ASCO Updates: New Treatments on the Horizon in Prostate Cancer

The American Society of Clinical Oncology (ASCO) hosted the annual Genitourinary Cancers Symposium in San Francisco this past February, which brought together about 3,000 cancer researchers, oncologists, industry professionals, advocates and survivors to report on advances in cancers of the prostate, as well as kidney, testicular and penile. Below are the top stories in prostate cancer presented at the meeting.

Prostate cancer has seen its share of progress over the past few years, including several new drugs that have been approved for patients with metastatic disease. Two clinical studies were announced at the ASCO Genitourinary Cancers Symposium that foreshadow additional therapies that will help further extend survival and improve quality of life.

Alpharadin (radium-223) uses alpha particles, a type of ionizing radiation that penetrates only a few layers of cells and avoids injury to nearby tissue, to kill cancer cells that have spread to the bone, while MDV3100 works by preventing the tumor cells from using testosterone that can spur cancer growth.

The Alpharadin trial included 922 patients with castration-resistant prostate cancer (CRPC) with bone metastases who had previously received Taxotere (docetaxel), were Taxotere ineligible or had refused Taxotere. The patients were randomized to Alpharadin or placebo, with all patients receiving best supportive care. It prolonged survival by 25 percent (14 months versus 11.2 months) and delayed the time to a patient’s first skeletal-related event, such as spinal cord compression or bone fracture, from 8.4 months to 13.6 months. Side effects were minimal and included neutropenia and diarrhea.

The MDV3100 trial included 1,199 patients with advanced CRPC who had progressed after treatment with Taxotere and hormone therapy. The drug increased survival by 35 percent over placebo (18.4 months versus 13.6 months), lowered PSA levels and delayed cancer growth by an average of five months. Side effects included diarrhea, fatigue and hot flashes.

Nicholas Vogelzang, MD, chairman and medical director of the Developmental Therapeutics Committee of the US Oncology Network, a division of McKesson Specialty Health, called the results unprecedented during a press briefing held before the conference. “This is going to definitely change the way we take care of patients every day in the office.”

A study examining three types of radiation therapy in early-stage prostate cancer found the standard of treatment is better than a more expensive, newer form of radiation using proton beams instead of X-rays. Researchers examined data from more than 12,000 Medicare patients with early-stage prostate cancer who were treated with one of three forms of radiation: intensity-modulated radiation therapy (IMRT), conformal radiation therapy (CRT, an older form of radiation) or proton-beam therapy. Patients who received IMRT had fewer occurrences of bowel problems and hip fractures than CRT. While CRT costs the least, it was associated with a higher rate of recurrence. Patients who received proton-beam therapy, which is the most costly of the three, had a higher rate of gastrointestinal side effects but a recurrence risk similar to patients who received IMRT.

In a study comparing prostate cancer treatments, researchers compared prostatectomy, external-beam radiation therapy (EBRT) and brachytherapy, a form of radiation where radioactive wires or seeds are implanted near the prostate tumor. More than 130,000 patient records were reviewed for cost, toxicity and further treatment for side effects. After a median of more than five years, the study found that brachytherapy had the lowest cost per patient-year. EBRT was found to be the most expensive per patient-year and the most toxic, with gastrointestinal problems and bladder bleeding. Although brachytherapy came out on top, it’s the least utilized treatment of the three, with only 12 percent of the patient population studied undergoing brachytherapy.

When researchers found that men who exercised after a prostate cancer diagnosis fared better, the next step was to learn why. Past research showed that patients who exercised at least three hours a week lowered their risk of death by about half, and reduced the risk of death specifically from prostate cancer by 61 percent.

In a new study, researchers from the University of California, San Francisco and Duke University examined 70 men with earlystage, low-risk prostate cancer who were under watchful waiting instead of active treatment. Patients were grouped into two categories: those who exercised vigorously at least three hours a week and those who did not. Exercises included jogging, tennis and swimming laps.

After looking at changes in gene expression and pathways between the two groups, researchers found 184 genes were different, including those that are involved in tumor suppression.

“This was a small study with provocative findings that should be interpreted cautiously and warrant confirmation in a larger study,” says June Chan, ScD, the study’s senior author, during a press briefing held before the symposium. “These preliminary data suggest that DNA repair in the prostate gland is one mechanism through which vigorous physical activity may protect against prostate cancer progression, and there are potentially more.”

The next steps include a larger study of men on watchful waiting and an examination of the effects of exercise in men after a cancer recurrence. In the future, this information could be used to predict, monitor and prevent prostate cancer progression.