The index lesion and focal therapy: an analysis of the pathological characteristics of prostate cancer.

OBJECTIVE: To determine the pathological characteristics of radical prostatectomy specimens with respect to index and secondary lesions.
METHODS: A total of 100 consecutive radical prostatectomy specimens examined at a single hospital were assessed. Patients undergoing salvage prostatectomy or those who had received neoadjuvant hormonal manipulation were excluded. Preoperative data and the number, volume and Gleason grade of each tumour focus were recorded. Criteria used to define a clinically significant lesion were tumour volume ≥0.5 mL and/or Gleason pattern 4 or 5 and/or extra-capsular disease.
RESULTS: Overall, 374 foci were examined. The median number of tumours per patient was 3.5 (range 1-15). The overall median tumour volume was 1.4 mL (range 0.1-18.2), the median volume of the largest (index) tumour was 0.95 mL (range 0.1-18.2) and the median volume of the largest secondary tumour was 0.2 mL (range 0.05-1.7). There were no patients in whom the index lesion was insignificant and secondary tumours were significant (by grade or extra-capsular disease). Seventy-seven fulfilled the clinical parameters of low-to-intermediate-risk disease. If focal therapy can be delivered with the aim of ablating all clinically significant disease, with untreated areas harbouring no cancer or clinically insignificant disease, between 58.5 and 67.5% might have been suitable for such a strategy.
CONCLUSIONS: The proportion of men with low-to-intermediate-risk prostate cancer who may potentially be suitable for a focal therapy approach is unknown. The key question is whether the volume of individual lesions points to clinically significant cancer and whether ablation of these lesions alone would lead to cancer control. This research question is currently undergoing evaluation within a prospective clinical trial.