Patients with stage IV breast, colorectal, or non-small cell lung cancer (NSCLC) who will get bevacizumab as a standard of care, as well as patients with breast, colorectal, ovarian/fallopian tube/peritoneal, head and neck, or NSCLC cancer about to initiate bevacizumab. Where possible, the study population will include a control group not receiving bevacizumab.