以下内容原文发布于AACR官方博客《Cancer Research Catalyst》, 中文内容仅做参考，请点击文末“阅读原文”，阅览原文内容。
在肿瘤较小且较易治疗的早期阶段发现癌症是挽救患者生命的关键。借助乳房
X
光检查和结肠镜检查等常规筛查，可以检查出健康人是否患有癌症，这些方法大大提高了在癌症进展至致死阶段前发现它的能力。但不幸的是，仅有这些筛查手段还远远不够。
许多致命的癌症种类仍然没有任何可行的筛查方法，这意味着在发现它们时往往为时已晚。
而要及时开展可行的癌症筛查并不容易。以一名45岁的女性为例，要实现这一目的，她可能需要在一年内接受乳房X光检查、结肠镜检查、子宫颈涂片检查和皮肤检查等诸多检查，并且这还只是在她的患癌风险处于一般水平的情况下。根据她的家族病史和生活方式，医生可能会建议她接受额外的筛查项目以检测更多的癌症类型。
每项癌症筛查都需要预约不同的专家，也需要花费时间预约、前往和完成检查。除了时间上的巨大投入，这些检查项目还可能导致焦虑加重和身体不适。
那么，有没有更简单的方法呢？目前，常规血液检测已经能实现帮助医生发现糖尿病、心脏病、器官功能障碍和其他疾病的指征。
血液检测是否也能查出癌症？
许多研究人员认为，答案是肯定的。
这种方法被称为“液体活检”，与传统的肿瘤活检（需要通过手术从疑似癌症患者身上提取组织）不同，液体活检的优势在于它是非侵入性的（仅需采集患者的血液样本）。有朝一日，它甚至可以成为常规血液检查的一部分，从而让没有癌症迹象的患者也能接受检查，此外甚至可以同时检测多种类型的癌症（现有的筛查方法只能检测单一器官的癌症）。
研究人员还在探索使用血液以外的其它体液来检测癌症，例如从母乳或尿液中寻找癌症迹象。
了解更多内容，请阅读以下原文。
What Is Liquid Biopsy?
Detecting cancer early—when it is small and easier to treat—is key to saving lives. Routine screening tests like mammograms and colonoscopies check for cancer in healthy people and have drastically improved our ability to catch cancer before it turns deadly. But the unfortunate truth is that these screening tests aren’t enough.
Many of the deadliest cancers still don’t have any screening tests available, which means they often aren’t found until it’s too late.
And staying up to date with the cancer screenings that are available isn’t easy. A 45-year-old woman, for example, might need to have a mammogram, colonoscopy, Pap smear, and skin check all in the same year—and that’s just if she has an average cancer risk. Depending on her family history and lifestyle, doctors might advise even more screenings for additional cancer types.
Each of these cancer screenings requires its own appointment with a different specialist, taking time to schedule, travel to, and complete. On top of the immense time commitment, these tests might also lead to heightened anxiety and physical discomfort.
But what if there were an easier way? Routine blood tests already help doctors find signs of diabetes, heart disease, organ dysfunction, and other medical conditions.
Could a blood test detect cancer too?
The answer, according to many researchers, is a resounding yes.
Known as “liquid biopsy,” this strategy differs from traditional tumor biopsies that rely on surgically extracting tissue from a patient who is suspected of having cancer. The advantages of liquid biopsy are that it is noninvasive (all you need from the patient is a blood sample), it could someday be performed as part of routine bloodwork even for patients with no signs of cancer, and it could even look for multiple types of cancers at once (unlike existing screening tests that look for cancer in a single organ).
Researchers are also exploring using other bodily fluids to test for cancer—looking for signs of cancer in breast milk or urine , for example.
How Does Liquid Biopsy Detect Cancer?
Like all cells in the body, cancer cells release molecules into the patient’s bloodstream. If researchers can identify molecules released specifically by cancer cells, they can develop a test that looks for these molecules in blood samples to find cancer earlier and more easily than is currently possible.
Are Liquid Biopsy Tests FDA-approved for Early Cancer Detection?
A longstanding blood test to detect signs of prostate cancer has been approved by the U.S. Food and Drug Administration (FDA) since 1986, but this test (which looks for elevated levels of a protein called PSA) can be unreliable and its utility has been debated by experts.
In the intervening years, researchers have continued to develop and evaluate different liquid biopsies for cancer screening, and on July 29, 2024, the FDA approved Shield, a blood test that screens for colorectal cancer in people at least 45 years of age who have an average risk for the disease. The approval was based on clinical trial results that showed the test accurately detected 87.5% of nonmetastatic colorectal cancers and almost 90% of metastatic colorectal cancers.
Researchers are also working on newer tests that can detect multiple types of cancer from a single blood draw in people with no apparent signs of cancer. While some MCED liquid biopsies are commercially available, none are currently approved by the FDA. Additional research is needed to improve their ability to detect cancers at early stages and to understand how impactful these tests would be at saving lives. Some experts worry that these tests could, in some cases, detect slow-growing tumors that would have been harmless if left alone, leading to unnecessary treatments that come with side effects, financial costs, and stress. The benefits and risks of MCED liquid biopsies, therefore, need to be carefully weighed.
How Else Can These Tests Be Used?
Beyond early cancer detection, liquid biopsy can also be used to guide treatment in patients already diagnosed with cancer. Some liquid biopsy tests are FDA-approved to assess a patient’s eligibility for certain cancer treatments or to monitor how their cancer responds to treatment. These tests analyze molecules released by cancer cells into blood as a way to determine the tumor’s molecular characteristics and to assess tumor size before, during, and after treatment. This information can help oncologists decide the next steps in disease management.
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