Provided are a primer for qRT-PCR capable of detecting a circulating cancer cell-based EML4-ALK gene mutation with a detection limit more sensitive than that of the conventional method. According to another embodiment of the present invention, the EML4-ALK gene mutation is detected using circulating lung cancer cells even in a lung cancer patient who cannot perform the ALK-FISH test due to difficulty in collecting a solid biopsy of the lung cancer tissue. It is possible, which provides a method for screening lung cancer patients as to whether antineoplastic agents targeting the EML4-ALK gene mutation can be applied to lung cancer patients. [Selection diagram] Fig. 7血中循環癌細胞ベースのＥＭＬ４－ＡＬＫ遺伝子変異を、従来の方法よりもさらに敏感な検出限界で検出できるｑＲＴ－ＰＣＲ用プライマーを提供する。本発明の他の一実施例によれば、肺癌組織の固体生検採取が困難でＡＬＫ－ＦＩＳＨ検査が実施できなかった肺癌患者でも、血中循環肺癌細胞を用いてＥＭＬ４－ＡＬＫ遺伝子変異を検出可能であり、これによりＥＭＬ４－ＡＬＫ遺伝子変異を標的とする抗癌剤を肺癌患者に適用できるかどうかについての肺癌患者スクリーニング方法を提供する。【選択図】 図７
