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Four months of androgen deprivation combined with external beam radiation slowed growth of prostate cancer—especially bone metastases—by up to eight years, according to a long term study from the University of California in San Francisco and collaborating sites (Journal of Clinical Oncology 2008 Jan 2 doi: 10.1200/JCO.2007.13.9881).
The study, which began in 1987, evaluated 456 men at high risk, with a median age of 70. They had large prostate tumours (5 by 5 cm), and many had high Gleason scores (7-10) indicating that cells were higher grade and usually more aggressive, and high concentrations of prostate specific antigen (>20 ng/ml).
The men were randomly assigned to four months of androgen deprivation hormone and external beam radiation (224 men) or to external beam radiation alone (232 men). The hormone therapy was 3.6 mg goserelin every four weeks and 250 mg flutamide three times a day, beginning two months before radiation and continuing through the radiation. Follow-up for living patients was 11.9 years for men given combined treatment and 13.2 years for radiation alone.
Although few patients with such large tumours are seen in the United States because of widespread testing for prostate specific antigen, about 50000 to 70000 of the 300000 men diagnosed with prostate cancer each year in the US might be suitable for this treatment, lead author Mark Roach III of the University of California in San Francisco told the BMJ. He is a professor of radiology and a professor of urology at the university.
The combined short term androgen deprivation plus radiation had “a dramatic effect on clinically meaningful endpoints,” the investigators say, and did not increase the risk of cardiovascular events, a controversy with androgen deprivation.
Men who received combined androgen deprivation and external beam radiation were less likely to die from prostate cancer within 10 years than men who received radiation alone (23% v 36%). Fewer men receiving combined therapy had metastatic disease (35% v 47%). Disease-free survival rates at 10 years were higher in the group that received the combined treatment (11% v 3%) and these men had fewer biochemical failures (seen as a rise in concentrations of prostate specific antigen—65% v 80%).
Other studies have shown that giving radiation first followed by hormone deprivation treatment is not as effective. Neither is hormone deprivation therapy and radical prostatectomy.
Sequential treatment—hormone deprivation treatment followed by radiation—seems the most effective, Dr Roach told the BMJ.
The cardiotoxicity of androgren deprivation drugs is controversial. In this study, no statistically significant difference in cardiovascular events was seen between the men who received the combined treatment and the men who received only radiation, although the numbers of cardiovascular events were slightly higher for men who received the combined treatment. Dr Roach pointed out that patients who survived longer because of the combined treatment were more likely to be alive to develop cardiovascular events.