Concomitant MRI-detected and MRI-undetected Prostate Cancer with Implications for Biopsy Strategies and Focal Therapy Planning: An Analysis of the PROMIS and PICTURE Trials

BACKGROUND AND OBJECTIVE: European Association of Urology guidelines now recommend performing magnetic resonance imaging (MRI)-targeted with peri-lesional biopsies rather than traditional systematic biopsies. In patients with MRI-detected prostate cancer, the characteristics and therapeutic implications of concomitant MRI-undetected disease requiring systematic biopsy to identify are unclear. This was investigated through exploratory analyses of the PROMIS and PICTURE trials. METHODS: Patients with one or two suspicious quadrants on MRI, either ipsilateral or contralateral, and who underwent 5-mm transperineal template mapping biopsy were included. MRI-detected and -undetected lesions were compared and the impact of systematic biopsies on focal therapy planning was assessed. Cancer definitions used were Grade Group 2-5 and Grade Group 3-5. KEY FINDINGS AND LIMITATIONS: Overall, 306 patients were included. A total of 240/306 (78%) had cancer diagnosed; 215/306 (70%) had MRI-detected cancer, with 44/306 (14%) having both MRI-detected cancer and additional MRI-undetected cancer. MRI-detected cancers had greater Grade Group and maximum cancer core length than MRI-undetected cancers (p < 0.001 for each). Of 127 patients eligible for focal therapy based on MRI-targeted biopsy alone, if whole gland biopsy were performed instead then 116/127 (91%) would not require a change to treatment template (p = 0.1). Adding contralateral hemigland biopsy to MRI-targeted biopsy identified all patients requiring a change to their treatment template. To ensure correct focal therapy planning for all, the number-needed-to-biopsy using additional contralateral hemigland biopsy instead of MRI-targeted biopsy alone was 12. CONCLUSIONS AND CLINICAL IMPLICATIONS: In this exploratory analysis, MRI-targeted biopsy alone was sufficient for detecting Grade Group 2-5 and Grade Group 3-5 cancer and was also sufficient for planning focal therapy, with the addition of contralateral systematic biopsies only altering focal therapy planning in 9%. Prospective validation of these findings, particularly regarding focal therapy planning, is needed.