Radiopharmaceutical therapy has an appealingly precise premise: find a biological target, attach a radioactive isotope to a molecule capable of reaching it and irradiate the cancer while limiting exposure to healthy tissue. Yet when it comes to determining how much radiation an individual patient’s tumors and organs actually absorb, the field remains far less standardized than its precision-medicine label suggests.
That gap matters because the administered activity—the amount of radioactivity placed into the patient—is not the same as the absorbed dose delivered to a tumor or organ. Two patients receiving the same administered activity can process, distribute and eliminate a radiopharmaceutical differently. Their tumors may express different amounts of the target, their disease burdens may differ, and their kidneys, salivary glands, bone marrow and other organs may receive meaningfully different radiation exposures.
If radiopharma is going to become truly individualized, the industry must learn how to measure those differences consistently and use them to guide treatment. It cannot do that if every institution calculates absorbed dose differently, every scanner produces slightly different quantitative information and every software platform interprets the results through a different methodology.
A new initiative involving DOSIsoft Theranostics and the Foundation for the National Institutes of Health illustrates how seriously the field is beginning to take the problem. DOSIsoft has joined an FNIH Biomarkers Consortium project intended to harmonize quantitative imaging protocols and establish reliable absorbed-dose measurements for radiopharmaceutical therapy. The project is working toward consistent methods for SPECT/CT imaging and organ-level dose calculations, including more standardized approaches to acquisition, reconstruction, calibration and analysis.
This may sound like a technical exercise, but it is becoming foundational commercial infrastructure. Drug developers need comparable dosimetry data to evaluate dose-response relationships, select treatment regimens and design multicenter trials, while regulators need confidence that measurements submitted from different institutions mean the same thing. Hospitals need workflows that can be performed without turning every treatment into a research project, and physicians need results they can understand and use when deciding whether to continue, modify or stop treatment.
Software companies also need common inputs, definitions and validation standards. A beautifully designed dosimetry platform is of limited value if its output changes substantially depending on the scanner, reconstruction method, calibration procedure or segmentation practices used by each treatment center. The industry cannot build individualized treatment decisions on measurements that are precise within one institution but difficult to reproduce anywhere else.
There are understandable reasons why commercial radiopharmaceutical therapies began with standardized administered activities. Fixed regimens are easier to study, manufacture, schedule, prescribe and explain to regulators. They also reduce the operational burden placed on nuclear medicine departments that may not have the personnel, imaging capacity or software required to conduct patient-specific dosimetry. That practicality helped radiopharmaceutical therapy reach patients, but it should not automatically become the permanent endpoint.
External-beam radiation oncology has spent decades developing tools to plan the radiation dose delivered to tumors while protecting surrounding tissue. Radiopharmaceutical therapy distributes radiation internally and operates under different biological and logistical conditions, but the underlying question remains familiar: How much radiation reaches the target, and how much reaches the organs at risk?
Giving every patient the same administered activity may be operationally efficient, but it does not mean every patient receives the same treatment. Some may receive less radiation than their tumors could tolerate, potentially leaving therapeutic benefit unrealized, while others may approach organ limits sooner and face greater toxicity risks. Without reliable dosimetry, the industry has an incomplete view of both sides of that equation.
The challenge is not merely to calculate a number. It is to produce a number that remains meaningful across scanners, institutions, time points and treatment cycles. Quantitative dosimetry can be affected by when images are acquired, how many imaging sessions are performed, how scanners are calibrated, which reconstruction algorithms are used, how tumors and organs are segmented, and how time-activity curves are calculated. Each methodological choice can influence the final absorbed-dose estimate.
That variability becomes especially problematic in multicenter trials. If one hospital’s calculation cannot be confidently compared with another’s, researchers may struggle to identify dose-response relationships or establish organ toxicity thresholds. A therapy could generate valuable biological information in hundreds of patients while still failing to produce the standardized evidence needed to improve dosing for the next group.
This is why harmonization cannot be treated as a secondary academic concern. It directly affects clinical-development efficiency, regulatory evidence, physician confidence and the eventual value of dosimetry software. It could also determine whether patient-specific dosing becomes a practical commercial capability or remains concentrated within a small number of specialized academic institutions.
Standardization alone will not solve the adoption problem because dosimetry also has to fit inside real clinical operations. Many nuclear medicine departments are already managing workforce shortages, limited scanner availability and increasingly complex treatment schedules. A protocol that requires multiple lengthy scans, extensive manual segmentation and specialist interpretation may succeed at a major academic center but prove difficult to reproduce across a national treatment network.
The industry therefore needs methods that balance precision with practicality. Automation, artificial intelligence and improved quantitative imaging can reduce the burden, but only if those tools are validated against common standards. Faster calculations are useful, but faster calculations that cannot be reproduced will not give clinicians or regulators the confidence needed to change treatment.
Drug developers should also treat dosimetry as part of product development rather than something hospitals must solve after approval. Imaging schedules, analytical methods, software requirements and training programs should be considered alongside isotope supply, manufacturing, distribution and reimbursement. If personalized dosing is essential to a therapy’s long-term value, the infrastructure supporting it must be designed before commercial launch.
Radiopharma frequently presents itself as one of oncology’s most precise treatment modalities. In one sense, that is already true: molecular targeting can direct radiation toward cancer cells distributed throughout the body. But biological targeting is only one part of precision. The field must also be able to determine how much radiation reached those cells, how much reached healthy organs and whether the next treatment cycle should be the same as the last one.
The work being undertaken through the FNIH project will not immediately replace standardized treatment regimens with individually calculated prescriptions. What it can do is establish the common measurement framework required to test, validate and eventually scale that transition. That would give drug developers better evidence, provide regulators with more comparable information and help treatment centers adopt dosimetry without creating entirely new methods on their own.
Radiopharma does not need more vague promises about personalized therapy. It needs measurements clinicians can trust, regulators can evaluate and treatment centers can reproduce. Until absorbed dose means the same thing everywhere, individualized radiopharmaceutical therapy will remain more aspiration than standard practice.
