Introduction: Focal therapy has emerged as a possible treatment option in well-selected patients with localized prostate cancer. However, currently, there is a paucity of data on the long-term oncologic outcomes of focal therapy and on the risk of undertreating patients by using biopsy results and prostate magnetic resonance imaging (MRI) with PI-RADS 3-5 lesions to define focal therapy treatment templates. This study compared focal therapy templates with final pathology results after radical prostatectomy.
Methods: We retrospectively reviewed our institutional database and identified all patients with a biopsy-confirmed MRI lesion with grade group (GG)2 or GG3, and systematic biopsies or other targeted biopsies with Results: Sixty-eight patients met inclusion criteria. The mean tumor size was 1.24 cc on MRI compared to 1.79 cc on final pathology. Using the 1-cm ablation margin, in field failure was present in 31% of patients, with 76% on the craniocaudal axis; out of field failure in 45%; and any failure in 56%. Using the hockey stick template, any failure was present in 26% of patients. Among patients with posterior-predominant lesions, 63% of cases were associated with any failure using the 1-cm margin compared to 26% using the hockey stick template. In anterior-predominant lesions, 48% of cases had any failure using the 1-cm margin compared to 21% using the hockey stick template.
Conclusions: In prostate cancer patients with isolated GG2 or GG3 disease following MRI fusion biopsy, MRI underestimates tumor diameter. 1cm margins have relatively high rates of in-field and out-of-field failure. These data can be used in the planning of prospective focal therapy interventions.