A method for aiding in categorising or determining prognosis in a patient with cancer, for example breast cancer (or, for example, hepatocellular, bladder or gastric cancer) or in selecting a therapeutic strategy for a patient with cancer, for example breast cancer (or, for example, hepatocellular, bladder or gastric cancer), the method comprising the step of assessing the level of LMTK3 nucleic acid, protein or activity in a sample obtained from the patient and/or assessing the patient's genotype for LMTK3, optionally at position rs8108419 (in intron 2 of the LMTK3 gene) and/or position rs9989661 (in intron 15 of the LMTK3 gene). The method may further comprise the step of assessing the level of ERα nucleic acid, protein or activity in a sample obtained from the patient, particularly in the case of breast cancer. If the level of LMTK3 nucleic acid, protein or activity in the sample is an elevated level and/or the genotype is LMTK3 rs8108419AA or LMTK3 rs9989661 CT or CC then the selected treatment regime may be an aggressive treatment regime or may comprise treating the patient with an inhibitor of LMTK3 activity and/or an inhibitor of FoxO3a activity. If the level of LMTK3 nucleic acid, protein or activity in the sample is not elevated and/or the genotype is LMTK3 rs8108419GA or GG or LMTK3 rs9989661 TT then the selected treatment regime may be a less aggressive treatment regime.A method for treating a patient with cancer, for example breast cancer (or, for example, hepatocellular, bladder or gastric cancer) or for inhibiting cancer, for example breast cancer (or, for example, hepatocellular, bladder or gastric cancer) cell proliferation in a patient with cancer, for example breast cancer (or, for example, hepatocellular, bladder or gastric cancer), the method comprising administering an inhibitor of LMTK3 activity to the patient. The patient may be a patient in which the level of LMTK3 nucleic acid or protein in a sample from the patient has been determined to be
