Inclusion Criteria:  Age 40 to 85 Male Prostate adenocarcinoma on biopsy Clinical stage T1c/T2a/T2b, N0, M0/Mx with no lesion larger than 2cc in volume  The following biopsy findings (biopsy must have MRI visualization and be within 6 months of planned NanoTherm® treatment):  A positive biopsy for prostate cancer from the MRI-visualized lesion, at least one of which must be Gleason 3+4 (grade group 2) Lesion must be visualized by Multiparametric Magnetic Resonance Imaging (MP-MRI) on a scan that is less than 6 months old Patient expresses a preference for active surveillance, rather than surgery or radiation, to manage prostate cancer Based on the evaluation of the study investigator, appropriate for instillation of NanoTherm® under anesthesia based on location and size of the clinical target volume (CTV)  Exclusion Criteria:  Previous treatment for cancer with radiation, androgen deprivation (including LHRH-agonists or antagonists or antiandrogens), or surgery for prostate cancer Active urinary tract infection Metallic implants below the neck Gleason 3+4 or higher cancer on prostate biopsy outside of the planned CTV Gleason 4+3 or higher on any prostate biopsy Hematological abnormality indicating increased risk of bleeding or clotting, for example low platelet count or anemia Participation concurrently in another clinical trial for prostate disease or in the last 30 days Known hypersensitivity to Axumin®