The disclosure provides a method of immunotherapy for a cancer patient, comprises administering vaccines against Globo series antigens (i.e., Globo H, Stage-specific embryonic antigen 3 “SSEA3” and Stage-specific embryonic antigen 4 “SSEA4”). Specifically, the method comprises administering Globo H-KLH (OBI-822) in patients with Metastatic Breast Cancer. The disclosure also provides a method of comprises selecting a cancer patient who is suitable as treatment candidate for immunotherapy. In addition, the disclosure provides therapeutic agents, including monoclonal antibodies (mAbs) that bind specifically to Globo series antigens and related biomarkers useful in focusing such therapeutic and diagnostic regimens.