Cancer Loyalty Card Study 2 (CLOCS-2)

Cancer is one of the leading causes of mortality worldwide and is responsible for an estimated 9.6 million deaths yearly. Cancer-related deaths can be reduced if patients are diagnosed and treated early. Delay in cancer diagnosis can occur at any point along the diagnostic spectrum, from the first observation of symptoms to the start of treatment. Diagnosing cancer when it is still at an early stage, before it has spread, gives surgery, radiotherapy and other treatments the best chance of working. Therefore, early diagnosis is the most important way to improve cancer outcomes.Most of the cancers usually presents with vague and non-alarming symptoms. Most individuals are diagnosed late when the cancer has already spread, and the prognosis is poor. There are over 200 different types of cancer that can cause many different signs and symptoms. Sometimes symptoms affect specific body areas, such as abdomen or skin. But signs can also be more general, and include weight loss, tiredness (fatigue) or unexplained pain. The type of symptoms varies from person to person. The major reasons for not presenting to the GP with symptoms such as these are "not wanting to waste the GP's time" and normalisation of these symptoms. The persistence of a symptom, social influence and awareness encourage help-seeking behaviours in primary care. However, few believe their symptom(s) might be a sign of cancer. Consequently, people might choose to self-manage their symptoms by using over-the-counter medication, and to seek advice from other sources, (pharmacists, family, internet), rather than a primary care physician. RATIONALE FOR CURRENT STUDY An early cancer diagnosis is essential for receiving treatment as early as possible to have the best chance for successful treatment. Early diagnosis of cancer can be challenging. Sometimes, the cancer symptoms resemble common illnesses and could resolve with the use of over-the-counter medications and other remedies until they become persistent or debilitating. The present study focuses on ten cancer forms: colon, oesophageal, stomach, liver, bladder, uterine, vulval, ovarian, endometrial and pancreatic. Patients diagnosed with the cancers mentioned above often report experiencing vague symptoms (such as abdominal or back pain, indigestion, feeling full etc). They often use over-the-counter medication to manage their symptoms before seeing a doctor. Information about how often and what products participants purchase (e.g. pain killers, digestive products and natural remedies) to care for these symptoms could help identify these cancers a few crucial weeks or months earlier and encourage people to seek help sooner from their doctors.

Sex

All

Minimum age

18 Years

Inclusion Criteria (ALL):

* Individuals aged \>18 years of age
* Individuals must be residing in the United Kingdom at the time of giving informed consent
* Individuals must be registered with an NHS GP Practice
* Individuals must meet the criteria of ONE of the groups. For example, to be eligible for Group 1 (Cases), individuals must have been diagnosed with one of the following cancer types in the last 24 months: Bladder, colorectal (bowel), endometrial, liver, oesophageal, ovarian, pancreatic, stomach (gastric), uterine, or vulval; whereas for Group 2 (Controls), individuals must not have received a cancer diagnosis of any type in the last 6 years (except where the diagnosis was of non-melanoma skin cancer).
* Individuals must be a primary registered cardholder\* of one of the loyalty cards listed below, and consent to share their loyalty card data with the study team
* Tesco Clubcard
* Boots Advantage Card
* Provision of written informed consent
* Willing and able to comply with all required study activities

  * The primary registered card holder, i.e., the person who is named on the loyalty card account, must also enrol into the study, if someone other than the registered primary card holder from the same household, wants to take part in the study.

Exclusion Criteria (ALL):

* Individuals under the age of 18 years
* Non-UK residents, at the time of giving informed consent
* Individuals without an eligible loyalty card, or who have no one in their household who has an eligible loyalty card
* Individuals who are not the primary registered cardholder in their household and where the primary registered loyalty card holder is not willing to join the study, and/or where the primary registered cardholder does not make purchases for or on behalf of the individual

Exclusion Criteria (CASES):

• Individuals will not be able to join as a case if:

* they have been diagnosed with an eligible cancer type more than 24 months ago (except where the diagnosis was non-melanoma skin cancer).
* they have received an ineligible cancer diagnosis within the last 6 years except where the diagnosis was non-melanoma skin cancer).

Exclusion Criteria (Controls):

• Individuals will not be able to join as a control (Group 2) if:

o they have received any cancer diagnosis in the last six years (except where the diagnosis was non-melanoma skin cancer).

• DERIVEDToopchiani S, Codling S, Pondeca Y, Kaur S, Horeau K, Brewer H, Cross A, Delaney B, Faisal AA, Peters C, Goulding J, Hirst Y, Sundar S, Flanagan JM. Cancer loyalty card study-2 (CLOCS-2): protocol for an observational case-control study focusing on the patient interval in cancer diagnosis. BMJ Open. 2026 May 13;16(5):e117937. doi: 10.1136/bmjopen-2026-117937. PMID 42128509