SU-E-I-65: Magnetic Resonance Spectroscopy of the Prostate: A Phantom Study of Metabolite Concentrations.

PURPOSE: Magnetic Resonance Spectroscopy (MRS) of the prostate is not used in radiotherapy departments on a regular basis due to a number of issues. The indication and severity of prostate cancer is related to the presence of choline in the prostate, in particular, the ratio of choline (plus creatine) to citrate. In-vivo data supports this theory only marginally but lacks strong correlation with biopsy data. The situation is further complicated by the lack of precise spatial information in biopsy, variation of magnetic susceptibility, and spatial dependence of MRS data on the distance from the endo-rectal coil. The latter also cause low signal-to-noise ratio (SNR). We intend to understand how the level of metabolite concentrations and spatial dependences determine what is observed in MRS. METHODS: A spherical phantom is filled with water solutions containing various amounts of metabolites. It is placed on top of an endo-rectal coil with the balloon filled with per fluorocarbon. MRS data is acquired on a GE 1.5 T MR scanner. The metabolite values, their ratios etc as reported in GE software, FuncTool are studied as functions of metabolite concentrations in the phantom. RESULTS: Analysis of the phantom data indicates that the metabolite ratio reported in FuncTool is approximately linearly correlated to the metabolite concentrations used in the phantom to a certain point and then saturates whereas the largest metabolite value is well correlated with its concentration in the phantom. All metabolite values become weaker and SNR lower as we move away from the coil. CONCLUSIONS: This work indicates the potential of using metabolite values directly provided their spatial dependences on the distance of the voxels from the endo-rectal coil can be accommodated.

Prostate cancer gene therapy and the role of radiation.

Even though prostate cancer is detected earlier than in the pre-PSA era, prostate cancer is the second leading cause of cancer mortality in the American male. Prostate cancer therapy is not ideal, especially for high-risk localized and metastatic cancer; therefore, investigators have sought new therapeutic modalities such as angiogenesis inhibitors, inhibitors of the cell signaling pathway, vaccines, and gene therapy. Gene therapy has emerged as potential therapy for both localized and systemic prostate cancer. Gene therapy has been shown to work supra-additively with radiation in controlling prostate cancer in vivo. With further technological advances in radiation therapy, gene therapy, and the understanding of prostate cancer biology, gene therapy will potentially have an important role in prostate cancer therapy.

Microvessel density in prostate cancer: lack of correlation with tumor grade, pathologic stage, and clinical outcome.

OBJECTIVES: Angiogenesis is believed to play an important role in tumor progression and metastasis. Previous studies have suggested that the microvessel density (MVD) of prostate tumors may be of prognostic value. This study investigated the reliability of assessing MVD in radical prostatectomy specimens and its value as an independent prognostic indicator in men with clinically localized prostate cancer. METHODS: One hundred radical prostatectomy specimens from 1993 to 1995 were randomly selected for this study. Thirteen cases were excluded because the patients had undergone neoadjuvant hormonal therapy or tissue blocks were unavailable. The median follow-up time was 36 months. Tumor blocks were immunostained using the endothelial-specific antibody CD31. MVD was counted in areas with the greatest microvessel immunostaining, which were designated "hot spots." MVD was analyzed for associations with clinical and pathologic factors. In a subset of 60 cases, the same observer repeated the counts three times. RESULTS: Intraobserver reliability for MVD counting was excellent (reliability coefficient 0.82), demonstrating that this method could be reproduced by a single observer. MVD was not associated with Gleason sum, tumor stage, surgical margin status, or seminal vesicle invasion. Of the 87 patients, 20 (23%) had a prostate-specific antigen (PSA) failure during a 36-month median follow-up time. As expected, Gleason sum and tumor stage were strong predictors of PSA failure, with risk ratios of 2.1 and 2.3, respectively. In contrast, MVD was not associated with PSA failure. CONCLUSIONS: MVD, as determined by CD31, can be reliably measured by a single observer, but it is not a useful prognostic indicator for men with clinically localized prostate cancer.