Prostate Indeterminate Lesions on Magnetic Resonance Imaging-Biopsy Versus Surveillance: A Literature Review

Context: The indeterminate multiparametric prostate magnetic resonance image (mpMRI) lesion is one which cannot be classified as "positive" or "negative" for suspected cancer. Currently, there is no consensus on how to manage patients with indeterminate mpMRIs where areas cannot be classified as positives or negatives (Prostate Imaging Reporting and Data System [PI-RADS] 3 or Likert 3).

Objective: To define the concept of indeterminate lesion and describe the management strategies that may be adopted for these patients.

Evidence Acquisition: A literature search of the PubMed database was performed including the search terms "prostate indeterminate lesions", "PI-RADS 3", "Likert 3", "magnetic resonance imaging", and "prostate cancer".

Evidence Synthesis: There is no universally accepted definition of what constitutes an indeterminate lesion on mpMRI. This is partly due to the experience of the reporting radiologist and their willingness to call a lesion indeterminate, knowing that this may have consequences for biopsy decisions. This is also partly due to the significant variation in mpMRI acquisition parameters used between different sites. Strategies for managing the indeterminate lesion include: (1) biopsy, where there is a highly variable prevalence of prostate cancer (PCa), reflecting the differences in clinically significant PCa definitions, mpMRI protocols and interobserver variability in characterization of indeterminate lesions and (2) surveillance, where early results suggest that this strategy may be of value for some selected patients with prostate-specific antigen (PSA) monitoring and/or interval mpMRI. The use of prebiopsy MRI, in conjunction with traditional clinical parameters and secondary biomarkers-nomograms, may allow a more accurate selection of patients who can avoid biopsy.

Conclusions: A strategy of close surveillance based on PSA monitoring and interval mpMRI is a feasible management option for motivated patients with indeterminate mpMRI. This surveillance strategy could result in fewer men needing to undergo biopsy, and although early results are promising, long-term results for such a strategy are awaited.

Patient Summary: In some patients who have an MRI scan of their prostate, the scan may identify an area which may or may not contain cancer. This area is typically called the "indeterminate" lesion. In this report, we attempted to define the concept of indeterminate lesion on multiparametric magnetic resonance (mpMRI) and described the strategies that may be performed for these patients. The use of mpMRI in conjunction with traditional clinical parameters may allow more accurate risk stratification and assessment of the need for prostate biopsy.