Disclosed herein are methods of treating a subject with an estrogen receptor-positive (ER+) breast cancer comprising obtaining a sample of the breast cancer from the subject; determining a level of E-cadherin in the sample is reduced compared to a control; and administering a therapeutically effective amount of an IGF1R pathway inhibitor and an endocrine therapeutic. Also disclosed herein are methods to treat a cancer in a subject comprising administering a therapeutically effective amount of an IGF1R pathway inhibitor and an E-cadherin inhibitor. Also disclosed are methods to predict the likelihood a subject with a breast cancer will respond therapeutically to a treatment comprising administering an IGF1R pathway inhibitor, the method comprising obtaining a sample of the cancer from the subject; and determining a level of E-cadherin in the sample.