A study looking at how women manage symptoms that might be ovarian cancer (CLOCS)

Cancer type:

Ovarian cancer





This study looked at the products women buy to help manage symptoms that could be a sign of ovarian cancer. These symptoms might include pain in the tummy that won’t go away or bloating.

This study was open for people to join between 2019 and 2022. The team published the results in 2023.

More about this trial

Ovarian cancer is often diagnosed late when the cancer has already spread. This is because the symptoms of ovarian cancer are vague. Particularly when it’s in its early stages. 

Women often choose to take over the counter medications to manage their symptoms. Many seek advice from pharmacists, family, and the internet, rather than see their GP.

In this study, researchers looked at over the counter medications women bought before they were diagnosed with ovarian cancer. 

The women who took part all had a store loyalty card at certain high street shops. Store loyalty cards record the items people buy. So the researchers could track what they bought. 

Some women in the trial had a diagnosis of ovarian cancer. And some didn’t. 

The main aim of the study was to compare the 2 groups of people. This was to see if there was a difference in the products they bought.

Summary of results

The researchers worked with two big UK high street stores. 609 women signed up to take part in the study. Of these, 273 agreed and were eligible to share their shopping data going back over six years.

Of the 273 women who joined:

  • 153 had ovarian cancer
  • 120 didn’t have ovarian cancer 

The study team looked at pain and indigestion medication that women bought. They looked to see if there was a difference in what and how much women were buying. 

They found that women diagnosed with ovarian cancer had been buying more pain or indigestion medicines. This increase started up to 8 months before being diagnosed with ovarian cancer. This was compared to women who didn’t have ovarian cancer 

The team say this suggests that long before women have recognised their symptoms as enough to go to the GP, they may be treating them at home. 

The team found that pain and indigestion medication purchases were higher in women who went on to be diagnosed with ovarian cancer. 

The team say that more research needs to be done to confirm these findings. This would mean running a study with a larger number of women diagnosed with ovarian cancer at different stages. This larger study could also include other high street stores and look at other cancer types. The team say this new study has been funded and should hopefully open in 2024. 

The team hope this further research might help develop an alert system. This is to help people to go to the GP for symptoms earlier. 

More detailed information
There is more information about this research in the reference below. 

Please note, this article is not in plain English. It has been written for healthcare professionals and researchers.

Association Between Purchase of Over-the-Counter Medications and Ovarian Cancer Diagnosis in the Cancer Loyalty Card Study (CLOCS): Observational Case-Control Study
H R Brewer and others
JMIR Public Health Surveillance, 2023. 

We have based this summary on the information in the article above. This has been reviewed by independent specialists (peer reviewed Open a glossary item) and published in a medical journal. We have not analysed the data ourselves. As far as we are aware, the link we list above is active and the article is free and available to view.

Recruitment start:

Recruitment end:

How to join a clinical trial

Please note: In order to join a trial you will need to discuss it with your doctor, unless otherwise specified.

Please note - unless we state otherwise in the summary, you need to talk to your doctor about joining a trial.

Chief Investigator

Dr James Flanagan

Supported by

Cancer Research UK
Imperial College London
Ovarian Cancer Action

If you have questions about the trial please contact our cancer information nurses

Freephone 0808 800 4040

Last review date

CRUK internal database number:


Please note - unless we state otherwise in the summary, you need to talk to your doctor about joining a trial.

Last reviewed:

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