Introduction
Ovarian Cancer is the eighth most common cancer in women worldwide, and about one in
five women with ovarian cancer do not receive treatment, because they are too unwell by the
time they are diagnosed. Symptoms of ovarian cancer are non-specific or can be associated
with other common conditions, and women experiencing these symptoms have been shown
to self-manage them using over-the-counter medication. Results from a recent proof of
concept study suggest there may be an increase in the purchases of pain killers and
indigestion medication 10-12 months before ovarian cancer diagnosis. We propose a casecontrol study, as part of a larger project called the Cancer Loyalty Card Study (CLOCS), to
investigate whether a significant change in medication purchases could be an indication for
early signs of ovarian cancer, using data already collected through store loyalty cards.
Methods and Analysis
Using a retrospective case-control design, we aim to recruit 500 women diagnosed with
ovarian cancer (cases) and 500 women without ovarian cancer (controls) in the United
Kingdom who hold a loyalty card with at least one participating high street retailer. We will
use pre-existing loyalty card data to compare past purchase patterns of cases with those of
controls. In order to assess ovarian cancer risk in participants and their purchase patterns, we
will collect information from participants on ovarian cancer risk factors and clinical data
including symptoms experienced before diagnosis from recruited women with ovarian
cancer.
Ethics and dissemination
CLOCS was reviewed and approved by the North West - Greater Manchester South Research
Ethics Committee (19/NW/0427). Study outcomes will be disseminated through academic
publications, the study website, social media, and a report to the research sites that support
the study once results are published.
Study Registration Numbers
CLOCS is registered with ISRCTN (14897082), NIHR portfolio (CPMS 43323), and
clinicaltrials.gov (NCT03994653).