One of the emerging techniques in prostate cancer imaging is magnetic resonance spectroscopy (MRS), which provides bio-chemical information from body tissue in a safe and noninvasive method. In the presence of an applied external magnetic field, the atomic nuclei within molecules behave like tiny magnets and resonate at different frequencies at the same magnetic field strength. This is the basic principle of magnetic resonance imaging (MRI) and spectroscopy (1-4).

MRS displayed the relative concentrations of key chemical constituents, i.e. Citrate, choline, and creatinine, of the cellular metabolites within the prostate gland. High levels of choline and decreased levels of citrate indicates the presence of cancer cells, thus it can be used to help in the estimation of tumor volume, extracapsular extension and post-radiotherapy recurrence (5).

What other scientists say

California, USA – 2004, Pickett et al characterized the metabolic response in the prostate and tried to find a correlation between MRI with MRS imaging through biopsy findings, and serum prostate-specific antigen (PSA) level after external beam radiotherapy. “The results of this study suggest that when used in conjunction with PSA determination and biopsy, MRS imaging may provide a greater level of confidence when assessing local control.” They also added that "MRS imaging could also help distinguish the benign blip from local recurrence after EBRT and be useful in evaluating the complex relationships between treatment and the time to the indication of successful therapy, but longer follow-up is required to confirm these initial observations.”

Mexico – 2005, Averna et al investigated NMR spectroscopy of unprocessed human seminal plasmas. They concluded that high resolution 1H nuclear MRS can be used to measure citrate in seminal fluid, and providing a new, rapid, and noninvasive screening method.

France - Another study is published in the same year evaluating the use of combined MRI and MRS imaging with their previous patients from April 2003 to April 2004. Amsellem-Ouazana et al stated that “This preliminary study shows that the combination of MRI and MRSI might be able to guide and therefore limit the number of iterative biopsies and cores for patients who are at high risk of having a prostate cancer. In some cases, MRS imaging alone allows identification of neoplasic prostatic zones.”

Mexico - 2006, Kline et al compared the performance of citrate concentration measurements in unprocessed human semen and expressed prostatic secretions from controls and from patients with biopsy confirmed prostate cancer to that of prostate specific antigen testing with respect to specificity and sensitivity for prostate cancer detection. They found out that “In vitro nuclear magnetic resonance spectroscopic measurement of the citrate concentration in semen or expressed prostatic secretions outperforms prostate specific antigen testing for detecting prostate cancer.”

Germany - 2007, Mueller&Scherr summarized the current technical and biochemical aspects, and clinical application of proton MRS of the human prostate in vivo. They reported that combined MRI and 3D-MRS imaging of the prostate is suitable for planning of biopsy and therapy, and to post-therapeutic follow-up. Notwithstanding their result, for broad clinical acceptance they recommended to facilitate MRS examinations and their evaluation and make MRS available to a wider range of institutions.

Italy – Another study to assess the accuracy of MRS imaging (1H-MRSI) and dynamic contrast-enhanced MR (DCEMR) in the depiction of local prostate cancer recurrence in patients with biochemical progression after radical prostatectomy (RP) is done by Sciarra et al (2007). The results showed that combined 1H-MRS imaging and DCDMR is an accurate method to identify local prostate cancer recurrence in patients with biochemical progression after RP.

Switzerland&California, USA – 2008, a systematic review to meta-analyse the diagnostic accuracy of combined MRI/MRS imaging in prostate cancer and to explore risk profiles with highest benefit is done by Umbehr et al. They pointed out that "a limited number of small studies suggest that MRI combined with MRS imaging could be a rule-in test for low-risk patients. This finding needs further confirmation in larger studies and cost-effectiveness needs to be established.”

New York, USA - 2009, Brame et al published a clinical investigation to quantify the probability that a cancer-suspected lesion has an elevated Gleason grade as a function of average MRS score and tumor volume. They reported that “In patients with biopsy Gleason score ≥4+3, high MRS imaging tumor volume and (creatine + choline)/citrate ratio may justify the initiation of voxel-specific dose escalation.”

California, USA - A study to evaluate whether pretreatment combined endorectal MRI and MRS imaging findings are predictive of outcomes in patients who undergo external beam radiotherapy for prostate cancer is also published recently. Joseph et al reported that “In multivariate analysis, MRI and MRS imaging findings before EBRT in patients with prostate cancer are more accurate independent predictors of outcome than clinical variables, and in particular, the findings of seminal vesicle invasion and extensive tumor predict a worse prognosis.”

In summary, recent studies mentioned above showed that Magnetic Resonance Imaging and spectroscopy is a useful tool to diagnose Prostate cancer. In most cases, the combination of MRI and MRS yields superior diagnostic results than either modality alone (15).



References

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5. Ravizzini G, Turkbey B, Kurdziel K, et al. New horizons in prostate cancer imaging. European Journal of Radiology 2009; 70:212-226.

6. Pickett B, Kurhanewicz J, Coakley F, et al. Use of MRI and spectroscopy in evaluation of External beam radiotherapy for prostate cancer. International Journal of Radiation Oncology Biology Physics 2004; 60(4): 1047-1055.

7. Averna T, Kline E, Smith A, et al. A decrese in 1H nuclear magnetic resonance spectroscopically determined citrate in human seminal fluid accompanies the development of prostate adenocarcinoma. The Journal of Urology 2005; 173(2): 433-438.

8. Amsellem-Ouazana D, Younes P, Conquy S, et al. Negative prostatic biopsies in patients with a high risk of prostate cancer: Is the combination of endorectal MRI and Magnetic Resonance Spectroscopy Imaging (MRSI) a Useful Tool? A Preliminary Study. European Urology 2005; 47(5): 582-586.

9. Kline E, Treat E, Averna T, et al. Citrate Concentrations in Human Seminal Fluid and Expressed Prostatic Fluid Determined via 1H Nuclear Magnetic Resonance Spectroscopy Outperform Prostate Specific Antigen in Prostate Cancer Detection. The Journal of Urology 2006; 176(5): 2274-2279.

10. Mueller-Lisse U, Scherr M. Proton MR spectroscopy of the prostate. European Journal of
Radiology 2007; 63(3): 351-360.

11. Sciarra A, Panebianco V, Salciccia S, et al. Role of Dynamic Contrast-Enhanced Magnetic Resonance (MR) Imaging and Proton MR Spectroscopic Imaging in the Detection of Local Recurrence after Radical Prostatectomy for Prostate Cancer. European Urology 2007;
54(3): 589-600.

12. Umbehr M, Bachmann L, Held U, et al. Combined Magnetic Resonance Imaging and Magnetic Resonance Spectroscopy Imaging in the Diagnosis of Prostate Cancer: A Systematic Review and
Meta-analysis. European Urology 2008; 55(3): 575-591.

13. Joseph T, McKenna D, Westphalen A, et al. Pretreatment Endorectal Magnetic Resonance Imaging and Magnetic Resonance Spectroscopic Imaging Features of Prostate Cancer as Predictors of Response to External Beam Radiotherapy. International Journal of Radiation Oncology Biology Physics 2009; 73(3):665-671.

14. Brame R, Zaider M, Zakian K, et al. Regarding the focal treatment of prostate cancer: Inference of the Gleason grade from magnetic resonance spectroscopic imaging. International Journal of Radiation Oncology Biology Physics 2009; 74(1): 110-114.

15. Villeirs G, Oosterlinck W, Vanherreweghe E, et al. A qualitative approach to combined magnetic resonance imaging and spectroscopy in the diagnosis of prostate cancer. European Journal of Radiology, In Press, Corrected Proof, Available online 11 December 2008.