Radiopharmaceutical therapy is growing fast.
Dosimetry infrastructure is not keeping up.

Somatostatin receptor therapy and PSMA-targeted therapy have shown what targeted radionuclide therapy can achieve when science and infrastructure are aligned. The field is now expanding rapidly — more agents, more trials, more nuclides, more sites. What has not kept pace is dosimetry: the capacity to calculate, document, and act on patient-specific absorbed dose in a way that is accurate, reproducible, and compliant with what regulators now expect. That gap is the subject of this article.

The dosimetry gap

The therapy is growing. The number of clinical trials is growing. The number of approved agents is growing. But the number of nuclear medicine departments with genuine dosimetry capability — qualified staff, validated software, documented methods, regulatory-grade output — has not grown at the same rate.

The nuclide list is also lengthening rapidly:

Each of these nuclides has different physical properties — half-life, emission type, tissue range — that determine how dosimetry must be performed. There is no single protocol that transfers cleanly from one to another. This is not a problem that gets easier as the field broadens. It gets harder.

In clinical routine, the consequence is that individualised dosimetry — which should inform how a patient's subsequent cycle is planned, whether dose is escalated, whether organs at risk are being protected — is often skipped because there is no infrastructure to do it. A fixed administered activity is used instead. That may be acceptable in some settings. In others, it is a missed clinical opportunity.

In clinical trials, the consequence is more acute. Dosimetry is not optional — it is often a primary or secondary endpoint. If the data are not collected correctly from the start, or if methods vary across sites, the dataset cannot support a regulatory submission. And a dosimetry gap discovered at the analysis stage is one that cannot be closed by going back.

What the EMA is now formally requiring

The regulatory picture in Europe has sharpened considerably. In October 2024, the EMA's Committee for Medicinal Products for Human Use (CHMP) published a Concept Paper — reference EMA/CHMP/451705/2024 — on the clinical evaluation of therapeutic radiopharmaceuticals in oncology. Public consultation closed in January 2025. A multi-stakeholder workshop followed. A full guideline is in preparation.

The Concept Paper is not a draft guideline yet. But it is a clear statement of direction, and the direction is unambiguous: the EMA intends to make dosimetry a formal, specified requirement within the clinical development framework for therapeutic radiopharmaceuticals — not a recommendation, not best practice, but a structured expectation with defined data standards.

This matters for two distinct reasons. First, it closes off the ambiguity that some sponsors have operated within — the sense that dosimetry is important but its exact scope and format in a submission is negotiable. Once the guideline is finalised, there will be a defined standard. Submissions that do not meet it will face questions that cannot be answered retrospectively.

Second, it connects regulatory requirements to clinical practice in a way that is new. The EMA is explicit that the purpose of requiring dosimetry data in a marketing authorisation dossier is to generate the information that appears in the Summary of Product Characteristics — the SmPC — and that clinicians then use to make individualised treatment decisions. In other words, dosimetry in a clinical trial is not just a data collection exercise. It is the source of the information that makes individualised therapy possible for every patient treated after approval.

There is also a transatlantic dimension. The FDA issued its own draft guidance on radiopharmaceutical development in the same period. The two documents share the broad objective — appropriate dose justification and patient safety — but differ in specifics: the weighting given to dosimetry data versus clinical toxicity measures, the required duration of long-term safety follow-up, and aspects of trial design. Sponsors developing assets for both markets need to navigate both frameworks, and the differences have real cost and timeline implications if not identified at the protocol stage. Oncosia has direct experience supporting both FDA-facing and EMA-facing dosimetry work, and can help identify where requirements converge and where they diverge.

For sponsors currently in Phase I or Phase II, the practical implication is straightforward: design dosimetry into your trial now, to a standard that will survive the guideline that is coming. The worst position to be in is to complete a pivotal trial with dosimetry data that was collected, but not collected in a way that meets the expectation that will be applied at the point of submission.

Alpha therapy — the next frontier

Much of the current clinical conversation focuses on Lu-177-based beta emitter therapy. That is appropriate — it is the most widely deployed modality in targeted radionuclide therapy and the anchor of the most successful approved agents. But the pipeline is already shifting.

Targeted alpha therapy — Ac-225, Pb-212, At-211, Bi-213 — offers a fundamentally different radiobiological profile. High linear energy transfer over a very short path length produces cytotoxicity at the cellular level with less off-target exposure. The implications for patient selection, dosing strategy, and dosimetry methodology are significant.

Alpha dosimetry is genuinely more demanding than beta dosimetry. The physical properties of alpha emitters are less forgiving of errors in acquisition timing or image quantification. The absence of established clinical standards — comparable to the EANM Dosimetry Committee guidance for beta emitters — means that methods must be carefully justified and documented. This is not a barrier that better software alone solves. It requires expertise grounded in the underlying physics.

Oncosia is engaged with alpha dosimetry as the field develops. If you are designing a trial with an alpha-emitting agent, dosimetry planning should begin at the protocol stage — not at the point where the first patient is enrolled.

What this means for clinical trial sponsors

A sponsor building a Phase II or III radiopharmaceutical trial faces a dosimetry challenge that is structural rather than incidental. The core question is not which software to use — it is how to generate consistent, auditable, GCP-compliant dosimetry data across fifteen or forty clinical sites, each of which may have different scanners, different local workflows, and different levels of dosimetry experience.

Getting the approach right early is the key. Dosimetry that is defined at the protocol stage — before recruitment begins — avoids the amendments, data harmonisation challenges, and methodology questions that arise when it is addressed later. And a centralised model, where one team applies one methodology across every site from the first imaging visit, is the most reliable way to ensure the dataset holds up at submission.

That is what Oncosia provides for clinical trials: one team, one methodology, one reporting standard, applied consistently across every site and every patient.

1. 01 Protocol-stage integration Dosimetry requirements are defined before recruitment begins — acquisition timing, image analysis method, nuclide-specific considerations, reporting format. This eliminates the protocol amendment problem.
2. 02 Site-agnostic execution Sites send anonymised SPECT/CT imaging data. Oncosia performs all analysis centrally, using validated software and documented methodology. No new equipment is required at the site.
3. 03 GCP-compliant reporting Every report is audit-ready. Methodology is referenced to EANM Dosimetry Committee guidelines. Documentation is structured for FDA and EMA submission requirements.
4. 04 Managed rental equipment Where a site does not have adequate SPECT/CT capability, Oncosia can arrange calibrated rental equipment — covering acquisition, not just analysis.

What this means for nuclear medicine departments

For a hospital nuclear medicine department beginning to administer somatostatin receptor or PSMA-targeted therapy in routine practice, the question is increasingly not whether dosimetry matters — it is how to implement it without adding overhead that the department cannot sustain.

Professional associations including EANM and SNMMI are actively working to raise qualification standards and support departments in building dosimetry capability. The direction of travel is clear. The practical challenge is that building a full dosimetry infrastructure alongside a new therapy pathway takes time, staff capacity, and investment in validated software and quality documentation — resources that are genuinely constrained in most departments.

Oncosia's Dosimetry as a Service (DaaS) model addresses this directly. The department acquires SPECT/CT images on its own scanner, following the protocol Oncosia provides. Anonymised data are transferred to Oncosia. Analysis, calculation, and reporting are handled centrally. The department receives a complete absorbed dose report — organ-level and, where relevant, tumour-level — within five working days.

This is not a compromise. It is what a rigorous dosimetry process looks like when it is built by people who do it every day, using validated methods, with the software and the expertise already in place.

The growth trajectory — and what it demands

The numbers confirm the direction. Multiple market analyses place the global radiopharmaceutical therapy market on a trajectory to double in value before 2034, with annual growth above 7%. Active therapeutic trials have grown from a handful in 2018 to more than eighty today. And a wave of major acquisitions — BMS, AstraZeneca, Eli Lilly — confirms that the pharmaceutical industry has placed a clear strategic bet on targeted radionuclide therapy as a defining oncology modality for the decade ahead.

What growth at this scale demands is infrastructure. Not just isotopes and targeting vectors — those conversations are already well established — but the dosimetry function that sits at the centre of every treatment decision and every trial endpoint. That gap is narrowing, but it has not closed. The field's ambition has consistently outpaced its dosimetry capacity, and the regulatory and clinical consequences of that mismatch are now becoming visible.

Behind every dose calculation, a patient

Every absorbed dose calculation corresponds to a patient. The dose they receive shapes whether therapy works, whether organs are protected, whether the next cycle is adjusted. Getting it right is not a technical nicety — it is the point of the exercise.

The tools to get it right now exist: validated software, EANM-referenced methodology, experienced teams who specialise in this work. What Oncosia provides is the infrastructure that makes those tools accessible — at the department level, at the trial level, and across the full range of therapeutic nuclides the field is deploying. Because the dosimetry needs to be done well, for every patient.