As we known, many compounds in the human body contain phosphorus which provides vital information on changes in cancer microenvironment. Phosphorous-31 (31P) magnetic resonance spectroscopy (MRS), as a powerful non-invasive tool, can be utilized in diagnosing cancer and monitoring their response to therapy. Thus, it is expected to enable doctors to improve the treatment through personalizing therapy and reducing side effects. This paper presents a review of 31P-MRS as a non-invasive tool to assess unique relevant biomarkers from cancer in patients in vivo clinically.