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奪去麥凱恩生命的腦癌為何如此難以醫治?今后情況會如何?

Sy Mukherjee 2018年09月06日

2018年約有2.4萬美國人被診斷出患有此類癌癥,其中僅有三分之一左右能活過5年。

大家可能已經聽說了,此前一直和惡性腦癌作斗爭的參議員約翰·麥凱恩于8月25日去世,享年81歲。麥凱恩曾參加總統選舉,是美國政壇傳奇人物。

對于這位來自亞利桑那州的共和黨人,外界高度贊譽并全面回憶了他的政治生涯和他對公眾的貢獻。毫無疑問,這樣的舉動會越來越多。但密切關注奪去麥凱恩生命的潛伏殺手同樣重要——那是一種惡性腦癌,叫做多形性膠質母細胞瘤。

就統計數據而言,被診斷出膠質母細胞瘤無異于宣判死刑。腦癌和神經系統癌癥通常都是致命疾病。實際上,據美國國家癌癥研究所介紹,2018年約有2.4萬美國人被診斷出患有此類癌癥,其中僅有三分之一左右能活過5年。

美國癌癥學會指出,具體來說,膠質母細胞瘤占所有腦癌和神經系統癌癥的16%,有關此類病例的數字更是觸目驚心: 20-44歲之間的患者(這樣的病例較為罕見),其5年存活率為19%;在45-54歲的患者中,該數字下降到了8%;對于55-64歲的較高齡患者,5年存活率僅有5%,可謂機會渺茫。公開病情時麥凱恩已經80歲了(前副總統喬·拜登的兒子博·拜登同樣死于該疾病,去世時年僅46歲)。

這種病為什么會這么可怕?這在很大程度上和此類腫瘤的惡性程度有關,另外還因為手術、化療和放療等有副作用的治療手段存在局限性。

對此,醫生、佛羅里達大學神經外科學教授杜恩·米切爾博士上周一在新聞網站The Conversation上表示:

“膠質母細胞瘤的一個額外特點是其侵略性。它的腫瘤細胞其實會慢慢脫離主要腫塊,將自己深深地嵌入正常大腦中,而且經常隱藏在血腦屏障后面,這是人體的一種保護性屏障。” 米切爾寫道:“這種侵略性意味著雖然神經外科手術往往可以去除膠質母細胞瘤的核心腫塊,但它像手指一樣的侵略性突起物會伸展到大腦的其他區域。這些游離狀的癌細胞小塊無法通過手術有效移除。”

因此,治療其他類型癌癥的常規方法對付不了這樣聰明又惡毒的對手。同時,鑒于大腦的復雜結構及其在方方面面的關鍵作用,我們還看不到在很多癌癥中對付膠質母細胞瘤所取得的那些進展,比如用免疫療法或基因技術來治療皮膚癌、肺癌和血癌。

不過,近幾年科學家做出了一些(非常、非常初步)的樂觀判斷。美國神經外科醫生協會指出,試驗性膠質母細胞瘤測試正在對“基因療法、高精度放療、免疫療法以及和疫苗聯合進行的化療”進行檢驗。但該協會也冷靜地指出,這些處于早期階段的技術平均只能將患者壽命延長三個月。(財富中文網)

譯者:Charlie

審校:夏林

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As you’ve likely heard, Sen. John McCain, former presidential candidate and a larger-than-life figure in American politics, passed away Saturday at age 81 following a battle with an aggressive form of brain cancer.

There have been plenty of tributes to and reflections on the Arizona Republican’s political career and record of public service. Those will, no doubt, continue to proliferate. But it’s also important to home in on the insidious disease that claimed McCain’s life—an aggressive form of brain cancer called glioblastoma multiforme (GBM, or just glioblastoma, for short).

A glioblastoma diagnosis, statistically speaking, amounts to a death sentence. Brain and nervous system cancers in general are deadly. In fact, just about one in three of the approximately 24,000 Americans diagnosed with such cancers in 2018 are likely to still be alive five years later, according to the National Cancer Institute (NCI).

Glioblastoma specifically makes up 16% of all brain and nervous system cancers—and the numbers are even more dire in these cases, says the American Cancer Society. If the disease manifests between the ages of 20 and 44 (a relatively rare occurrence), there’s a 19% chance of survival five years after diagnosis; among those 45 to 54, that drops to 8%; and for older Americans aged 55 to 64, the five-year relative survival rate is a dismal 5%. McCain was in his 80s when his diagnosis was publicly revealed. (Beau Biden, son of former Vice President Joe Biden, also died of the disease, but at the age of 46.)

Just why is the prognosis so dire? A lot of it has to do with just how aggressive this specific kind of tumor is, and the limitation of buzzsaw approaches such as surgery, chemotherapy, and radiation.

Dr. Duane Mitchell, a physician and professor of neurosurgery at the University of Florida, had this to say in The Conversation on Monday:

“An additional characteristic of GBM is the invasive nature of the disease. GBM tumor cells essentially crawl away from the main tumor mass and embed themselves deep within the normal brain, often hidden behind a protective barrier known at the blood-brain barrier,” Mitchell writes. “This invasive feature means that while neurosurgeons can often remove the main central tumor mass of a GBM, the invasive finger-like projections protrude into other areas of the brain. The distant islands of tumor cells that have migrated away cannot be effectively removed by surgery.”

Thus, the normal courses of treatment for other kinds of cancers may not prove effective against such a clever and malevolent foe. At the same time, the complexities of the brain’s structure—and its critical role in, well, everything—have made it so that we have yet to see the same kind of progress against glioblastoma that we have in so many cancer, such as immunotherapies and gene-based treatments for skin, lung, and blood cancers.

But scientists have sounded some (very, very early) notes of optimism in recent years. “[G]ene therapy, highly focused radiation therapy, immunotherapy, and chemotherapies utilized in conjunction with vaccines” are being tested in experimental glioblastoma trials, the American Association of Neurological Surgeons notes—while adding the sobering note that these early-stage technologies have only boosted patients’ survival rates by a median of three months.

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