The principal objectives of the RADAR trial is to address the hypotheses; 1) that 18 months androgen deprivation in conjunction with radiotherapy is superior to 6 months androgen deprivation prior to and during radiotherapy; 2) that 18 months Bisphosphonate therapy will prevent bone loss caused by androgen deprivation therapy and further reduce relapse risk by impeding the development of bony metastases.

Traditionally androgen deprivation (by orchidectomy, or more recently by medication) has been reserved for the palliative treatment of men with advanced, incurable prostate cancer. However, evidence from large scale trials is beginning to suggest that androgen deprivation (AD) may be helpful in preventing relapse in patients with more localised disease who are treated surgically or by radiotherapy. Of the 8000 patients per annum who are treated with curative intent, one half (4000) have cancers where 'adjuvant' AD may be prescribed according to interpretation of the registered indications. There are, however, enormous variations in prescribing practices which reflect uncertainty as to the appropriate indications. An important issue is osteopenia.

The increasing use of AD in men with earlier stages of cancer, whose life expectancies exceed 3 years, has exposed many unwanted metabolic sequelae of prolonged AD, the most important being osteopenia. In 1996, with the funding support of the NHMRC and the pharmaceutical industry, TROG therefore launched a large randomised three-arm trial. Two of the arms repeated the two arms of the US Radiation Therapy Oncology Group (RTOG) 86.01 trial which, at the time, was showing early indications of benefit for the addition of two months maximal androgen deprivation (MAD), using Goserelin (Zoladex) and Flutamide, before radiation therapy and one month during. Since work from Canada had indicated that continued AD for periods longer than three months produced additional shrinkage of the prostatic tumour, the TROG 96.01 trial incorporated a third arm: six months MAD prior to and during radiotherapy. The trial completed its recruitment target of 800 eligible patients in early 2000. Although in August 2001 the median follow up time was still very short, a preliminary analysis indicated that significant increases in time to biochemical relapse had been produced by AD. In fact, the benefits of AD were independent of stage, tumour grade and initial PSA value which were confirmed also to predict time to biochemical failure. The hazard of relapse reduced to 0.75 (0.55 - 0.97, 95% confidence intervals) with 3 months AD, and still further to 0.6 (0.45 - 0.82) with six months AD.

Subsequent international developments in this area of research encouraged the design of a 'follow on' trial. A European Organisation for Research and Treatment of Cancer (EORTC) trial reported that 3 years of adjuvant ('post hoc') AD (using Goserelin alone), administered after radiotherapy, reduced relapse and improved survival in patients with locally advanced prostate cancer. The US Radiation Therapy Oncology Group (RTOG) 85.31 trial indicated that indefinite Goserelin administration after radiotherapy reduced treatment failure rates at all sites when compared with radiotherapy alone. The RTOG 92.02 trial showed that 24 months of adjuvant Goserelin also reduced failure rates in patients treated with 4 months of MAD prior to and during radiotherapy. Subset analyses of the RTOG trials, suggested that patients who gain most from prolonged AD in terms of survival are those with high grade cancers.

It was therefore logical for TROG to propose a second trial with the intention of finding out whether an additional 12 months of AD administered after radiotherapy (aka 'intermediate term' AD [ITAD]) would reduce relapse and mortality in patients treated with six months of AD prior to and during radiotherapy (aka 'short term' AD [STAD]) as in the 'best' arm of its first (96.01) trial. The availability of the potent bisphosphonate, zoledronic acid, also made it possible to find out whether or not osteopenia induced in the two arms of the proposed second trial would be prevented by a second random assignment to 18 months' bisphosphonate therapy (BP).

This is a randomised phase III multicentre clinical trial.

After informed consent is given and eligibility is checked patients will be randomised to one of four trial arms:

1. 6 months of androgen blockade with an LH-RH analogue (5 months before start of radiotherapy) (STAD),
2. 18 months of androgen blockade with an LH-RH analogue (starting 5 months before start of radiotherapy) (ITAD),
3. 18 months of therapy with zoledronic acid 4 mg by intravenous infusion every 3 months for 18 months beginning concurrently with STAD
4. 18 months of therapy with zoledronic acid beginning concurrently with ITAD.

Stratification will be according to the following criteria:

T2 / T3, 4 Gleason score 2 - 6 / 7+ Presenting PSA <10 / 10 - 20 / >20 Treatment centre

Radiation Treatment will be delivered using a conventional technique, unless the treatment centre of the participating clinician demonstrates an ability to deliver the treatment using a CRT, IMRT, or HDRB technique verified by the trial TACT.

Drug Treatment:

LH-RH analogue (LH-RHa) (Leuprorelin acetate 22.5 mg) will be delivered as a depot injection every 3 months. This will be administered as an Intramuscular injection (IMI).

Zoledronic acid 4 mg will be delivered as an intravenous infusion over 15 minutes once every 3 months for 18 months, in patients randomised to this therapy. No placebo therapy will be given to patients randomised to 'no bisphosphonate therapy' treatment arm.

Inclusion Criteria:

• Histological confirmation of adenocarcinoma of the prostate in the three months prior to randomisation
• Gleason primary and secondary pattern reported. If the volume of tumour in biopsies is too small for the pathologist to allocate a secondary pattern, the primary pattern alone is sufficient.
• Primary tumour stage T2b - 4 (UICC 2002), or T2a providing biopsies demonstrate Gleason score 7 or more, and presenting PSA 10 or more
• PSA value obtained within one month of randomisation
• No evidence of lymphatic or haematogenous metastases, as determined by negative chest x-ray, CT scan of abdomen and pelvis, and bone scan in the 3 months prior to randomisation
• ECOG performance status 0 - 1
• No concurrent medical conditions likely to significantly reduce prospects of 5 year survival
• Patient accessible to follow up at intervals specified in protocol
• Written informed consent given (signed by both patient and investigator prior to randomisation)

Exclusion Criteria:

• Previous or concurrent malignancy within previous 5 years except for non-melanomatous skin cancer
• Prostatectomy
• Prior pelvic radiotherapy
• Prior hormone treatment for prostate cancer
• Inability to complete self administered QOL questionnaire
• Prior bisphosphonate therapy
• Serum creatinine > 2 x ULN
• Osteoporosis resulting in >30% loss in vertebral height in one or more thoraco-lumbar vertebrae
• Liver disease resulting in ALT or AST levels >3 x ULN
• Prolonged continuous glucocorticoid therapy > 10 mg/day of prednisone equivalent (>6 months)
• Current treatment with bisphosphonate
• Inability to attend for follow-up at the Investigator's clinic