Diagnosis of transition zone prostate cancer by multiparametric MRI: added value of MR spectroscopic imaging with sLASER volume selection

Abstract

Background Current multiparametric MRI (mp-MRI) in routine clinical practice has poor-to-moderate diagnostic performance for transition zone prostate cancer. The aim of this study was to evaluate the potential diagnostic performance of novel 1H magnetic resonance spectroscopic imaging (MRSI) using a semi-localized adiabatic selective refocusing (sLASER) sequence with gradient offset independent adiabaticity (GOIA) pulses in addition to the routine mp-MRI, including T2-weighted imaging (T2WI), diffusion-weighted imaging (DWI) and quantitative dynamic contrast enhancement (DCE) for transition zone prostate cancer detection, localization and grading. Methods Forty-one transition zone prostate cancer patients underwent mp-MRI with an external phased-array coil. Normal and cancer regions were delineated by two radiologists and divided into low-risk, intermediate-risk, and high-risk categories based on TRUS guided biopsy results. Support vector machine models were built using different clinically applicable combinations of T2WI, DWI, DCE, and MRSI. The diagnostic performance of each model in cancer detection was evaluated using the area under curve (AUC) of the receiver operating characteristic diagram. Then accuracy, sensitivity and specificity of each model were calculated. Furthermore, the correlation of mp-MRI parameters with low-risk, intermediate-risk and high-risk cancers were calculated using the Spearman correlation coefficient. Results The addition of MRSI to T2WI + DWI and T2WI + DWI + DCE improved the accuracy, sensitivity and specificity for cancer detection. The best performance was achieved with T2WI + DWI + MRSI where the addition of MRSI improved the AUC, accuracy, sensitivity and specificity from 0.86 to 0.99, 0.83 to 0.96, 0.80 to 0.95, and 0.85 to 0.97 respectively. The (choline + spermine + creatine)/citrate ratio of MRSI showed the highest correlation with cancer risk groups (r = 0.64, p < 0.01). Conclusion The inclusion of GOIA-sLASER MRSI into conventional mp-MRI significantly improves the diagnostic accuracy of the detection and aggressiveness assessment of transition zone prostate cancer.

Developments in proton MR spectroscopic imaging of prostate cancer

“…The loss in SNR by performing MRSI at 3T with a phased array coil combination instead of an ERC can be mitigated using LASER type of acquisition sequences [ 17 , 28 , 96 ]. Several studies have demonstrated that in this way MRSI of the prostate can be performed reliably within acceptable time in clinical routine [ 28 , 82 , 106 , 111 ].…”

“…The MR investigations were performed at 3 T with a phased array coil for signal reception. For details see [ 111 ]. A Transversal T2 w MRI shows at least two locations with low signal intensity suspicious for cancer in the left and right side of the transition zone (TZ) of the prostate (white arrows).…”

“…In recent studies, it was demonstrated that employing a GOIA-sLASER sequence at TE=88 ms and only a phase array coil for acquisition and using a support vector machine model analyzing several metabolite ratios, it is possible to discriminate tumor lesions, of low up to high GS, from normal prostate tissue in the transition zone with high accuracies of 96% [ 82 ]. Even better results were obtained in an mpMRI exam, in which MRSI was combined with T2 weighted and diffusion weighted MRI [ 111 ]. The complementary role of MRSI in tumor localization by mpMRI is illustrated by the case shown in Fig.…”

“…By adding MRI and MRSI measures to a clinical nomogram, it was possible to identify significant cancer at an AUC of 0.85 [ 195 ]. In a study using a GOIA-sLASER sequence at 3T with TE=88ms to measure metabolites and a support vector machine analysis it was possible to separate low risk cancer lesions from high risk in the transition zone in a combination of ADC, Ktrans and metabolite ratios at an AUC of 0.86, while AUC was only 0.64 if ADC was combined with Ktrans [ 111 ].…”

Multiple metabolic pathways fuel the truncated tricarboxylic acid cycle of the prostate to sustain constant citrate production and secretion

“…This loss of the citrate-secretory phenotype occurs in virtually all PCa cases, highlighting it as a hallmark of PCa [ [1] , [2] , [3] , [4] , [8] , [9] , [10] , [11] , [12] , [13] , [14] , [15] ]. Accordingly, decreases in prostate citrate levels can be detected using magnetic resonance spectroscopy, and several studies have identified this decrease in citrate as a biomarker for PCa diagnosis [ [16] , [17] , [18] ]. Moreover, lower intratumor citrate concentrations have been associated with shorter recurrence-free survival, suggesting that reprogramming of citrate is not only linked to carcinogenesis but also to PCa progression [ 19 , 20 ].…”