Abstract
Objectives:The rationale for directing targeted biopsy towards the centre of lesions has been questioned in light of prostate cancer grade heterogeneity. In this study, we assess the assumption that the maximum cancer Gleason grade (Gleason grade hotspot) lies within the maximum dimension (volume hotspot) of a prostate cancer lesion.Methods:3-D histopathological models were reconstructed using the outputs of the 5-mm transperineal mapping (TPM) biopsies used as the reference test in the pilot phase of Prostate Mri Imaging Study (PROMIS), a paired validating cohort study investigating the performance of multi-parametric magnetic resonance imaging (MRI) against transrectal ultrasound (TRUS) biopsies. The prostate was fully sampled with 5 mm intervals; each core was separately labelled, inked and orientated in space to register 3-D cancer lesions location. The data from the histopathology results were used to create a 3-D interpolated reconstruction of each lesion and identify the spatial coordinates of the largest dimension (volume hot spot) and highest Gleason grade (Gleason grade hotspot) and assess their concordance.Results:Ninety-four men, with median age 62 years (interquartile range, IQR= 58–68) and median PSA 6.5 ng ml−1 (4.6–8.8), had a median of 80 (I69–89) cores each with a median of 4.5 positive cores (0–12). In the primary analysis, the prevalence of homogeneous lesions was 148 (76% 95% confidence interval (CI) ±6.0%). In all, 184 (94±3.2%) lesions showed concordant hotspots and 11/47 (23±12.1%) of heterogeneous lesions showed discordant hotspots. The median 3-D distance between discordant hotspots was 12.8 mm (9.9–15.5). These figures remained stable on secondary analyses using alternative reconstructive assumptions. Limitations include a certain degree of error within reconstructed models.Conclusions:Guiding one biopsy needle to the maximum cancer diameter would lead to correct Gleason grade attribution in 94% of all lesions and 79% of heterogeneous ones if a true hit was obtained. Further correlation of histological lesions, their MRI appearance and the detectability of these hotspots on MRI will be undertaken once PROMIS results are released.
Highlights
Correct risk attribution is of key importance to guide appropriate management for men with prostate cancer
Our current diagnostic pathway based on transrectal ultrasound (TRUS) guided biopsy can result in inaccurate risk stratification in up to half of all men diagnosed.[1]
MpMRI results are blinded to clinicians performing the biopsies and to pathologists reporting the biopsy results
Summary
Correct risk attribution is of key importance to guide appropriate management for men with prostate cancer. Our current diagnostic pathway based on transrectal ultrasound (TRUS) guided biopsy can result in inaccurate risk stratification in up to half of all men diagnosed.[1] This can result in missed diagnoses and undertreatment as well as the more commonly recognised issues of over-diagnosis and over-treatment.[2,3,4,5,6]. Recent research has focused on using multi-parametric magnetic resonance imaging (mpMRI) to improve the diagnostic accuracy by introducing tumour location at the time of biopsy.[7,8,9] The provision of information on tumour location means that biopsies can be directed to the region of interest rather than be solely spread across the prostate as currently done with random TRUS biopsies. Some have argued that the ‘targeted approach’ might result in employing fewer needle deployments than we have previously used.[10,11] If this is to happen—and it would be desirable if it could— we would need to know where within the ‘target’ to direct those needles
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