Could a breathalyzer detect cancer? - Julian Burschka

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How is it that a breathalyzer can measure the alcohol content in someone’s blood, hours after they had their last drink, based on their breath alone? And could we use this same technology to detect disease by analyzing a person’s breath, without having to use more invasive diagnostic tools like biopsies, blood draws, and radiation? Julian Burschka details the complicated process.

Lesson by Julian Burschka, directed by Cabong Studios.

How is it that a breathalyzer can measure
the alcohol content in someone’s blood,

hours after they had their last drink,
based on their breath alone?

Exhaled breath contains trace amounts
of hundreds, even thousands,

of volatile organic compounds:

small molecules lightweight enough
to travel easily as gases.

One of these is ethanol,
which we consume in alcoholic drinks.

It travels through the bloodstream
to tiny air sacs in the lungs,

passing into exhaled air
at a concentration 2,000 times lower,

on average, than in the blood.

When someone breathes
into a breathalyzer,

the ethanol in their breath
passes into a reaction chamber.

There, it’s converted to another molecule,
called acetic acid,

in a special type of reactor that produces
an electric current during the reaction.

The strength of the current
indicates the amount of ethanol

in the sample of air,
and by extension in the blood.

In addition to the volatile
organic compounds like ethanol

we consume in food and drink,

the biochemical processes of our cells
produce many others.

And when something disrupts
those processes, like a disease,

the collection of volatile
organic compounds in the breath

may change, too.

So could we detect disease
by analyzing a person’s breath,

without using more invasive
diagnostic tools

like biopsies, blood draws, and radiation?

In theory, yes,

but testing for disease is a lot more
complicated than testing for alcohol.

To identify diseases,

researchers need to look at a set
of tens of compounds in the breath.

A given disease may cause
some of these compounds

to increase or decrease in concentration,
while others may not change—

the profile is likely to be different
for every disease,

and could even vary for different stages
of the same disease.

For example, cancers are among
the most researched candidates

for diagnosis through breath analysis.

One of the biochemical changes
many tumors cause

is a large increase
in an energy-generating process

called glycolysis.

Known as the Warburg Effect,

this increase in glycolysis results
in an increase of metabolites like lactate

which in turn can affect a whole cascade
of metabolic processes

and ultimately result
in altered breath composition,

possibly including an increased
concentration of volatile compounds

such as dimethyl sulfide.

But the Warburg Effect is just one
potential indicator of cancerous activity,

and doesn’t reveal anything
about the particular type of cancer.

Many more indicators are needed
to make a diagnosis.

To find these subtle differences,

researchers compare the breath
of healthy people

with the breath of people
who suffer from a particular disease

using profiles based on hundreds
of breath samples.

This complex analysis
requires a fundamentally different,

more versatile type of sensor
from the alcohol breathalyzer.

There are a few being developed.

Some discriminate
between individual compounds

by observing how the compounds move
through a set of electric fields.

Others use an array of resistors
made of different materials

that each change their resistance
when exposed to a certain mix

of volatile organic compounds.

There are other challenges too.

These substances are present
at incredibly low concentrations—

typically just parts per billion,

much lower than ethanol concentrations
in the breath.

Compounds’ levels may be affected
by factors other than disease,

including age, gender, nutrition,
and lifestyle.

Finally, there’s the issue

of distinguishing which compounds
in the sample

were produced in the patient’s body

and which were inhaled
from the environment

shortly before the test.

Because of these challenges,
breath analysis isn’t quite ready yet.

But preliminary clinical trials
on lung, colon,

and other cancers
have had encouraging results.

One day, catching cancer early
might be as easy as breathing in and out.