Dr. Urban Emmenegger. (Photograph by Doug Nicholson)
About 75 per cent of prostate cancers that require treatment will be cured by surgery or radiation. The remaining 25 per cent will recur and spread to other places in the body, a process called metastasis. At this stage, prostate cancers are typically treated with androgen deprivation therapy (ADT), also known as hormone therapy.
Androgens (male hormones, including testosterone) help prostate cancer grow. Blocking androgen production slows progression of the disease. But usually, sometime after two years or so, the cancer no longer responds to ADT alone. While Sunnybrook’s Odette Cancer Centre provides care for patients across the spectrum of the disease, medical oncologist Dr. Urban Emmenegger, specializes in much-needed research and treatments for prostate cancer at advanced stages when hormone therapy no longer works on its own.
Conventional hormone therapy impairs the production of androgens in the testicles, the major, but not only, source of male hormones. One of the newest androgen-deprivation drugs used at Sunnybrook blocks production of male hormones everywhere in the body and even inhibits the prostate cancer cells from producing their own hormones.
“When combining this drug with conventional hormone therapy, most patients will respond at first – only for the cancer to again become resistant after a while. However, in some patients, not all of the metastases become resistant,” says Dr. Emmenegger. He looks for ways to strategically tailor novel treatments for men who have a combination of both resistant and treatable metastases.
In collaboration with radiation oncologist Dr. Patrick Cheung, Dr. Emmenegger is conducting a clinical trial on the effectiveness of stereotactic body radiotherapy to stop the growth of such resistant, “rogue” metastases. The high-dose radiation finely targets up to five rogue tumours or progressing tumours, while the continued hormone therapy treats the stable tumours.
This clinical trial was inspired by one man whose prostate cancer had spread to his spine after having been on an experimental treatment for a number of years. “He was treated with radiation while continuing the study medication, and his PSA came down again,” says Dr. Emmenegger. “Now, 18 months later, his PSA is increasing again, and the cancer has further spread. But, in essence, we have gained a year and a half.”