Standardization of reporting discontinuous tumor involvement in prostatic needle biopsy: a systematic review

Discontinuous tumor involvement (DTI) is a not uncommon finding in the tumor in prostate needle core biopsies undertaken for diagnosis of prostate cancer (PCa). The objective of this review is to establish a clear definition of DTI in order to provide a standardized method of measurement which reliably reflects pathologic features and disease progression following radical prostatectomy (RP). A systematic literature search was performed using PubMed up to March 2020 to identify studies of PCa patients which included needle biopsies containing DTI and matched subsequent RP treatment with or without follow-up information. The methodology and quality of reporting of DTI are reviewed, compared, and summarized. DTI is a frequent finding in diagnostic biopsy for PCa (up to 30%). Six studies were compared by methods of measurement used for predicting pathologic features and outcomes which are observed in subsequent RP. In most cases with DTI (> 90%), intervening benign tissue in the tumor core was less than 5 mm. DTI found in the biopsy was likely to be associated with a single, irregular tumor nodule going in and out of the plane of the section, but DTI was not associated with multiple small foci of the tumor. Immunohistochemistry (IHC) also demonstrated that about 75% of cases of DTI shared an IHC profile which supports the concept that DTI most likely comes from a homogeneous tumor nodule. Furthermore, DTI was associated with positive surgical margin (PSM) and bilateral tumor in RP specimens. Compared to additive measurement (with the subtraction of intervening benign tissue), linear measurement (including intervening benign tissue) of DTI was more accurately predictive of aggressive disease in the RP including higher pT stage, PSM, and greater actual extent of the tumor. However, the advantage of linear measurement was lost in cases where there was an upgrade from the biopsy to the RP which may result from undersampling. For cases with either very small tumor foci or very extensive cancer volume, no difference was observed in these two methods of measurement. DTI in core biopsies may represent undersampling of a larger irregular nodule but likely does not result from multifocality and is similarly unlikely to represent multiclonality. Linear measurement of DTI was more accurately predictive of post-RP pathologic findings and oncologic prognosis. This method should be applied for patient selection for AS.