the EGFR gene status in large numbers of patients and applying the results to decide whether gefitinib treatment is indicated, we performed a feasibility study to clarify whether the LH-MSA using small numbers of cancer cells could be applied for analysis of EGFR mutations, and then further evaluated its prediction ability of the EGFR gene mutation status relative to the gefitinib response. The gene discussed is EGFR; the disease is cancer.