Treating High-Risk or Recurrent Prostate Cancer: Systemic Therapy with Local Treatment
Almost any cancer can spread at some point during its development. High-risk prostate cancer spreads early, which often results in recurrence (return of disease after treatment). To improve outcomes, high-risk prostate cancer requires systemic treatment to combat cells that might have spread prior to diagnosis and therapy. Because of this, there’s a major focus on improving the systemic therapies that can be combined with local treatment—surgery or radiation—to eliminate cells that might have spread. Systemic treatments are given through the bloodstream so they can go throughout the body, reaching any place that might harbor cancer.
One of the most common and effective forms of systemic therapy for prostate cancer is hormone therapy. While hormone therapy by itself is not curative, medications such as leuprolide (Lupron) and goserelin (Zoladex) as well as antiandrogens (flutamide or bicalutamide) keep testosterone, the main growth factor for prostate cancer, from getting to its receptor and activating cancer growth.
For many years doctors were concerned that prostate cancer could become resistant to hormone therapy, so the lethal form of prostate cancer was called “hormone refractory” or “androgen independent.” However, investigators at Seattle Cancer Care Alliance (SCCA) have shown that cancers that become resistant to lowering testosterone in the blood are actually making their own testosterone. For this reason, we believe that the majority of prostate cancers are not, in fact, hormone refractory.
Hormone therapy is commonly given with radiation therapy to men with high-risk cancer because large studies have demonstrated clinical benefits from this combination. The benefits appear to relate both to hormone therapy making prostate cancer more susceptible to radiation treatment and hormone therapy killing or suppressing cancer cells that might have already escaped from the prostate gland. Investigators at SCCA have completed studies using the hormone therapy abiraterone (Zytiga) with radiation therapy to optimize the ability of the radiation to kill the cancer, as well as to suppress any cancer outside of the prostate. Other studies are assessing the ability of degarelix (Firmagon), another form of hormone therapy, to improve efficacy of radiation therapy.
The chemotherapy drug docetaxel (Taxotere) provides benefits for men with advanced cancer, but it has not been adequately tested to see if it will benefit men with high-risk cancer localized to the prostate.
Investigators at SCCA have been instrumental in performing laboratory and clinical studies to improve systemic treatments for prostate cancer. Most of their work has focused on early use of chemotherapy to try to prevent resistance to hormone therapy by targeting cancer cells that may be resistant to hormone therapy from the outset. Treatments such as chemotherapy should be more effective at eliminating these “hormone-independent” cells that might have spread outside the prostate. Investigators from SCCA are conducting a study to determine whether early chemotherapy after radical prostatectomy for prostate cancer can kill any cells that might have spread before surgery. This study is in follow-up to determine whether chemotherapy increases the likelihood of a cure.