Radiotherapy in the treatment of prostate cancer: Accuracy and effectiveness have improved
Prostate cancer has to be confirmed histologically, usually with transrectal ultrasound biopsy of 12 different areas of the gland. The tumour is given a Gleason score to reflect aggressiveness. T-stage is determined by the extent of the primary tumour (see Box 1); differentiating between T1-2 disease (contained within the prostate capsule) and T3-4 disease (capsular breach) has important therapeutic implications, as does the presence of pelvic lymph node involvement.
Pelvic MRI best differentiates these features and is required before radical treatment, but must be undertaken before, or no sooner than four weeks after, biopsy to prevent false upstaging. A bone scan is required in high-risk patients or when there is suspicion of bone metastases.
The urology multidisciplinary team uses staging information and the PSA level to stratify the risk of each patient and determine appropriate treatment methods (see Box 2). The likelihood of cancer progression causing significant health problems is weighed against the patient's life expectancy from comorbidities and the expected side-effects of treatment.
There are no randomised controlled trials comparing radical prostatectomy with radiotherapy for localised disease, and observational series are subject to considerable patient selection bias. External beam radiotherapy (EBRT) or brachytherapy and prostatectomy appear equivalent in terms of overall survival for low- and intermediate-risk patients. Active surveillance is appropriate and without prejudice to longevity in some patients.1 Treatment decisions are therefore based on the patient's preferences with regard to logistics and side-effects.
For some patients, such as those with obstructive symptoms, surgery may be more appropriate, while non-surgical options are preferred in the frail or elderly. High-risk patients usually undergo EBRT with androgen deprivation therapy (ADT) if treated radically. Ten-year biochemical relapse-free survival is about 80% for all groups treated radically.2 Whether patients with involved lymph nodes should receive a radical treatment or primary ADT is debated, but EBRT with intensity-modulated radiation therapy (IMRT) is the main radical option.
Radical external beam therapy
The principle of this form of radiotherapy is that a linear accelerator generates megavoltage X-ray beams to deliver a tumoricidal dose of ionising radiation to the target volume, comprising the entire prostate and usually the seminal vesicles. Treatment of the iliac lymph nodes produces a disease-free survival advantage in high-risk node-negative patients only (with no overall survival advantage).3
The decision to target these nodes varies in practice, because irradiating them substantially increases the volume treated, increasing toxicity. EBRT has evolved considerably as technology has improved. Conventional radiotherapy was planned using bony landmarks on two-dimensional X-rays to approximate the position of the prostate. There was little shielding of normal tissue and the volume treated was large owing to the uncertainty about the position of the target organ.