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Blood Tests Shown Able to Identify Early Lung Cancer

lung illustration

(Kai Stachowiak, Pixabay)

4 June 2018. Results from a large-scale clinical trial show an analysis of blood samples can detect and identify the presence of characteristic DNA indicating a person may have early stages of lung cancer. Findings from the study are scheduled for presentation today by a team from Dana-Farber Cancer Institute in Boston and Grail Inc. in Menlo Park, California that developed the test at the annual meeting of American Society of Clinical Oncology, or ASCO, in Chicago.

Lung cancers, both small cell and non-small cell, are the second most common type of cancer, accounting for 14 percent of all new cancer cases. Only breast cancer in women and prostate cancer in men have higher rate of occurrence. American Cancer Society estimates some 234,000 people in the U.S. will have lung cancer in 2018, leading to more than 154,000 deaths. The group says more people die from lung cancer than other forms of the disease for men and women, eclipsing deaths for colon, breast, and prostate cancers combined.

Grail Inc.’s technology tests blood samples for the presence of DNA circulating in the blood stream characteristic of tumors to detect, but also identify the type of cancer. Circulating tumor DNA, says the company, makes up only a small fraction of the DNA in blood, resulting in weak signals from tumor DNA, thus requiring intense analysis to separate these signals from background noise. Grail says it sequences DNA captured in blood generating a terabyte of data on each patient, with a deep level of analysis that includes machine learning to determine the type and severity as well as the presence of cancer.

The company is sponsoring a clinical trial enrolling some 15,000 participants to help develop and validate its technology. Of the 15,000 individuals in the trial, known as the Circulating Cell-Free Genome Atlas, 10,500 participants are cancer patients while the remaining 4,500 are a cancer-free comparison group. So far, about 12,000 participants are enrolled at 141 sites in the U.S. and Canada. All participants are providing blood samples, while cancer patients are also offering tissue samples from their tumors, with the individuals’ medical records  tracked annually for 5 years.

A team led by lung cancer specialist Geoffrey Oxnard at Dana-Farber Cancer Institute is providing one of the first reports from the trial at the ASCO meeting. The researchers focused on a subset of 1,627 participants divided about equally between newly diagnosed cancer patients and cancer-free individuals for comparison. Blood samples from participants were analyzed with 3 methods in development by Grail:

 – Targeted sequencing of 507 genes to find non-inherited mutations

 – Whole genome sequencing, also to detect non-inherited genomic variations

 – Whole genome sequencing, where DNA is first treated with sodium bisulfite to highlight  changes in the DNA caused by methylation, where the chemical structure of DNA is altered by disease or injury.

The researchers were looking particularly at the ability of the tests to identify the 127 known lung cancer patients in the sample, which ranged from an early-stage localized form of the disease to advanced cases where the cancer metastasizes or spreads to other parts of the body. The results show the targeted sequencing correctly identified the about half (51%) of the earlier stage cancers and the vast majority (89%) of late-stage cancer cases. Whole genome sequencing accurately characterized nearly as many (41%) of the earlier stage cancers and about the same percentage (87%) of the advanced stage disease cases as the targeted sequencing, with whole genome plus bisulfite sequencing returning similar identifications, 38 percent of early stage cases and 89 percent of late stage cancers.

While the findings show high accuracy rates for detecting and identifying cancer, the sequencing processes also found more than half (54%) of non-inherited mutations were caused by a non-cancerous white blood cell condition called clonal hematopoiesis of indeterminate potential. or CHIP, associated with aging. Nonetheless, the authors say the results are encouraging enough to continue development of the tests to provide better tools for early-stage lung cancer diagnosis, but also better accounting for CHIP conditions.

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