ホルモンレベルにより前立腺がんの生存率が予測できる

ベースラインのホルモンレベルが高値であると転移性虚勢抵抗性前立腺がんの生存率が良好なことが予知できるようである

High baseline hormone levels appear to predict improved survival in metastatic castration-resistant prostate cancer

アンドロゲン阻害薬abirateroneで治療された虚勢抵抗性前立腺がん患者で、ベースラインホルモンレベルが高値の患者はホルモンレベルが低い患者と比較し全生存期間が長いようであるとのデータが2012年AACR学会で発表された。この前向きサブスタディにおいて研究者らは、abirateroneとプラセボを比較した無作為化phase IIIトライアルのデータを評価し、abirateroneの承認に繋げた。ベースラインのホルモンレベルが高いと、ベースラインのホルモンレベルが低い場合と比較し、初回治療にかかわらず全生存率が有意に高かった。ホルモンレベルが高くプラセボを投与された患者は、ホルモンレベルが低くプラセボを投与された患者よりも生存率が50%高かった。さらに、ベースラインのホルモンレベルが高い患者および低い患者において、abirateroneを使用した方がプラセボよりも全生存期間が長期であった。ベースラインホルモンレベルが高くabirateroneを投与された患者の全生存期間は、ホルモンレベルが低くプラセボを投与された患者の全生存期間の2倍であった。このデータが確認されれば、ホルモン、特に副腎アンドロゲンにより転移性虚勢抵抗性前立腺がん患者の治療有効性を予測する新たな方法が医師に提供されることになる。

Patients with castration-resistant prostate cancer treated with the androgen inhibitor abiraterone and who had high baseline hormone levels had longer overall survival compared with patients with low hormone levels, according to data presented at the AACR Annual Meeting 2012, held in Chicago, March 31 - April 4.

If confirmed, these data mean that levels of hormones, specifically adrenal androgens, may provide physicians with another way to predict the efficacy of therapy in patients with metastatic, castration-resistant prostate cancer, according to Charles J. Ryan, M.D., associate professor of clinical medicine and urology at University of California-San Francisco Helen Diller Family Comprehensive Cancer Center in San Francisco, California.

"We have identified that patients who have higher levels of androgen compared with those with lower levels have a better prognosis overall and a better prognosis when receiving abiraterone than patients with lower levels of androgens," said Ryan. "Patients with low hormone levels seem to have a worse prognosis overall; however, they still benefitted significantly from receiving abiraterone as opposed to receiving placebo."

In the past, this form of prostate cancer was referred to as hormone-refractory prostate cancer. However, this term is no longer used because, in recent years, researchers have discovered that certain drugs, like abiraterone, which are essentially hormone therapies, improve outcomes and survival rates.

In this prospective substudy, Ryan and colleagues evaluated data from a randomized phase III trial that compared abiraterone to placebo and led to the approval of abiraterone. They categorized patients according to high levels or low levels of hormones.

The results indicated that higher baseline hormone levels were associated with significantly higher overall survival in patients regardless of initial treatment compared with low baseline levels. Patients assigned to placebo and who had high hormone levels had nearly 50 percent improvement in survival compared with those assigned to placebo and who had low hormone levels. In addition, abiraterone was associated with longer overall survival compared with treatment with placebo in patients with high and low levels of baseline hormones.

Patients assigned to abiraterone who had high baseline levels of hormones had almost twice the overall survival compared with those with low levels of hormones assigned to placebo.

"We used to think that it was not necessary to measure hormone levels once they were below normal — that was in part due to the fact that we were using insensitive assays," Ryan said. "However, now we know that they have prognostic and predictive significance and that physicians treating these patients should think about conducting hormone tests."

According to Ryan, more work is required to determine how these data will inform the standard-of-care management of patients with prostate cancer; however, it is likely that these data will affect the design of future clinical trials.

The study was sponsored by Cougar Biotechnology, which is owned by Johnson & Johnson.