Should the Primary Tumor Be Treated in Patients With Metastatic Prostate Cancer?
By Bryan Tutt
A new clinical trial aims to find which patients, if any, are most likely to benefit from such treatment.
The prostate tumor usually is not treated in patients with metastatic disease unless the tumor progresses and causes local symptoms. Instead, patients typically undergo a sequence of systemic therapies, starting with hormone therapy (also called androgen deprivation), which can be done by orchiectomy but is most often done with injections of luteinizing hormone–releasing hormone agonists or antagonists. Unfortunately, complications from local progression occur in 30%–45% of patients whose primary prostate tumors have not been previously treated with radiation or surgery.
“There are two schools of thought about local therapy in the setting of metastatic prostate cancer,” said Brian Chapin, M.D., an assistant professor in the Department of Urology. “Some believe that treating the primary tumor may have a biologic effect on the metastatic sites. These people theorize that such treatment could delay disease progression and even death.
“Other physicians believe that treating the primary tumor will have no effect on metastatic disease and should be done only in the setting of symptomatic local progression for palliative reasons,” Dr. Chapin continued. “But there has never been a study to determine whether that is true.”
Dr. Chapin is the principal investigator of a phase II trial in which patients with metastatic prostate cancer receive systemic hormone treatment for 6 months and then are randomly assigned to continue hormone treatment only or continue hormone treatment and also undergo definitive treatment of the primary tumor.
The primary tumor may be treated with surgery or radiation; the modality is chosen according to the physicians’ discretion and the patient’s preference. “Each patient is seen by a urologist, a radiation oncologist, and a medical oncologist,” Dr. Chapin said. “We get together and determine which modality is appropriate for a particular patient.”
In patients who undergo surgery, Dr. Chapin may perform an open or a robotic prostatectomy with pelvic lymph node dissection, depending on the extent of the disease. Patients who undergo radiation therapy may receive intensity-modulated radiation therapy or proton therapy.
The trial is enrolling men with metastatic, androgen-dependent prostate cancer who are candidates for surgery or radiation therapy. The trial is currently available only at MD Anderson, but Dr. Chapin said the trial will soon be opening at additional sites.
The primary endpoint of the trial is the time to disease progression, which is determined by an increase in the level of prostate-specific antigen or by clinical evidence of progression.
Several correlative studies will be performed to determine which subgroups of patients are most likely to benefit from treatment of the primary tumor. The researchers hope that biomarkers found in immunological profiling, magnetic resonance imaging, or surgical biopsies can be used to guide future treatment.
“We think treating the primary tumor will help some people a lot, some people a little, and some people not at all,” said Ana Aparicio, M.D., an assistant professor in the Department of Genitourinary Medical Oncology and a co-investigator of the trial. “It is too early to recommend definitive intervention to the primary tumor as standard therapy in patients with metastatic prostate cancer outside a clinical trial,” she said.
Dr. Chapin agreed, adding that it will likely be 2 years before preliminary results are available. However, he was optimistic. “We’re hoping we can improve outcomes for patients with metastatic prostate cancer,” he said.
Dr. Aparicio concurred. “I’m excited about the trial,” she said. “It could potentially change the landscape of how we treat the disease.”
For more information, contact Dr. Ana Aparicio at 713-563-6969 or Dr. Brian Chapin at 713-792-3250.
Other articles in OncoLog, March 2014 issue: