Internet advertising systems know a lot about us. If you
want to know how much, head to Google’s web page on ad personalization (https://adssettings.google.com/u/0/authenticated).
On a recent visit I found out that Google knows of my upcoming travel plans to
Italy and Texas, a few of my hobbies, and several academic topics that I’m
learning more about. Unsurprisingly, it wasn’t correct on everything (I’m not
into extreme sports), but it knew a lot more than I would have imagined before
I visited their web page.
Over the past few years our and other research groups have shown that interactions with search
engines can be used to screen people for a variety of serious medical
conditions, both mental and physical. These include depression, eating
disorders, Parkinson’s disease, several types of solid tumor cancer, and
diabetes. However, informing people about these inferences is challenging both
technically and ethically.
This week we published a paper (https://dl.acm.org/doi/10.1145/3373720)
showing how to leverage the information that Internet advertisers have about us,
to screen for 3 types of cancer. Our results suggest that it’s indeed possible
to screen people for their likelihood of suffering from cancer before they are
diagnosed by a doctor.
Here’s how it works: when an advertiser uses Bing or Google
to advertise, they select keywords such that when a user searches for these
keywords their ads are shown. A
more sophisticated form
of advertising happens when, in addition, advertisers tell Google or Bing whenever a user who saw the ads buys the product they
were trying to sell. When advertisers do this, the advertising systems learn to
predict who, among all people use the keywords, are likely to buy a product (technically
this is known as conversion optimization). This learning is based on the
information that advertising systems have about users, including their
interests, locations and demographics.
What we did was to leverage this capability and use the
advertising system to screen people for cancer. We achieved this by showing an ad to people who searched
for information on self-diagnosis of lung, breast or colon cancers. The ad suggested help in understanding the
severity of the symptoms that people were experiencing. People who chose to click
the ads were directed to a website where, after explaining the experimental
nature of the system and asking for their consent, they were given a clinical
questionnaire about their demographics and symptoms. People who answered the questions were
given one of two indications: either that they should urgently seek medical
attention, because their symptoms were deemed serious, or that it was likely
that their symptoms weren’t indicative of cancer but medical advice should be
sought, though not urgently.
When the questionnaire indicated that a person was likely
suffering from cancer, we informed the advertising system that the person “bought”
our “product”. Within 3 weeks, the advertising systems learned to focus on
those people who probably have cancer, such that approximately 1 in 10 people who
completed the questionnaires were likely suffering from it, up from the
baseline rate of under 1%. This rate was similar for all three types of cancer.
The use of ads offers a method for interacting with people
who might be suffering from as-of-yet
undiagnosed cancer. By providing ads with an offer of help and
empowering people to select whether or not they wished to receive this help, we
overcome many of the ethical challenges associated with unsolicited diagnosis.
Our use of the sophisticated capabilities and knowledge about users that
advertising systems have, allows us to identify people with serious disease,
without having to have access to sensitive individual-level search data.
Interestingly the people who use the system most came from
countries with high Internet use and lower life span. The latter is a known proxy for the
quality of the health system.
Many health organizations use internet advertising for awareness
campaigns and for campaigns designed to encourage healthier behaviors. Our results lead us to
suggest that health systems should leverage the information that advertising
systems collect about people in order to improve population level screening
Jeffrey Hammerbacher (at the time at Facebook) once commented
that “The best minds of my generation are thinking about how to make people
click ads. That sucks.” Let’s make use of the products of those great minds to
improve outcomes for people with serious disease.