Potential new standard of care for prostate cancer

A new combination treatment for localised prostate cancer is leading researchers to suggest a new standard of care is emerging for this disease.

The treatment, which combines hormone therapy, radiotherapy and a drug for preventing bone loss, is likely to reduce the spread of the disease by more than 40% without increased long-term side effects.

Prostate cancer is the most common cancer diagnosed in Australia and the third most common cause of cancer death. It is more common in older men, with 85% of cases diagnosed in men over 65 years of age.

Localised but aggressive prostate cancers account for about 35% of new diagnoses of prostate cancer in Australia and New Zealand each year and more than 50% of all prostate cancer deaths.

The findings come out of a 5-year follow-up study of the 03.04 RADAR trial, a clinical trial coordinated by the Trans-Tasman Radiation Oncology Group that involved men who were newly diagnosed with localised but aggressive prostate cancer.

“Such a result is obviously of massive importance to newly diagnosed men with localised but aggressive prostate cancer, their partners and their families. This is because the RADAR patients were spared the many long-term side effects associated with longer durations of testosterone suppression of between 28 and 36 months now commonly used in conjunction with radiotherapy around the world,” said Professor Jim Denham, radiation oncologist at the Calvary Mater Newcastle, Conjoint Professor with the University of Newcastle and lead author of the study.

The main long-term side effect of current treatment is bone loss - bones are often affected by prostate cancer and can also be damaged by prolonged hormone treatment.

Trial participants received six months of hormone treatment (testosterone suppression with leuprorelin), followed by radiotherapy - this hormone treatment has previously been shown to improve the results of radiotherapy for men with early prostate cancer. Participants were then randomly allocated to receive no further treatment or an extra 12 months of leuprorelin and/or 18 months of a drug to prevent bone loss (zoledronic acid) given in combination with the first and second leuprorelin treatments.

For men with the most aggressive cancers - those with Gleason scores of 8-10 - the combination of 18 months of testosterone suppression and zoledronic acid plus radiotherapy emerged as the most effective treatment.

Men with less aggressive cancers - Gleason score 7 or less - benefited most from 18 months testosterone suppression plus radiotherapy without zoledronic acid.

Denham said the results were better than expected - the treatment would likely have a knock-on effect of a 30-40% lower death rate among men with this type of cancer.

The results point to emerging new standards of care for prostate cancer, especially if the findings hold true at the 10-year patient follow-up in 2017.

“The only downside is that zoledronic acid, which costs about $2500 for this course, is not subsidised for use in men with locally advanced prostate cancer,” Denham said. “However, cancer centres in Australia and New Zealand may be able to purchase the medication at lower cost in the coming months so they can make it available at discounted prices.”

The RADAR trial enrolled 1071 men with newly diagnosed aggressive but localised prostate cancer between 2003 and 2007 from 23 centres across Australia and New Zealand. It was supported by National Health and Medical Research Council grants and funding from other sources, including Novartis Pharmaceuticals and Abbvie Pharmaceuticals, University of Newcastle, Calvary Health Care, Hunter Medical Research Institute (HMRI) and the Maitland Cancer Appeal.

Prostate cancer is scored according to the Gleason grading system, which is based on the cancer’s microscopic appearance. Cancers with a higher Gleason score are more aggressive and have a worse prognosis.

The study has been published in The Lancet Oncology.