Identification of Prognostic Markers in Bone Sarcomas Using Proton-Decoupled Phosphorus Magnetic Resonance Spectroscopy

It has been hypothesized that the ³¹Phosphorus (³¹P) nuclear magnetic resonance spectrum from certain tumors may provide prognostic information. The goal of the present study was to identify prognostic metabolic markers by using proton-decoupled phosphorus magnetic resonance spectroscopic imaging (³¹P MRSI). Twenty patients with bone [osteogenic (OS) and Ewing's (ES) and/or primitive neuroectodermal tumor (PNET)] sarcoma, treated with chemotherapy and surgery or with chemotherapy alone, underwent ³¹P MRSI studies pre- and post-therapy. The studies were performed on a 1.5 Tesla General Electric (GE) clinical scanner equipped with a stand-alone proton decoupler and a dual ¹H/³¹P surface coil pair. The limited sensitivity of the 31p nucleus required that a large soft tissue component of the disease be located within 10 cm (maximum distance) of the body surface and the use of a highly sensitive coil placed near the skin surface. Proton decoupling and nuclear Overhauser enhancement were used to improve the spectral resolution and signal:noise ratio. Baseline ³¹P spectral features and metabolic changes with treatment were compared with treatment outcome. The patients were categorized depending on survival as event-free survivors or those who died. The pretreatment nucleoside triphosphate:inorganic phosphate (NTP:P_i) ratio, an index of tumor bioenergetic status, was significant (P = 0.003) in differentiating event-free survivors versus those who died. The pretreatment NTP:P_i was higher in patients who were destined to undergo a durable event-free survival compared with those who died. The results are promising, although a prospective study is necessary for confirmation. ³¹P MRSI appears to be a useful tool for the prediction of survival before therapy in bone sarcomas.