A 68-year-old man with no prior PSA screening presents with lower urinary tract symptoms and is found to have a PSA of 8.5 ng/mL and a suspicious nodule on digital rectal examination. A transrectal ultrasound-guided biopsy confirms adenocarcinoma of the prostate (Gleason score 7, 3+4). MRI pelvis shows no extraprostatic extension. What is the most appropriate next step in management?