Radiotherapy Plus ADT Benefit Confirmed in High-risk Prostate Cancer

Not the Most Common Type of ADT

Nick Mulcahy

January 29, 2014

Radiotherapy should be part of the initial treatment for men with high-risk prostate cancer who are managed with long-term androgen-deprivation therapy (ADT), according to a major Scandinavian randomized trial.

In the study, at a median follow-up of 10.7 years, 118 of 439 men treated with hormone therapy alone died of prostate cancer, compared with just 45 of 436 men treated with combination therapy (P < .0001).

Most of the combination therapy, which was significantly beneficial out to 15 years, consisted of adding radiotherapy to long-term oral antiandrogen therapy.

The 10-year prostate-cancer-specific mortality rates were higher in the hormone therapy group than in the combination therapy group (18.9% vs 8.3%), as were the 15-year rates (30.7% vs 12.4%).

Thus, the men receiving only hormone therapy were more than twice as likely to die of their disease over time, reported lead author Sophie Dorothea Fosså, MD, PhD, from the Department of Oncology at Oslo University Hospital in Norway.

She spoke yesterday at a presscast held in advance of the 2014 Genitourinary Cancers Symposium in San Francisco.

These longer-term results come from the Scandinavian Prostate Cancer Group's Study VII, which started in 1996, and are based on mortality data from Danish, Norwegian, and Swedish death registries.

They update the 8-year results that were published in 2009 (Lancet. 2009;373:301-308). At that time, the researchers reported a 12% absolute reduction in prostate-cancer-specific mortality in the men who received the combination therapy.

The new results indicate an improvement in efficacy from 10 years to 15 years of follow-up.

"It's very interesting to see that the results improve over time," said Charles Ryan, MD, from the Helen Diller Family Comprehensive Cancer Center at the University of California, San Francisco. He moderated the press conference and was not involved with the study.

Trial Is "Somewhat Unique"

Dr. Ryan observed that the study involved lifelong use of an antiandrogen and not lifelong medical castration, which makes the trial "somewhat unique."

He was referring to the fact that other studies have used more potent long-term castration — either surgical or medical (a luteinizing hormone-releasing hormone agonist or a gonadotropin-releasing hormone antagonist) — alone or in combination with antiandrogens to interfere with the body's production of testosterone.

When the trial started in 1996, life-long medical castration was the standard of care for these men, explained Dr. Fosså.

However, adverse effects are a concern with this approach, so the researchers used less-potent life-long antiandrogens as an alternative approach.

The study participants initially received 1 injection of a testosterone-blocking hormone (short-term castration that lasts for 3 months), followed by radiotherapy for 2 months and lifelong pill-based antiandrogen therapy.

Antiandrogens for life are still the standard practice in Scandinavia. In other parts of Europe and in the United States, the standard is radiotherapy plus ADT (medical castration variety) for 2 or 3 years, Dr. Fosså noted.

All of the study participants were 75 years or younger, in good overall health, and had high-risk prostate cancer that was either locally advanced or histologically aggressive. Most cases (80%) were locally advanced, with tumor growth beyond the capsule.

In 1996, this type of extracapsular prostate cancer was considered inoperable, but that is no longer the case, Dr. Fosså explained. "Today, many urologists would operate on these patients," she said. It is not known if such surgery improves survival, compared with radiotherapy plus ADT, because there have been no randomized trials to date.

However, Dr. Fosså did state that the 10-year prostate-cancer-specific mortality of 8% seen with the combination in this trial is "comparable" to results seen after prostatectomy in such patients in other studies.

2014 Genitourinary Cancers Symposium (GUCS): Abstract 4. To be presented January 30, 2014.

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