🟠 Moderate Evidence
Anti-amyloid monoclonal antibodies have transformed Alzheimer’s disease treatment, but clinicians now face a new challenge: determining which patients should continue therapy and for how long. According to a viewpoint published in The Lancet eBioMedicine, amyloid positron emission tomography (PET) imaging may address this gap by providing quantitative baseline measurements and guiding individual treatment decisions in resource-constrained healthcare systems.
Key takeaways
- Anti-amyloid monoclonal antibodies (lecanemab and donanemab) reduce amyloid at the population level, but individual treatment response varies widely
- Amyloid PET imaging can establish baseline target engagement and support ongoing treatment decisions in clinical practice
- The shift from diagnostic imaging to treatment governance represents a fundamental change in how PET scans support Alzheimer’s care
- Healthcare systems must develop protocols for using PET data to optimise therapy—continuing, switching, or stopping treatment based on individual response
The Shifting Role of Amyloid PET in Alzheimer’s Disease Care
From diagnostic clarification (2010–2020) to treatment governance and target engagement monitoring (2024 onwards)
Source: The Lancet eBioMedicine, 2026 | Georgian Medical Journal News
From Diagnostic Tool to Treatment Optimisation
For the past two decades, amyloid PET imaging served primarily as a diagnostic instrument—confirming amyloid pathology in patients with cognitive decline and helping clinicians distinguish Alzheimer’s disease from other dementia subtypes. The approval of lecanemab by the US Food and Drug Administration in 2023 and subsequent adoption of donanemab marked a decisive shift in Alzheimer’s disease management. According to the viewpoint published in The Lancet eBioMedicine, these disease-modifying therapies now require clinicians to address a more nuanced question: which patients should remain on therapy, and for how long?
Clinical trial data demonstrate that both lecanemab and donanemab reduce amyloid burden at the group level, but individual responses vary substantially. The viewpoint emphasises that this heterogeneity demands a shift in how healthcare systems deploy amyloid PET. Rather than using scans solely to confirm diagnosis, clinicians should leverage quantitative PET measurements to establish individual baseline amyloid burden before initiating anti-amyloid therapy. This baseline reference becomes crucial for assessing whether an individual patient is responding to treatment.
The Challenge of Treatment Governance in Resource-Constrained Systems
Most healthcare systems face significant constraints on drug access, imaging availability, and long-term monitoring capacity. The viewpoint highlights a critical gap: clinical trials do not provide clear guidance on duration of therapy, optimal stopping criteria, or the role of re-treatment after discontinuation. In practice, this means clinicians must make these decisions with limited evidence and competing pressures.
Amyloid PET can address this uncertainty by providing quantitative data on whether an individual patient’s amyloid burden has declined meaningfully during therapy. According to the viewpoint, PET-guided treatment decisions could help healthcare systems allocate expensive anti-amyloid monoclonal antibodies more efficiently—continuing therapy in patients showing clear amyloid reduction, switching to alternative approaches in non-responders, or discontinuing treatment in patients who have achieved substantial amyloid clearance. This represents a shift from population-level efficacy data to individual patient-level treatment governance. See our coverage of clinical updates for more on emerging Alzheimer’s therapies.
Amyloid PET imaging, combined with anti-amyloid monoclonal antibodies, enables healthcare systems to shift from diagnostic imaging alone to quantitative baseline assessment and ongoing treatment governance—supporting individualised decisions on therapy continuation, switching, or discontinuation.
— Authors of viewpoint, The Lancet eBioMedicine (2026)
Operationalising PET-Guided Treatment Protocols
Implementing PET-based treatment governance requires healthcare systems to develop new clinical protocols. The viewpoint suggests that baseline PET scans should be obtained before initiating anti-amyloid therapy to establish a quantitative reference. Follow-up scans at defined intervals (e.g., 6–12 months) would then reveal whether the individual patient’s amyloid burden has declined, plateaued, or progressed despite therapy.
This approach aligns with established principles in oncology, where baseline and follow-up imaging guide treatment decisions for individual patients. However, Alzheimer’s disease care has historically relied on cognitive assessments (Mini-Cog, Montreal Cognitive Assessment) rather than imaging to monitor response. The viewpoint argues that amyloid PET offers a more direct measure of target engagement—documenting whether the drug is achieving its intended biological effect in that specific patient.
Critical questions remain unanswered: What magnitude of amyloid reduction constitutes a meaningful response? Should all patients receive follow-up PET, or only those with uncertain clinical response? How frequently should PET be repeated? The viewpoint does not propose specific thresholds but emphasises that these decisions must be informed by both emerging clinical data and resource availability in individual healthcare systems. Visit our health policy section to explore how different countries are implementing Alzheimer’s disease treatment frameworks.
Implications for Patients, Clinicians, and Healthcare Systems
What this means
Frequently asked questions
Why is amyloid PET becoming more important now?
The approval of disease-modifying anti-amyloid monoclonal antibodies (lecanemab and donanemab) has shifted Alzheimer’s disease from a condition managed diagnostically to one requiring active treatment monitoring. According to The Lancet eBioMedicine viewpoint, quantitative PET baseline measurements now support individual treatment decisions—determining whether to continue, switch, or discontinue therapy based on actual amyloid reduction in each patient.
Can amyloid PET predict which patients will benefit most from anti-amyloid therapy?
The viewpoint does not claim that baseline PET predicts individual response before therapy starts. Rather, it proposes that PET-guided follow-up imaging reveals whether an individual patient is actually responding to treatment. This distinction is important: baseline PET establishes the quantitative reference point, while serial PET scans document whether that burden is declining during therapy.
What are the practical barriers to implementing PET-guided treatment protocols?
Major barriers include limited PET scanner availability, cost, clinical workforce training, and the lack of consensus on optimal PET intervals and amyloid reduction thresholds for treatment decisions. The viewpoint acknowledges these constraints, emphasising that healthcare systems must develop protocols tailored to their own resources and patient populations.
The evolution from amyloid PET as a diagnostic tool to its role in treatment governance reflects a broader maturation of Alzheimer’s disease medicine. As anti-amyloid monoclonal antibodies become more widely available, healthcare systems will increasingly need to balance efficacy, safety (particularly the risk of ARIA), cost, and individual patient response. Amyloid PET imaging offers a quantitative foundation for these decisions, but only if clinical protocols are developed to use PET data systematically. Future research should define optimal PET imaging intervals, establish thresholds for treatment response, and test whether PET-guided protocols improve patient outcomes and resource efficiency compared to clinical assessment alone.
Source: From Target Engagement to Treatment Governance: The Evolving Role of Amyloid PET in Anti-Amyloid Therapy, The Lancet eBioMedicine, 2026
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