• Histologically confirmed adenocarcinoma of the prostate diagnosed within the last 8 months. Patients on active surveillance with evidence of disease progression are eligible to the protocol as long as they meet the eligibility criteria and have a recent prostate biopsy (within 8 months).

• Low-risk and favourable intermediate-risk prostate cancer patients are eligible according to the following definitions:

‣ Low-risk disease defined as: Clinical stage T1-T2a and Gleason 6 and PSA ≤ 10 ng/mL

‣ Favourable intermediate-risk cancer defined by a single NCCN intermediate risk factor:

‣ \[NCCN : National Comprehensive Cancer Network\]

⁃ Clinical stage T2b

⁃ PSA \> 10 but ≤ 20 ng/mL

⁃ Gleason 7 (3+4)

‣ Lymph node evaluation by either computed tomography (CT) or magnetic resonance imaging (MRI) is optional and is left at the discretion of the treating physician.

• Age ≥ 18 years

• Eastern Cooperative Oncology Group performance status 0-1

• Patient considered medically fit for LDR brachytherapy

• Prostate volume ≤ 60 cc, measured by Trans-Rectal UltraSound (TRUS), CT or MRI, within the last 6 months.

• International Prostate Symptom Score (IPSS) ≤ 20 (alpha blockers allowed)

• No alpha reductase inhibitors use within two weeks of randomization

• No hormonal therapy is accepted

• Patients must provide a study-specified informed consent form prior to study entry.

• Patients must be willing and able to complete the EPIC-26, IPSS and SHIM questionnaires.

‣ \[EPIC-26: Expanded Prostate Cancer Index Composite score ; SHIM: Sexual Health Inventory for Men questionnaire\].