Hyperpolarized 1-13C-2-oxoglutarate as contrast agent in 13C Magnetic Resonance diagnostic technique (13C-MRI) for use in the diagnosis of cancer. In particular, upon administration of said 1-13C-2-oxoglutarate, signals of 1-13C-glutamate are detected. More in particular, different MR signals from 13C nuclei are detected and compared, said comparison being useful to determine a difference between tumor and non-tumor tissues, to determine the aggressiveness of a tumor or the efficacy of an anti-tumor therapy.
