A method (i) of identifying subjects with HER2 positive cancer that should be screened for brain metastasis; (ii) of identifying subjects with HER2 positive cancer that should receive treatment with a HER2-acting agent and a second form of cancer treatment; (iii) for determining an expected time to brain metastasis (TTBM) in a subject with a HER2-positive cancer; (iv) for determining the relative likelihood of whether a subject with a HER2-positive cancer is at risk for developing brain metastases; and/or (v) of determining if a subject with HER2 positive cancer is within in a subset of HER2 positive cancer subjects that should be screened for brain metastasis, comprising: (a) providing a biological sample of a tumor obtained from the subject's cancer; (b) measuring the amount of HER2 in the biological sample; (c) determining whether the amount of HER2 protein in the subject's sample is above a HER2 cutoff, wherein the cutoff has been determined based on the measurement of the amount of HER2 protein in biological samples of a subject population and the cutoff divides the samples of the subject population into two distinct patient subgroups; and (d) (i) indicating that the subject should be screened for brain metastasis if the amount of HER2 protein is above the HER2 cutoff; (ii) indicating that the subject should receive treatment with a HER2-acting agent and a second form of cancer treatment if the amount of HER2 protein is above the HER2 cutoff; (iii) indicating the subject's expected TTBM based on the incidence of brain metastasis over time in a reference population having HER2 protein levels above or below the HER2 cutoff; (iv) indicating that, if the amount of HER2 protein in the biological sample is above the HER2 cutoff, the subject is more likely to be at risk for developing brain metastases; and/or (v) indicating that the subject should be screened for brain metastasis if the amount of HER2 protein is above the HER2 cutoff. (a) providing a biological sample of a tumor obtained from the subject's cancer; (b) measuring the amount of HER2 in the biological sample; (c) determining whether the amount of HER2 protein in the subject's sample is above a HER2 cutoff, wherein the cutoff has been determined based on the measurement of the amount of HER2 protein in biological samples of a subject population and the cutoff divides the samples of the subject population into two distinct patient subgroups; and (d) (i) indicating that the subject should be screened for brain metastasis if the amount of HER2 protein is above the HER2 cutoff; (ii) indicating that the subject should receive treatment with a HER2-acting agent and a second form of cancer treatment if the amount of HER2 protein is above the HER2 cutoff; (iii) indicating the subject's expected TTBM based on the incidence of brain metastasis over time in a reference population having HER2 protein levels above or below the HER2 cutoff; (iv) indicating that, if the amount of HER2 protein in the biological sample is above the HER2 cutoff, the subject is more likely to be at risk for developing brain metastases; and/or (v) indicating that the subject should be screened for brain metastasis if the amount of HER2 protein is above the HER2 cutoff. (ii) indicating that the subject should receive treatment with a HER2-acting agent and a second form of cancer treatment if the amount of HER2 protein is above the HER2 cutoff; (iii) indicating the subject's expected TTBM based on the incidence of brain metastasis over time in a reference population having HER2 protein levels above or below the HER2 cutoff; (iv) indicating that, if the amount of HER2 protein in the biological sample is above the HER2 cutoff, the subject is more likely to be at risk for developing brain metastases; and/or (v) indicating that the subject should be screened for brain metastasis if the amount of HER2 protein is above the HER2 cutoff.