AbstractBackgroundPartial gland ablation (PGA) is a new option for treatment of prostate cancer (PCa). Cryotherapy, an early method of PGA, has had favorable evaluations, but few studies have employed a strict protocol using biopsy endpoints in men with clinically significant prostate cancer (csPCa).Methods143 men with unilateral csPCa were enrolled in a prospective, observational trial of outpatient PGA‐cryotherapy. Treatment was a 2‐cycle freeze of the affected prostate part. Participants were evaluated with MRI‐guided biopsy (MRGB) at baseline and at 6 months and 18 months after treatment. Absence of csPCa upon MRGB was the primary endpoint; quality‐of‐life at baseline and at 6 months after treatment was assessed by EPIC‐CP questionnaires in the domains of urinary and sexual function.ResultsOf the 143 participants, 136 (95%) completed MRGB at 6 months after treatment. In 103/136 (76%), the biopsy revealed no csPCa. Of the 103, 71 subsequently had an 18‐month comprehensive biopsy; of the 71 with 18‐month biopsies, 46 (65%) were found to have no csPCa. MRI lesions became undetectable in 96/130 (74%); declines in median serum PSA levels (6.9 to 2.5 ng/mL), PSA density (0.15 to 0.07), and prostate volume (42 to 34cc) were observed (allp< 0.01). Neither lesion disappearance on MRI nor PSA decline correlated with biopsy outcome. Urinary function was affected only slightly and sexual function moderately.ConclusionIn the near to intermediate term, partial gland ablation with cryotherapy was found to be a safe and moderately effective treatment of intermediate‐risk prostate cancer. Eradication of cancer was better determined by MRI‐guided biopsy than by MRI or PSA.