Weight loss jabs such as Mounjaro and Wegovy could make some cancer scans less effective, leading to unnecessary tests and possible delays in treatment, experts suggest.

The drugs, collectively known as GLP-1s, have helped millions lose up to a fifth of their body weight but may alter how tissue appears on PET-CT scans used to diagnose and stage cancers.

The changes could cause healthy tissue to be misinterpreted as potentially cancerous, meaning some patients may face extra investigations and anxiety while awaiting results.

British researchers at Alliance Medical, a leading provider of diagnostic imaging in the UK, identified the issue after noticing unusual patterns in patient scans.

PET-CT scans combine CT and PET imaging, using a mildly radioactive liquid called a tracer to highlight areas where cells are more active than normal. Brighter spots can indicate cancer, though they may also reflect infections or inflammation.

“We noticed unusual uptake in one of our patients on a GLP-1 agonist, which prompted a wider review across our network,” said Dr Peter Strouhal, medical director at Alliance Medical and lead author of the study.

“We found that these altered patterns are increasingly common, yet there is currently no national or international guidance in the UK addressing this emerging issue.”

The review of several PET-CT scans found atypical tracer patterns among GLP-1 users that “could be misinterpreted” as hot spots or potentially cancerous areas.

“Recognising the characteristic uptake associated with GLP-1 agonists helps avoid unnecessary anxiety and interventions, ensuring patients receive the right care, at the right time, without detours or doubt,” Dr Strouhal said.

Researchers said larger studies involving more data are needed before recommendations can be made to change PET-CT scan guidelines for weight loss jab users.

They advised clinicians to consider a patient’s medical history when interpreting results.

It follows earlier US research suggesting GLP-1 drugs could interfere with breast-cancer chemotherapy medicines.

That study tracked hundreds of women with early-stage triple-negative breast cancer during and after treatment.

Twenty-five were already taking GLP-1s alongside other diabetes drugs and continued doing so while undergoing chemotherapy.

Two years later, 28 per cent of the women on GLP-1s had fully responded to treatment and were clear of cancer, compared with 63 per cent of those not using the drugs.

Researchers also found GLP-1s had entered tumour and immune cells in tissue samples from the patients.

“Use of GLP-1 use may need to be carefully considered during breast cancer therapy,” said Dr Bethania Santos, oncologist and researcher at UT Southwestern Medical Center in Dallas, who presented the study at the San Antonio Breast Cancer Symposium.

However, experts at the time said the drugs themselves may not have reduced the effectiveness of chemotherapy.

People with advanced diabetes who require several medicines already have a higher risk of breast-cancer recurrence.

The study did not prove whether weight-loss drugs help or hinder the success of cancer therapy.

Scientists have developed an innovative technique to observe Alzheimer’s disease as it progresses in the brain – a breakthrough that could accelerate the development of new treatments.

The new method uses light to detect and measure the build-up of amyloid plaques – sticky protein clumps that are a key characteristic of Alzheimer’s – at different depths in the brain.

It is the first time such measurements have been made in living animals as they move naturally, rather than under anaesthetic or in fixed positions.

The research was carried out by the University of Strathclyde in partnership with the Istituto Italiano di Tecnologia, the University of Padua and the Technical University of Denmark, combining expertise in neuroscience, physics and biomedical imaging.

Professor Shuzo Sakata at Strathclyde and senior author of the study said: “Being able to monitor changes in the brain as they happen – in real time and across different brain regions – is a major step forward.

“It will help researchers understand how Alzheimer’s disease develops and test whether new treatments are working, more quickly and accurately than before.”

A special fluorescent dye that attaches to amyloid plaques in the brain was used.

Ultra-thin optical fibres were then applied to shine light into the brain and measure how much of the dye was present – providing a clear picture of how much plaque had formed.

The system was tested in mice that had been genetically modified to develop Alzheimer’s-like symptoms. The results closely matched those seen in postmortem brain tissue, confirming the accuracy of the new technique.

The research was funded by the European Union’s Horizon 2020, the Medical Research Council, part of UKRI, and Alzheimer’s Research UK.

“This approach allows us to track the disease over time in the same subject, and opens new doors for studying the progression of Alzheimer’s and how it responds to treatment,” said Dr Niall McAlinden, co-author and expert in photonics at Strathclyde.

The team is now working to improve the system’s capabilities and explore its use in studying other characteristics of Alzheimer’s disease.

NeuroClin – formerly known as Glasgow Memory Clinic – has partnered with Advance Tests to launch Scotland’s first commercially available blood biomarker test for early Alzheimer’s detection.

Designed for people with mild cognitive impairment (MCI) – subtle problems with memory and thinking – the LucentAD Complete test helps determine whether these symptoms are likely due to Alzheimer’s.

Dementia affects more than 90,000 people in Scotland and nearly one million across the UK each year.

Early diagnosis is becoming increasingly important following the recent UK approval of new disease-modifying drugs lecanemab and donanemab.

“We know that changes in the brain linked to Alzheimer’s begin years before symptoms appear,” said Dr Jennifer Lynch, medical director at NeuroClin.

“This new blood biomarker test helps us detect potential Alzheimer’s earlier, giving people access to lifestyle advice, and access to new disease-modifying treatments or research opportunities.”

The launch marks the first time a clinically validated blood test for Alzheimer’s has been available in Scotland outside a research trial setting, following national NHS trials exploring single-marker biomarker tests.

This new version uses a multi-marker approach and is now commercially available.

Developed by Lucent Diagnostics, the test is already widely used across the US, supported by multiple peer-reviewed studies and now covered by the Medicare system.

At NeuroClin, the new blood biomarker test will form part of a staged diagnostic pathway beginning with memory testing, followed by the blood test, genetic testing and specialist support where appropriate.

Dr Simon Worrell, chief medical officer at Advance Tests, said: “Bringing this diagnostic test to Scotland for the first time is a major milestone – not just for Advance Tests, but for patients and clinicians across the country.

“We are witnessing a rare and important moment in health innovation, where breakthroughs in diagnostics are aligned with breakthroughs in treatment.

“With newly approved drugs now available, and growing evidence that early lifestyle changes can delay progression, early diagnosis has never been more valuable.”

Henry Simmons, chief executive at Alzheimer’s Scotland, added: “While we wish blood biomarker tests were routinely available on the NHS, this is not yet the case.

“We welcome NeuroClin taking the lead in offering this service in Scotland, as earlier diagnosis can help people and families get answers sooner, plan ahead and access the right support and emerging treatments.”