A simple blood draw can check for cancer. But who should get one?

I hadn’t planned on being this nervous. I’m a neurosurgeon. I open skulls for a living.

Over the past 50 years, I’ve had my blood drawn dozens of times and never really thought much of it. “Routine, likely to come back normal,” is what I’ve always thought. Like most people, I’ve had results that were a little off: cholesterol too high one year and blood sugar that was a bit elevated in the past, as well. Dietary changes always did the trick for me.

This time felt different, however. As I watched the phlebotomist label two tubes of blood, I thought, “this will either be nothing, or it will change everything about how I spend the next year of my life.”

The blood test is called Galleri, made by a company called Grail , and it belongs to a new class of blood tests known as multicancer early detection tests. Some people refer to them as liquid biopsies. The idea is absurdly elegant: When tumors grow, most of them shed fragments of their DNA into the bloodstream. A single blood draw can find those DNA fragments and possibly flag the earliest whispers of more than 50 cancers.

That is the point my friend Katrina Firlik made when she called me a few months ago.

Katrina is also a neurosurgeon. We are around the same age and have spent our careers living in the world of scans and certainty. She took the test on a whim, she said. She was perfectly healthy and had no symptoms whatsoever. So she was stunned when it came back positive.

A subsequent PET scan lit up with what she described as a bright lump, “like a light bulb,” sitting in her chest. It was Hodgkin lymphoma, caught so early that her own thoracic surgeon told her, only half-joking, that she might be the luckiest unlucky person he’d ever met: Unlucky because, of course, she had cancer. Lucky because he said he rarely sees tumors that small.

Katrina told me she kept coming back to a single thought: If she hadn’t taken that test, when would this thing have finally made itself known? Would it have been a persistent cough at age 50? Shortness of breath on a hike at 60? Instead, she was able to go through treatment before the disease ever got the chance to make her sick. “I didn’t have to survive a cancer crisis. I got to skip it entirely,” she told me.

I have to admit, it was a pretty compelling story. I asked her if she thought I should get the test, too. “Do you like finding cancer early?” she responded. “Who doesn’t, right?” It’s why I rolled up my sleeve and found myself having that existential moment in a blood testing lab.

The numbers around early detection are genuinely staggering. Between 1975 and 2020, routine screening and prevention efforts are estimated to have prevented about 4.75 million cancer deaths in the United States. That’s one of the great public health achievements of the last half-century.

The catch is that virtually all that benefit comes from just five screenings: breast, cervical, colorectal, lung and prostate. Every other cancer – brain, pancreatic, ovarian, most blood cancers, dozens of others – has no recommended screening test at all. These are typically found the old-fashioned way, when someone starts to feel a little off or develops unrelenting pain. That means later in the process, when they’re harder to treat and the odds have already shifted against the patient.

So, yes, I like the idea of catching cancer early. But as I started to dig into this, I realized it wasn’t quite so simple. Liking an idea and trusting a test are two different things, and the more reporting we did on this issue over the past few months, the more that gap started to bother me.

Here’s the problem, in plain terms: These tests are good at telling you the truth when they’re positive, when they have found something. If Galleri flags something, the odds that it’s a real cancer are legitimately high. It’s called the positive predictive value. Katrina is an example of that.

But a test is really only as useful as its ability to also tell you the truth when it says no. What does “negative” really mean?

That’s where things get complicated.

I reached out to Dr. Vershalee Shukla, who runs a cancer screening program for firefighters in Arizona, a population that, because of chronic exposure to toxins and carcinogens on the job, develops cancer at an elevated rate. Shukla has run close to 10,000 of these liquid biopsies over the past five years. The number of cases they’ve caught this way: fewer than a dozen.

“It’s just not picking up cancers,” she told me. One week, her team drew blood from 500 firefighters on the same day. Every single result came back negative. Sounds good, but here’s the problem with that: No one wanted to go in for their regular screenings afterward, because their negative Galleri result gave them a false sense of security.

It took Shukla and her team close to two years to convince those same firefighters to go back and get the screenings they’d been skipping. When they finally did, they found 15 with cancers.

Here’s how I now think about it: A negative result doesn’t mean you’re totally clean. It means this particular test, on this day, didn’t find anything. If you let that become an excuse to forgo your colonoscopy or mammogram or any other recommended screening test, you just traded away a good screening tool for a false sense of peace.

The company agrees, Grail told me in an email: “All of our physician and patient materials are explicit that Galleri is not a replacement for routine screening and that it should be used in addition to routine screening tests.”

Even a positive test can carry unexpected consequences because, as hard as this might be to believe, not every cancer found early needs to be treated early – or treated at all. Some tumors are so slow-growing, they will never cause a problem in your lifetime. Find one of those, and you haven’t saved a life. You’ve started what doctors call a cascade of care. That might mean more scans, more biopsies, more waiting rooms, more sleepless nights wondering if your body has somehow betrayed you.

As remarkable as these new technologies are, there is an anticlimactic truth underneath it all. We simply don’t know the answer to the most fundamental question: Do they save lives? So far, the massive, lengthy trials to be able to prove that have not been done . This kind of finding can take decades to show.

Despite all that, I took the test anyway. I won’t pretend that it was totally rational or that the weeks of waiting for the results weren’t a little brutal. I thought about my wife and kids, how I would talk them through all this if the results came back positive. Several of my physician colleagues asked why I bothered to torture myself like this. I thought about getting the same call Katrina did and being lucky-unlucky, too.

My test came back negative.

By now you know that wasn’t nothing, but it wasn’t everything, either. It didn’t clear me. It didn’t mean I get to skip my scheduled screenings this year, and I’m not going to. I have my own colonoscopy scheduled right around my birthday.

What this process gave me was a very expensive ( about $1,000) education in how to evaluate risk at a time when there are always new tests and options to assess it. Perhaps unsurprisingly, it also provided me with a renewed appreciation for the unglamorous tests we’ve trusted for decades, the colonoscopies and mammograms that nobody particularly enjoys but which come with something Galleri can’t yet offer: proof that they save lives.

What to know about multicancer early detection tests

There are two multicancer early detection tests in the direct-to-consumer market in the US: Galleri by Grail and Cancerguard by Exact Sciences.

Both tests say they can detect more than 50 cancers using a simple blood test.

They are not routinely covered by insurance and cost $700 to $1,000 out of pocket.

On September 23, advisers to the US Food and Drug Administration will meet to consider whether to recommend approval of the Galleri tests, which could encourage insurance coverage.

CNN’s Nadia Kounang contributed to this report.

我没想到自己会这么紧张。我是一名神经外科医生，我的工作就是打开颅骨。

过去五十年里，我抽血检查过几十次，从来没太在意过。“例行检查，结果应该正常。”我一直这么想。和大多数人一样，我的检查结果也偶尔会有些偏差：有一年胆固醇偏高，以前血糖也略微偏高。不过，调整饮食习惯总能帮我解决问题。

但这一次感觉却不同。当我看着抽血员给两管血液贴上标签时，我想：“这要么没什么大不了的，要么会彻底改变我接下来一年的生活。”

这项名为Galleri的血液检测由Grail公司生产，属于一种新型血液检测——多癌种早期检测。有些人也称之为液体活检。其原理极其巧妙：肿瘤生长时，大部分会将DNA片段释放到血液中。一次抽血即可检测到这些DNA片段，并有可能发现50多种癌症的早期迹象。

几个月前，我的朋友卡特里娜·菲尔利克给我打电话时也表达了同样的观点。

卡特里娜也是一名神经外科医生。我们年龄相仿，职业生涯都奉献给了各种扫描和确定性的世界。她说，她做这个检查纯粹是心血来潮。她身体非常健康，没有任何症状。所以，当结果呈阳性时，她感到非常震惊。

随后的PET扫描显示，她的胸腔里有一个明亮的肿块，就像“灯泡”一样。经诊断为霍奇金淋巴瘤，发现得非常早，以至于她的胸外科医生半开玩笑地告诉她，她可能是他见过的最幸运的不幸之人：不幸是因为她得了癌症；幸运是因为他很少见到这么小的肿瘤。

卡特里娜告诉我，她脑海里一直萦绕着一个念头：如果她没有做那项检查，这病什么时候才会发作？会不会是50岁时持续咳嗽？60岁时徒步旅行时气喘吁吁？幸好，她在疾病有机会折磨她之前就接受了治疗。“我不用经历癌症危机，我完全避开了它，”她告诉我。

我得承认，这故事挺有说服力的。我问她我是否也应该去做检查。“你想早期发现癌症吗？”她反问道，“谁不想呢，对吧？” 这就是为什么我卷起袖子，走进验血室，开始思考人生意义的原因。

早期发现带来的成果着实令人震惊。据估计，1975年至2020年间，常规筛查和预防措施使美国避免了约475万例癌症死亡。这是过去半个世纪以来公共卫生领域最伟大的成就之一。

关键在于，几乎所有这些益处都来自五种筛查：乳腺癌、宫颈癌、结直肠癌、肺癌和前列腺癌。其他所有癌症——脑癌、胰腺癌、卵巢癌、大多数血液癌症以及其他数十种癌症——都没有推荐的筛查方法。这些癌症通常是通过传统的方式发现的，比如当患者开始感觉身体不适或出现持续性疼痛时。这意味着发现时往往已是疾病晚期，治疗难度更大，患者的生存几率也已大大降低。

是的，我喜欢早期发现癌症的想法。但当我开始深入研究这个问题时，我意识到事情并没有那么简单。喜欢一个想法和信任一项检测是两回事，过去几个月我们对这个问题的报道越多，这种差距就越让我感到不安。

简单来说，问题在于：这些检测在结果呈阳性时，也就是发现问题时，能够准确地告诉你真相。如果 Galleri 检测出异常，那么它确实是癌症的概率确实很高。这叫做阳性预测值。卡特里娜飓风就是一个例子。

但一项检测的真正价值在于，当结果为“否”时，它也能告诉你真相。“阴性”究竟意味着什么？

事情就变得复杂了。

我联系了维莎莉·舒克拉博士，她在亚利桑那州负责一项针对消防员的癌症筛查项目。由于长期在工作中接触毒素和致癌物，消防员群体患癌率较高。过去五年里，舒克拉博士进行了近万例液体活检，但通过这种方法发现的病例却不到十几例。

“它根本检测不出癌症，”她告诉我。有一次，她的团队在同一天给500名消防员抽了血。所有结果都是阴性。听起来不错，但问题在于：之后没有人愿意去做常规筛查，因为Galleri检测结果为阴性让他们产生了一种虚假的安全感。

舒克拉和她的团队花了将近两年时间才说服那些消防员回去接受他们之前一直错过的筛查。最终，他们发现其中15人患有癌症。

我现在是这样想的：阴性结果并不意味着你完全健康。它只是意味着在当天进行的这项特定检查没有发现任何问题。如果你因此而放弃结肠镜检查、乳房X光检查或其他任何推荐的筛查，那你只是用一种虚假的安心感换取了一次有效的筛查机会。

Grail 在一封电子邮件中告诉我，该公司也同意这一观点：“我们所有的医生和患者资料都明确指出，Galleri 不能替代常规筛查，而应该与常规筛查测试结合使用。”

即使检测结果呈阳性，也可能带来意想不到的后果，因为，尽管这听起来难以置信，但并非所有早期发现的癌症都需要早期治疗——甚至有些癌症根本无需治疗。有些肿瘤生长极其缓慢，终其一生都不会造成任何问题。即便发现了这类肿瘤，你也并非挽救了一条生命。你只是开启了医生所说的“级联式治疗”。这可能意味着更多的扫描、更多的活检、更多的候诊室等待，以及更多辗转难眠的夜晚，你会怀疑自己的身体是否背叛了你。

尽管这些新技术令人瞩目，但其背后却隐藏着一个令人失望的事实。我们根本无法回答一个最根本的问题：它们能拯救生命吗？迄今为止，尚未进行大规模、漫长的试验来证明这一点。这类发现可能需要数十年才能得出。

尽管如此，我还是做了检测。我不会假装这完全理性，也不会否认等待结果的几周时间有多么煎熬。我想到了我的妻子和孩子，如果结果呈阳性，我该如何向他们解释这一切。我的几位医生同事问我，为什么要这样折磨自己。我想到了自己接到卡特里娜打来的那个电话，那种感觉既幸运又不幸。

我的检测结果呈阴性。

现在你应该明白，那并非无关紧要，但也并非全部。它并没有让我彻底康复。这并不意味着我可以免除今年的定期筛查，而且我也不会这么做。我的结肠镜检查就安排在我生日前后。

这个过程让我花费了大约1000美元，接受了一次非常昂贵的风险评估教育，尤其是在如今风险评估方法层出不穷的时代。或许并不令人意外，它也让我重新认识到那些我们信赖了几十年的、看似不起眼的检查的重要性，比如结肠镜检查和乳房X光检查。虽然没人喜欢这些检查，但它们却能提供Galleri目前无法提供的东西：它们能够挽救生命。

关于多癌种早期检测，你需要了解哪些内容？

美国直接面向消费者的市场上有两种多癌种早期检测测试：Grail 公司的 Galleri 和 Exact Sciences 公司的 Cancerguard。

两项检测均声称，通过简单的血液检测即可检测出 50 多种癌症。

这些治疗通常不在保险范围内，需要自费 700 至 1000 美元。

9月23日，美国食品药品监督管理局的顾问将开会讨论是否建议批准Galleri的检测方法，这可能会促进保险覆盖范围。

CNN记者纳迪亚·库南对本报道亦有贡献。