A New Ally against Cancer


By Eric von Hofe E. フォン・ホフ
English 日本語 日本語
For decades cancer specialists have offered patients three main therapies: surgery, chemotherapy and radiation. (Some cancer survivors pointedly refer to this harsh trinity as “slash, poison and burn.”) Over the years continual refinements in these admittedly blunt instruments have made the more severe side effects increasingly manageable. At the same time, effectiveness has improved markedly. And new, very targeted drugs (Herceptin and Gleevec) have become available for a few specific cancers. All told, the average five-year survival rate for invasive cancers as a group has risen from 50 percent to 66 percent in the past 30-plus years. In spite of these gains, many cancer survivors will not have a normal life span.  この数十年間,がん患者が受ける治療は主に,手術,化学療法,放射線療法の3つだった(がんを克服した患者はしばしば,この過酷な3大治療を “切られる,毒を飲まされる,焼かれる”と辛辣に表現する)。
Researchers have long suspected that they could add a weapon that would dramatically increase cancer survival rates without producing serious side effects if they could just figure out how to prod the body’s own immune system to do a better job of fighting malignancies. But decades of effort met with one failure after another. In the 1980s, for instance, overheated hopes that an immune system molecule called interferon would rouse the body’s defenses to cure all or most cancers were dashed after a few more years of research. Today interferon has a place but is not the cure-all once envisioned. By the first decade of this century a great number of clinical trials were being conducted using lots of different types of vaccine-related approaches, but nothing seemed to be working. It was starting to look as though the long-hoped-for general weapon against a broad range of tumors would never materialize.  もし患者自身の免疫系を刺激してがんとうまく闘わせる方法がわかれば,重い副作用を起こさずに患者の生存率を劇的に高める武器になるのではないかと,研究者たちはかねて考えてきた。いわゆるがんワクチンによる治療だ。だがそうした試みは,何十年にもわたって失敗を繰り返してきた。例えば1980年代,免疫系で働くインターフェロンと呼ばれる分子を使って体の防御機能を高めれば,ほとんど,あるいはすべてのがんを治せるかもしれないとの期待が高まった。しかしその後数年の研究で,そうした夢はついえた。今日,インターフェロンは医療現場で日常的に使われているが,かつて期待されていたような万能薬ではない。
It still has not. But something happened in the summer of 2010 suggesting that the age of false starts and blind alleys in the effort to awaken the immune system may finally be drawing to a close: the U.S. Food and Drug Administration approved the first vaccine to treat a cancer. The drug, called Provenge, is not a cure, but it—along with standard chemotherapy—already has given hundreds of men with advanced prostate cancer a few extra months of life.  この夢は今も実現していないが,2010年夏,大きな変化があった。免疫系を活性化させる試みは,出だしでつまずいた上に袋小路の時代が長く続いたが,それがようやく終わりつつあるのかもしれない。米食品医薬品局(FDA)が初のがん治療用ワクチンを承認したのだ。プロベンジと呼ばれるその薬は,がんを治すわけではないが,通常の化学療法と併用することで,進行した前立腺がん患者の生存期間を数カ月延ばす。すでに数百人が治療を受けている。
This positive turn of events occurred after scientists reexamined a few fundamental assumptions about how the immune system works against cancer cells as well as how tumors fight back against immunological attacks. Today cancer researchers are cautiously optimistic that we can develop additional, very specific immune-boosting therapies that can be used routinely alongside surgery, chemotherapy and radiation to subdue cancer while triggering side effects that are no worse than a bad cold.  事態が前に進んだのは,免疫系がどのようにがん細胞に作用し,がん細胞が免疫系の攻撃にどのように対抗するかについて,基本的な考え方が見直された結果だ。今日がんの研究者らは,手術や化学療法,放射線療法と併用してがんを抑え,副作用はひどい風邪程度ですむ,きわめてがん特異的な追加的免疫療法を開発できるだろうと慎重ながら前向きな期待を抱いている。