Abstract: The presently disclosed subject matter relates to the use of one or more biomarkers to evaluate whether a PI3K? inhibitor would produce an anti-cancer effect in a subject during the course of treatment with a PI3K? inhibitor. It is based, at least in part, on the discovery that certain nucleotides can be isolated from the serum of patients undergoing cancer treatment and can be used as a biomarker to indicate the effectiveness of PI3K treatment on cancer growth. Accordingly, in a non-limiting embodiment, a method for determining whether an anti-cancer effect is likely being produced in a cancer by a PI3K? inhibitor, comprises determining the presence and/or level of one or more PIK3CA biomarkers in one or more samples serially obtained during PI3K? inhibitor treatment, where if the presence and/or level of a PIK3CA biomarker is increased, it is less likely that the PI3K? inhibitor is having an anti-cancer effect on the cancer.

Abstract: The presently disclosed subject matter relates to the use of one or more biomarkers to evaluate whether a PI3K? inhibitor would produce an anti-cancer effect in a subject during the course of treatment with a PI3K? inhibitor. It is based, at least in part, on the discovery that certain nucleotides can be isolated from the serum of patients undergoing cancer treatment and can be used as a biomarker to indicate the effectiveness of PI3K treatment on cancer growth. Accordingly, in a non-limiting embodiment, a method for determining whether an anti-cancer effect is likely being produced in a cancer by a PI3K? inhibitor, comprises determining the presence and/or level of one or more PIK3CA biomarkers in one or more samples serially obtained during PI3K? inhibitor treatment, where if the presence and/or level of a PIK3CA biomarker is increased, it is less likely that the PI3K? inhibitor is having an anti-cancer effect on the cancer.