Scientists create experimental breath test to detect lung cancer

  • The earlier lung cancer is detected, the more treatable it is.
  • Lung cancer detection is currently carried out using CT scans in people who are at high risk; however, this method is expensive, requires equipment, and comes with some risk.
  • Recently a group of researchers discovered that patients with lung cancer have a group of 7 volatile organic compounds (VOCs) in their breath, which could help with its detection without CT.

Lung cancer is the third most common cancer in the United States, according to the Centers for Disease Control and Prevention, but has the highest death rate.

This high death rate is partly due to the fact that lung cancer is often detected late, which means that treatment options are minimal.

A recent study carried out by researchers at the University of Louisville has demonstrated that a newly developed lung cancer detection test could determine which VOCs are the most likely to be detected in people with lung cancer.

The study was published in the journal PLOS One.

How is cancer currently detected?

Currently, lung cancer can be detected using CT scans and is offered in the U.S. to those at high risk.

There is much ongoing research into early cancer detection. From the GRAIL trial, which reported some of the results from its attempt to develop a blood test that can detect cancer and where in the body it is from, to epigenetic tests, which can reveal from cervical smear samples if a person has ovarian, breast or cervical cancer.

Recently, it was demonstrated that monitoring a biomarker in women with BRCA mutations could detect if they had ovarian cancer earlier enough to improve overall survival and money. Researchers hope that with earlier detection, lives and money can be saved as more treatment options will be available.

Detecting lung cancer

The possibility of detecting lung cancer by measuring the VOCs is another area that has received some attention.

Dr. Mike Davies of the University of Liverpool, who researches lung cancer and works closely with the lung cancer charity Roy Castle Lung Cancer Foundation told Medical News Today in an interview that the volatile chemicals detected in the breath are not necessarily from the lung cancer tumor, as chemicals are brought to the lungs by the blood from all over the body.

“Chemicals released by any part of the body, including diseases or tumors anywhere in the body, actually flow around the blood system,” he said.

“And when they reach the lungs […] they will come out in the breath. A practical example of this is ketones so the breath you get with some of diabetics, that’s the same kind of process in that it’s released in the blood system, and comes out in the breath,” he further explained.

The challenges of a breath test for cancer

Prof. Robert Rintoul, professor of thoracic oncology at Cambridge University, U.K. told MNT of the challenges of detecting and treating lung cancer.

“[T]he vast majority [of lung cancer patients], unfortunately, die of their disease. And the reason for that is all these people presenting with lung cancer, around about three-quarters of them [or 75%] present with advanced stage disease.”

This has an impact on the treatment options that are available to them.

“So although [lung cancer patients] can be offered help and treatment, that treatment is often not to cure it, and only a quarter of patients who are presenting with lung cancer probably get offered treatment that might cure. [T]herefore, in order to improve the long-term outcomes from lung cancer, we need to identify lung cancer at an early stage.”
— Prof. Robert Rintoul

One of the challenges with using VOCs to detect lung cancer is that there are many similar compounds emitted by different conditions.

Dr. Davies explained the VOCs emitted by chronic obstructive pulmonary disease (COPD), which is common in smokers who are also much more likely to have lung cancer, are similar to the VOCs emitted by lung cancer itself.

What the current study tested

In the current study, researchers developed a method to capture the exhaled breath of 414 individuals. Of these individuals, 156 had untreated lung cancer, 65 patients had benign nodules in the lung, and 193 healthy control subjects were recruited from the families of the lung cancer patients.

Most of the lung cancer patients were current or former smokers. Of the controls used, 113 were current or former smokers, and 80 were never smokers. The healthy control group were significantly younger than the group with lung cancer.

Using exhaled air sampled using a newly developed system to detect the different types of VOC present, the researchers used machine learning to determine if the VOCs detected in cancer patients were linked to their cancer.

This helped to identify a group of 7 VOCs that, when they occurred together, indicated the presence of lung cancer, authors argued in a paper published in PLOS One.

Testing biomarkers for cancer

The paper did not test the findings in a validation set, which would determine whether or not the algorithm developed to analyze the VOCs detected in exhaled breath could be used to detect lung cancer in a cohort.

Prof. Rintoul, who was not involved in the study, said that challenges exist when trying to find biomarkers for lung cancer, as you need to find a way to include people who are asymptomatic for lung cancer, so you can design a test to detect lung cancer as it has presented in them.

“The critical thing when you’re doing this type of work is to make sure you’re looking at the right population,” he said.

This means that studies need to be designed to pick up people who are symptom-free, which might not be the case if the research model is based on data and biomarkers from people who have symptomatic lung cancer.

“But then we’ve got to say, well, that’s all very well with people coming in the front door with lung cancer. But actually, it’s a different population of people who are out there in the community as well with no symptoms at all,” he added.

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