MRI spectroscopy could predict biochemical relapse after prostatectomy
MedWire News: Preoperative endorectal magnetic resonance spectroscopic imaging (MRSI) could predict whether patients are likely to experience biochemical recurrence (BCR) after radical prostatectomy, say US researchers.
The volume of the index lesion and the presence of high-grade voxels on MRSI correlate with time to BCR independently of clinical data such as stage, grade, and prostate-specific antigen (PSA) levels, report Kristen Zakian (Memorial Sloan-Kettering Cancer Center, New York) and colleagues.
"This indicates that not only the size but the degree of metabolic abnormality in the MRSI lesion is related to BCR risk," they add in the Journal of Urology.
The team investigated the relationship between pre-treatment MRI (magnetic resonance imaging), MRSI, and BCR using imaging data from a cohort of 130 radical prostatectomy patients, with the aim of improving preoperative outcome predictions.
The majority (69.2%) of the cohort had a pre-treatment MRI recurrence risk score of 2 (out of 7), indicating visible tumor but no extracapsular extension of disease, and after a median 68-month follow-up from surgery, 26 patients had experienced BCR (a PSA >0.1 ng/ml with a subsequent confirmatory measurement).
A total of 117 patients had index lesions visible on MRSI and the median number of voxels (volumetric pixel) per lesion was 3.5, which were graded as either low, intermediate, or high. Among these 117 cases, 21 (17.9%) proved to be false-positive at surgery.
Univariate analysis, adjusted for known predictive clinical variables (stage, grade, PSA), showed that the number of voxels in the index lesion, the number of high- and intermediate-grade voxels, and the percent of high-grade voxels were significantly associated with BCR risk, with hazard ratios (HRs) of 1.07, 1.07, and 1.02, respectively.
MRI risk score was not significantly associated with BCR, however.
The researchers stratified patients by numbers of index voxels and presence of high-grade voxels and found that men with 4 or more index lesion voxels at MRSI - of which at least 1 was high-grade - had significantly higher BCR rates than patients with 4 voxels including no high-grades, or 3 voxels of any grade.
Indeed, 19 of the 26 men with BCR were in this high-risk group, and 18 of the 21 men with false-positive index lesions had only 1-3 index voxels, none of which were high-grade.
"Our results suggest that we can identify a population with a high likelihood of recurrence after radical prostatectomy based on high MRSI tumor volume and grade," conclude Zakian et al.
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By Sarah Guy