Amyloid and Tau PET Guide Selection and Monitoring of Alzheimer’s Therapy

Alzheimer’s disease is the most common form of dementia and can be difficult to distinguish from other causes of cognitive decline. According to the World Health Organization (WHO), 57 million people were living with dementia worldwide in 2021, with Alzheimer’s accounting for 60% to 70% of cases.

Accurate diagnosis is increasingly important because newer anti-amyloid therapies are intended specifically for patients with Alzheimer’s disease and require monitoring of treatment response. Supporting both needs, researchers have highlighted the role of brain PET imaging in selecting patients for these therapies and tracking disease-related changes during treatment.

At LMU Munich and the LMU Medical Centre (Munich, Germany), nuclear medicine teams are using amyloid and tau positron emission tomography (PET) to support Alzheimer’s diagnosis and treatment planning. Amyloid PET visualizes amyloid deposits in the brain, helping determine whether dementia is caused by Alzheimer’s disease rather than another condition. Blood and cerebrospinal fluid biomarkers can also support diagnosis, but amyloid PET may provide additional confirmation before treatment begins.

Amyloid-beta is a naturally occurring protein that can accumulate between brain cells, initially forming small clumps that eventually develop into larger plaques, often years before symptoms appear. PET tracers bind to these plaques, while anti-amyloid drugs target earlier protein aggregates and may slow disease progression by up to 30% when administered during the early stages, according to clinical trials. Early treatment is particularly important, as lecanemab and donanemab are intended for patients with mild cognitive impairment or mild dementia due to Alzheimer’s disease.

Amyloid PET can also be used to monitor response to anti-amyloid therapies such as lecanemab and donanemab. Follow-up scans can show when amyloid levels fall below the detection threshold and a patient becomes amyloid-negative, potentially allowing clinicians to consider ending treatment. In a phase 3 donanemab trial published in JAMA, 52% of participants receiving the drug completed treatment in less than 12 months, although treatment is generally planned for up to 18 months.

Tau PET provides complementary information about disease progression and prognosis. In Alzheimer’s disease, amyloid-beta and tau contribute to disrupted communication between nerve cells and progressive neurodegeneration. More than 500 amyloid and tau PET scans are performed each year at the LMU clinic for Alzheimer’s diagnosis.

The tracer used at LMU Medical Centre also generates a binding curve that helps identify amyloid-beta-associated tau deposits and assess the extent of neuronal damage, enabling more accurate predictions of disease progression and treatment response.

Clinical trials of donanemab have also shown that patients with lower tau levels may respond better to treatment than those with higher levels in the brain. According to the researchers, tau PET could therefore help identify patients most likely to benefit from available therapies and those who may experience limited benefits.

These applications are among the developments being discussed at the 39th Annual Congress of the European Association of Nuclear Medicine (EANM '26), taking place October 17–21 in Vienna, Austria, where experts are examining early experiences with PET imaging in routine clinical practice and the latest advances in nuclear medicine.

“Molecular imaging enables us to visualize functions and target structures using targeted tracers. This is vital for delivering precision medicine and tailoring treatment to the individual patient. Enormous progress is being made, particularly in the characterization and therapeutic monitoring of neurodegenerative diseases, above all in Alzheimer's disease,” said Matthias Brendel, deputy director of the Department of Nuclear Medicine at LMU Munich.

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