“Drug holiday” will change the standard of care, reduce side effects for men with recurring prostate cancer

05 September 2012

Toronto -

Results of a clinical trial published today in The New England Journal of Medicine shows that men with prostate cancer who are treated with intermittent courses (known as a drug holiday) of androgen-suppressing therapy will live as long as those receiving continuous therapy.

The trial was led by the NCIC Clinical Trials Group, which is funded by the Canadian Cancer Society. It found that not only do the men live as long, they may also experience greater quality of life with fewer uncomfortable side effects from continuous exposure to androgen-suppressing therapy. Side effects include hot flashes, sexual impotence, growth of breast tissue, insomnia, weight gain, worsening of diabetes, loss of muscle mass and osteoporosis. These side effects are due to the lack of testosterone produced by the drugs. Patients receiving intermittent courses of the androgen-suppressing drug reported reduced hot flashes, urinary problems and fatigue, and an increase in sexual desire.

The findings also have significant economic implications: patients on the intermittent therapy used only one-third the amount of the drug, which is very costly.

“We have known since the mid-1990’s that androgen-suppressive therapy could be used in an interrupted fashion, but we didn’t know until now that men were not sacrificing length of life in the hopes of having a better quality of life,” says Dr Juanita Crook, principal investigator and radiation oncologist with the BC Cancer Agency. “The results of this trial will change the standard of care.” Dr Crook co-led the study with Dr Laurence Klotz, a clinical urologist at Toronto’s Sunnybrook Health Sciences Centre.

Since the growth of prostate cancer depends on the male hormone testosterone, one of the commonly used treatments is a form of hormone therapy to lower testosterone (androgen) levels. Men who took part in this clinical trial had initially undergone radiation treatment for their prostate cancer, in some cases preceded by surgery, but subsequently experienced elevated PSA levels (prostate-specific antigen) indicating that their cancer had returned. A total of 1386 men participated in the trial which recruited patients from 1999 until 2005. Most were from Canada; others were from the US and the UK.

The standard treatment until now has been to use continuous therapy but this is expected to change as a result of these findings. “The findings of this research study will change the way men suffering a recurrence of prostate cancer are treated, and improve their overall quality of life, says Dr Christine Williams, VP of Research, Canadian Cancer Society.

Patients in the trial were randomized into 2 different groups: the control group of men received slow-release injections of an LHRH blocker (luteinizing-hormone-releasing hormone). Injections of the drug were given every 3 months and lasted for 3 months to provide continuous suppression of testosterone. The experimental group received the same drug but in treatment cycles that were 8 months long, interrupted for extended “drug holidays” lasting several months to years. These men were monitored every 2 months using the PSA test. If a patient’s PSA levels rose while off treatment, he would then resume treatment with the LHRH blocker for another 8-month cycle until his PSA levels dropped again, and so on.

The follow-up period of the trial was stopped early because a planned mid-trial analysis, reviewed by an independent data and safety monitoring committee, unequivocally demonstrated no difference in survival outcome between the two groups of men.

About the NCIC Clinical Trials Group
The NCIC Clinical Trials Group is a national research program of and is funded by the Canadian Cancer Society. Additional support for the trial was provided by the United States National Cancer Institute (Grant #CA077202) and Sanofi-Aventis.

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Christine Harminc

Senior Manager, Communications & Media Relations

Canadian Cancer Society

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