Disclosed is a method for determining the efficacy of GPC3-targeted therapeutic agent therapy for a patient or against a cancer in the patient, prior to receiving GPC3-targeted therapeutic agent therapy, or for determining whether to continue GPC3-targeted therapeutic agent therapy for a patient, wherein the method includes a step of monitoring the free GPC3 concentration in a biological specimen isolated from a patient prior to receiving GPC3-targeted therapeutic agent therapy and/or a patient having received GPC3-targeted therapeutic agent therapy, and determining the GPC3-targeted therapeutic agent therapy to be effective, or determining to continue the GPC3-targeted therapeutic agent therapy, when the free GPC3 concentration is a predetermined value. Also disclosed is a GPC3-targeted therapeutic agent or drug formulation for further administration to a patent for whom GPC3-targeted therapeutic agent therapy has been determined effective, or for whom it has been determined to continue GPC3-targeted therapeutic agent therapy.本發明係揭示決定GPC3標的治療劑療法對接受GPC3標的治療劑療法之前的患者或患者中之癌之有效性、或決定對患者繼續進行GPC3標的治療劑療法之方法，其係包含監測接受GPC3標的治療劑療法之前的患者及/或自接受過GPC3標的治療劑療法之患者中所單離之生物學試樣中的游離GPC3濃度，該游離GPC3濃度為特定值時，則決定該GPC3標的治療劑療法為有效、或決定繼續進行該GPC3標的治療劑療法之方法。又，亦揭示用以對已決定GPC3標的治療劑療法為有效、或已決定繼續進行GPC3標的治療劑療法之患者進一步投與之GPC3標的治療劑或製劑。
