癌症血液检测离我们更近了一步

在医生探查人体内部情况的手段中，验血的侵害性最小。但说到癌症，血液就无法提供真正可靠的信息。虽然肿瘤细胞碎片确实会进入血液，但它们极为少见而且难以寻觅。因此到目前为止，医生们了解癌症状况的最佳途径是从人体内提取活体组织进行检查。

不过，基因排序方面的新进展给癌症液体活检，也就是通过血液来追踪癌症带来了更大的希望。在美国临床肿瘤学会年会上，癌症诊断公司Guardant Health的研究人员发布了令人鼓舞的研究成果。他们在1.5万名病人身上试用了该公司覆盖70种不同癌症基因的检测方法。这项技术从血液中提取微小的肿瘤DNA片段，然后对该片段进行排序，以识别肿瘤的突变类型。这有助于医生判断哪种治疗方法对病患的癌症最为有效，原因是许多抗肿瘤新药都以癌症普遍存在的突变过程为靶点。

这项研究发现，目前已获准使用的治疗药物以及处于临床试验阶段的实验性药物确实有可能对付逾三分之二病人的细胞突变。

这个研究团队包括来自加利福尼亚大学圣地亚哥分校的科学家，他们还比较了血液检测结果和验血后六个月内的传统取样活体检查结果。在接受测试的病人中，血液基因检测能正确反映98%的细胞突变。

上述发现是迄今为止证明此类血液检查能用于癌症诊断的最有力证据。这种液体活检优于取样活体检查，原因就在于众所周知的肿瘤异质性，也就是说，同一肿瘤某处的细胞和另一处的细胞可能存在差别，而取样检查通常只能从某一处提取细胞。同时，肿瘤还会逐渐发生变化，但受安全和经济性因素影响，反复进行取样检查并不实际。相反，血液检查有可能长期追踪癌症，并能更好地反映出肿瘤出现了什么样的变化。在肿瘤对当前治疗方法产生耐药性后，血液检查还有可能说明需要怎样调整治疗方案。

不过，就连参与此项工作的研究人员也认为，不能说液体活检将全面取代取样活体检查。要诊断癌症，活体检查就需要识别癌症类型并定位原发病灶。Guardant Health联合创始人兼首席执行官海尔米•埃尔图基则表示：“液体活检取代的可能是取样活体检查之后的所有活检程序。”

内布拉斯加大学医学中心内科学教授、美国临床肿瘤学会主席朱莉•沃斯博士指出：“可以想见这样的检测未来可以用于跟踪病人的情况，并在发现新突变时调整治疗方案，而且不需要对原发肿瘤进行取样检查。此外，在癌症发生转移的情况下，原发肿瘤取样检查可能成本较高并且较为危险。” （财富中文网）

译者：Charlie

审校：詹妮

A blood test is one of the least invasive ways for doctors to get a peek inside the body. But when it comes to cancer, blood isn’t exactly a reliable source of information. While tumors do shed fragments into the blood, they’re rare and hard to find, so until now, the best way for doctors to learn about tumors is to physically go in and extract snippets of them with a biopsy.

But new advances in genetic sequencing is leading to more hope for a liquid biopsy for cancer, a way to track cancer through the blood. In a study presented at the annual meeting of the American Society of Clinical Oncology, researchers from Guardant report encouraging results from a study involving 15,000 patients who were tested with the company’s test that looks at 70 different tumor genes. The technology picks up tiny fragments of DNA shed by tumors into the blood, and sequences the DNA to provide a picture of which mutations are present in the tumor. That helps doctors decide which treatments are most effective against that person’s cancer, since many of the newer anti-cancer drugs specifically target certain mutant processes common in cancer.

The study found that more than two thirds of the patients did indeed have mutations that could be addressed with currently approved drug treatments, or with experimental drugs being tested in clinical trials.

What’s more, the team of researchers, which also included scientists from University of California San Diego, also compared the blood-based results with those from a physical sample of the tumor obtained from a traditional biopsy within six months of the blood test. Among these patients, there was 98% agreement over the genetic results of which mutations were present.

Those findings are the strongest yet confirming the utility of such blood-based tests for cancer. Such liquid biopsies carry an advantage over physical biopsies since tumors are notoriously heterogeneous; cells from one part of the tumor may be different from cells from another, and biopsies typically only take cells from one part. Tumors also change over time, but repeated biopsies are not practical for safety as well as economic reasons. Blood-based testing, however, could track tumors over time and provide a better picture of how the cancer is changing, and how treatments might also have to change if the tumor is becoming resistant to an existing therapy.

But even the researchers involved in the study don’t forsee liquid biopsies replacing physical biopsies completely. In order to diagnose cancer, a biopsy is needed to establish what type of cancer is present and verify its primary location. But, says Helmy Eltoukhy, co-founder and CEO of Guardant, “what liquid biopsies might replace is every biopsy after that.”

Says Dr. Julie Vose, professor of internal medicine at the Nebraska Medical Center University Hospital and president of ASCO, “We could imagine this type of assay could be used in the future to surveil patients and change their treatments when new mutations are found, without having to biopsy the original tumor, and in cases of metastatic disease where it may be more costly and dangerous to do that.”