Chromatin diminution is a specialized developmental process in which a portion of the DNA is removed from the chromosomes of embryonic somatic-line cells. In C. kolensis , a zooplanktonic crustacean in the order Cyclopoida, the process occurs during the fourth cleavage division. Before this point, embryonic presomatic cells contain the same genome as the future germ line.

During diminution, somatic-line nuclei lose roughly 90% of their DNA, whereas germ-line cells retain their nuclear DNA unchanged throughout development. The study describes chromatin diminution as a marker of germline-soma differentiation and notes that the interphase before the diminution division is unusually long. The investigators designed the experiment to test whether nuclear activity is required to initiate chromatin diminution.

They reasoned that radiation could separate the effects of cytoplasmic determinants from the contributions of embryonic genes. Doses in the range used for nuclear inactivation were expected to produce chromosome aberrations while leaving enough cytoplasmic function for cleavage and other early developmental processes to continue. If nuclei were essential for launching diminution, extensive radiation damage should have prevented the process.

Instead, the observed survival of diminution under high doses supports a prominent role for factors already present in the fertilized egg’s cytoplasm. For the main irradiation experiments, the researchers used C. kolensis embryos at the four-cell stage, although some embryos at the two-cell stage received the highest dose. Irradiation was performed with gamma radiation at the Rokus-M facility of the Joint Institute for Nuclear Research.

Absorbed doses ranged from 5 to 200 Gy, delivered at a dose rate of 1.37 Gy per minute from a distance of 0.75 m. Embryos were examined 24 hours later. A mixture of ethanol and acetic acid was used for one hour of fixation, and aceto-orcein staining prepared the specimens for light microscopy.

The researchers counted blastomeres, inspected chromosome behavior during division and assessed micronuclei as indicators of chromosomal abnormalities. Data were processed using a t-test. The 5-Gy exposure produced a mixed developmental outcome.

Visible granules of eliminated chromatin indicated that diminution had occurred in all embryos irradiated at this dose. In the limited anaphases available for observation, the researchers recorded chromosome bridges, fragments and fused chromosomes. Thus, although this dose caused substantial chromosomal disruption, it did not prevent either the fourth cleavage division or the DNA-removal program that normally occurs during it.

At 20 Gy, approximately 41.0% of 307 embryos completed only one further division and reached the eight-cell stage, while 58.9% stopped at 16 cells after passing through the stage at which diminution normally occurs. Among 80 interphase figures assessed for micronuclei at the eight-cell stage, the mean was 1.14 micronuclei per cell, with a standard error of the mean of 0.35. A 100-Gy dose produced a similar developmental pattern: 64.5% of 353 embryos stopped at eight cells and 35.4% reached 16 cells.

The rare division figures again showed numerous bridges, chromosome fragments and adhering chromosomes. Although development failed, progression through the diminution stage indicated that nuclear damage did not suppress initiation of the process. The most extreme dose, 200 Gy, was administered to embryos at the two-cell stage, limiting direct comparisons with the lower doses that began at the four-cell stage.

Thirty-four percent of the 146 embryos stopped at the two-cell stage, apparently reflecting damage to cytoplasmic as well as nuclear structures. In 14 of 36 embryos, the usual signs of chromatin diminution were absent: researchers observed neither the expected abundance of eliminated-chromatin granules nor the sharp size difference between somatic-line cells before and after diminution. At this dose, chromosomes formed conglomerates that could not segregate normally during division.

Micronuclei were also observed in eight-cell embryos, and their mean number rose as radiation dose increased from 20 to 200 Gy. Across the 20–200-Gy treatments, irradiated embryos did not develop beyond the 16-cell stage, with some arresting earlier. The authors interpreted this pattern as evidence that early progression and the initiation of chromatin diminution are governed by a developmental program encoded in cytoplasmic determinants of the egg.

When nuclear function was lost, the embryo could nevertheless execute diminution before ceasing development. The comparison does not establish that nuclei are irrelevant to later morphogenesis: the numerous chromosomal aberrations could have blocked nuclear functions required for continued development. Rather, the results separate the apparently cytoplasm-driven initiation of diminution from the nuclear functions needed for subsequent embryonic growth.

A comparable phenomenon had previously been reported in the nematode Ascaris suum , whose embryos also undergo chromatin diminution. Irradiation of four-cell A. suum embryos prevented development beyond 16 cells, while radiation blocked the nuclear genome without suppressing chromatin diminution. The present study notes, however, that the earlier Ascaris experiment was not designed specifically to test diminution.

Its purpose was to examine radiation effects on early development. The newer experiment applies nuclear-inactivation logic directly to C. kolensis , adding evidence from a copepod whose diminution occurs specifically during the fourth cleavage division. The study has important measurement limitations.

The researchers did not systematically compare the frequency of chromosome aberrations across radiation doses using either anaphase analysis or micronucleus counts. Micronucleus counts were unavailable at the 16- and 32-cell stages after 20- and 100-Gy treatments because eliminated-chromatin granules obscured the micronuclei. The apparent dose-related increase in micronuclei was therefore described as a tendency rather than a completed quantitative analysis.

The highest dose was also applied at a different starting stage and damaged cytoplasmic components, so the absence of diminution in 14 embryos may reflect disrupted cytoplasmic organization rather than a direct requirement for nuclear function. The findings therefore support cytoplasmic control over initiation of diminution while identifying an extreme exposure in which damage beyond the nucleus can interfere with the process. Taken together, the results support the long-standing idea that early embryonic cytoplasm contains determinants capable of directing specialized developmental programs.

In C. kolensis , irradiation of nuclei did not generally cancel the somatic program that removes most of the genome during the fourth cleavage division, even though chromosomal damage stopped embryos from developing beyond the 16-cell stage. At 200 Gy, however, some embryos failed to show diminution, indicating that the process can also be disrupted when radiation damage extends beyond the nucleus. The experiment did not identify the individual cytoplasmic factors or establish whether they are proteins, RNAs or other molecules.

Its principal contribution is functional: it shows that severe nuclear inactivation alone is insufficient to prevent chromatin diminution in this copepod, while also revealing a high-dose condition in which disruption of cytoplasmic factors may interfere with the process.

Subject of Research: Experimental test of cytoplasmic control over chromatin diminution in the copepod Cyclops kolensis

Article Title: Study of chromatin diminution in Cyclops kolensis ( Copepoda , Crustacea ) by radiobiological methods

Article References: Grishanin, A., & Chinyakova, O. (2021). Study of chromatin diminution in Cyclops kolensis (Copepoda, Crustacea) by radiobiological methods. Comparative Cytogenetics, 15(4), 329-338. https://doi.org/10.3897/compcytogen.v15.i4.64350

Image Credits: AI Generated

DOI: 10.3897/CompCytogen.v15.i4.64350

Keywords: Chromatin diminution, Cyclops kolensis, Copepoda, Gamma radiation, Embryonic development, Genome reduction, Somatic differentiation, Cytoplasmic determinants, Chromosome damage, Radiobiology, chromatin, diminution

The modern story begins in the mid-1980s, when a series of papers challenged the assumption that radiation damage expressed itself only in the first divisions after exposure. Researchers demonstrated that lethal mutations and chromosomal aberrations could appear in distant progeny of irradiated cells, after many apparently normal divisions. Because the damage was lethal and non-clonal, it could not have been carried by the cells themselves; instead, the genome had become less able to eliminate or correct mistakes. This phenomenon is now known as radiation-induced genomic instability, or RIGI. The second pillar of NTE research came in 1992, when Nagasawa and Little exposed Chinese hamster ovary cells to such a low fluence of alpha particles that fewer than 1 percent of cell nuclei were directly traversed, yet sister chromatid exchanges appeared in roughly 30 percent of the population. Radiation-induced bystander effects, or RIBEs, were born: signals produced by irradiated cells could induce damage in unexposed neighbors.

Subsequent decades established the reality of bystander signaling using a suite of experimental protocols. Medium transfer experiments showed that culture medium harvested from irradiated cells could reduce the clonogenic survival of unirradiated recipients. Microbeam studies, in which single cells were targeted with counted particles, revealed that damage signals spread up to a millimeter away from the hit site. Transwell systems, in which irradiated and unirradiated cultures shared medium but not physical contact, confirmed that soluble factors were involved. Whole-animal models extended the phenomenon beyond the dish. Strikingly, the review documents that effects of this kind were recorded as early as 1968, when plasma from patients receiving X-ray therapy or total-body irradiation was shown to induce chromosomal aberrations in cultured lymphocytes from healthy donors, and again in 1977 with plasma from atomic bomb survivors. The phenomena were variously called indirect, abscopal, clastogenic or out-of-field effects, but all involved damage at sites in space or time that received no energy deposition.

How does a radiation hit in one cell produce DNA damage in another? The first mechanistic answer came from Little’s laboratory, which showed that gap junction intercellular communication, or GJIC, was involved in bystander signaling after alpha-particle irradiation. The inhibitor lindane suppressed the effect, and connexin proteins forming the junctions were upregulated in cultures exposed to ultra-low fluences. But GJIC could not explain medium transfer experiments, where the signal survived in culture medium for hours. The leading explanation there involved reactive oxygen species and reactive nitrogen species generated by direct irradiation, which induced secondary damage in surrounding cells. Yet ROS and NOS are short-lived, so they too could not fully account for medium transfer, which triggers apoptosis, calcium release, mitochondrial membrane depolarization and caspase activation in recipients. The review notes that no single magic factor was ever characterized; some experiments from the authors’ group suggested the bystander effect might actually arise from a loss of factors rather than active secretion, with serotonin naturally present in serum bound by irradiated cells and triggering downstream calcium release in recipients.

Mitochondria have emerged as central players in this signaling web. Lyng and colleagues reported mitochondrial membrane depolarization as a robust marker of bystander signaling, and altered energy production was documented in both targeted and non-targeted cells. Nugent and colleagues measured direct effects on mitochondrial DNA and increased mitochondrial mass in cells with functionally compromised mitochondria after both direct gamma radiation and bystander factors. A particularly striking line of work from the McMaster group established a connection between mitochondrial complex 1 function and radiation-induced UVA biophoton emission from directly irradiated cells. This ultraweak ultraviolet emission proved both necessary and sufficient to produce bystander effects in unirradiated cells held in separate flasks with no medium contact. In parallel, other researchers showed that irradiated cells release exosomes containing miRNAs and even mitochondrial DNA that can communicate information to bystander cells. Reconciling the two hypotheses, Le and colleagues extracted exosomes from cultures that had sat above tritium-irradiated flasks, where beta tracks could not reach them, and demonstrated that the purified exosome fraction induced mitochondrial damage and reproductive cell death in a completely separate set of cells, but only when UVA photons had not been blocked by a yellow cellophane filter.

Perhaps the most provocative claim in the review is that NTEs, long measured using endpoints seen as bad at the level of the individual cell, are actually protective. Bystander signaling can induce adaptive responses, in which signals from irradiated cells prime unirradiated neighbors to resist subsequent genotoxic insults through enhanced DNA repair, altered cell-cycle regulation, antioxidant responses and elimination of damaged cells by apoptosis. The review links this to the phenomenon of low-dose hypersensitivity and induced radioresistance, or HRS/IRR, a dose-response pattern in which cells show a steep response below about 100 mGy followed by a plateau and a shallower curve above roughly 0.5 Gy. Joiner’s group attributed the transition to a threshold dose above which DNA repair becomes inducible, involving PARP and ATR signaling. Collaborative experiments showed that bystander effects could be demonstrated in the HRS region of the dose-response curve but were neutralized when the dose applied in the bystander assay fell in the IRR range, suggesting that RIBE is a low-dose phenomenon that can be counteracted if DNA repair is induced, and that it may account for part of the enigmatic shoulder of the classical survival curve.

Dose and dose rate studies sharpen the picture. Experiments by the authors’ group and Prise’s group determined that NTEs are triggered by very low doses, around 2 to 3 mGy of low-LET radiation, and appear to saturate above 0.5 Gy. A survival curve reconstructed over seven log cycles of dose showed three distinct phases: below 2 mGy no bystander effect, between 2 and 500 mGy no difference between directly irradiated cells and cells receiving irradiated-cell conditioned medium, and above that a clear divergence where directly irradiated cells followed the classic dose response while medium-transfer cells showed no further increase in reproductive death. The calcium spike that Lyng identified as the first sign of bystander signaling was detected only when conditioned medium came from cells receiving 2 mGy or more, indicating a mechanistic threshold. Radiation quality adds further nuance: alpha particles, X-rays and gamma rays all produce bystander effects and genomic instability, but the evidence suggests that pure neutrons, when the gamma contamination is shielded out, do not produce NTE at low doses, a conclusion supported by zebrafish experiments in which robust gamma bystander signaling occurred but neutron exposure produced no effect.

Critics once dismissed NTEs as artifacts of cell culture, but the review assembles ample in vivo evidence. Cross-sex bone marrow transplant studies in mice demonstrated transmissible chromosomal instability in regenerating marrow. Abscopal effects in lung tissue after radiotherapy showed in vivo bystander responses, with the immune system implicated by Demaria and others. Bystander effects were found in serum from Chernobyl-affected populations as long as 20 years after the reactor explosion, and multigenerational genomic instability was documented in bank voles in the Belorussian Polessky reserve. Russian researchers showed that irradiated mice produce volatile signals causing chromosomal damage in unirradiated littermates, and the McMaster group extended inter-animal signaling to fish, earthworms, crickets and mice. Proteomic analysis of bystander fish revealed a protective proteome enriched in antioxidant and DNA repair proteins, which the directly irradiated fish conspicuously lacked, reinforcing the view that NTE signaling functions as an early-warning system coordinating population-level responses.

The implications ripple outward in several directions. For radiotherapy, especially new modalities such as FLASH protocols using ultra-high dose rates, out-of-field and abscopal effects raise questions about how bystander signaling plays out during treatment planning, and whether signals from the tumor ecosystem, including fibroblasts, immune cells and endothelial support vessels, could be exploited as biomarkers or therapeutic targets based on mitochondrial metabolism, the apoptotic cascade or serotonin receptors. For radiation protection, the review argues that NTEs are relevant to low-dose and chronic exposures because they involve signaling between and within populations of species in ecosystems, coordinating adaptation and evolution, concepts such as resilience, adaptation and historic dose. In the human protection field, however, BEIR and UNSCEAR reports merely suggest that no conclusions can be drawn about the relevance of NTE at this time. The authors conclude that imaging and therapy would both benefit from greater mechanistic understanding of NTE, and that these communication mechanisms are likely to be highly relevant to population responses to low-dose radiation at the level of cell, tissue and organism signaling.

Subject of Research: Non-targeted effects of radiation and DNA damage signaling

Article Title: Non-targeted effects and DNA: vulnerabilities at the interface

Article References: Mothersill, C., Rusin, A., & Seymour, C. (2026). Non-targeted effects and DNA: vulnerabilities at the interface. Frontiers in Oncology, 16, Article 1952660. https://doi.org/10.3389/fonc.2026.1952660

Image Credits: AI Generated

DOI: 10.3389/fonc.2026.1952660

Keywords: radiobiology, bystander effect, DNA repair, non-targeted effects, genomic instability, radiotherapy, radiation protection, mitochondria, exosomes, adaptive response, Non-targeted, effects

The study, published in the Journal of Translational Medicine, comes from a group led by Jingyuan Liu and Yang Liu at the Department of Radiotherapy of the Affiliated Cancer Hospital of Zhengzhou University and Henan Cancer Hospital, with collaborators at the same institution and at Zhengzhou University’s First Affiliated Hospital. Their central finding is deceptively straightforward. In mouse models of non-small cell lung cancer liver metastasis, a prophylactic dose of just 2 Gray, delivered to the liver before metastatic challenge, significantly suppressed metastatic colonization. Among the doses tested, 2 Gy showed the strongest antimetastatic effect, a dose low enough that it causes minimal tissue damage yet high enough to fundamentally alter how the liver communicates with the immune system.

What makes this result remarkable is the mechanism behind it. Radiation therapy is conventionally understood as a cytotoxic tool, a way of killing tumor cells with focused beams of high-energy photons. But over the past two decades, radiobiologists have come to appreciate that radiation does far more than damage DNA. At low doses, it can reprogram the behavior of cells in the irradiated field, altering the signals they send to immune cells. The Zhengzhou team set out to test whether such immune modulation could be harnessed prophylactically, not to destroy tumor cells directly, but to make the liver a hostile landing ground for them.

To answer this question, the researchers combined an unusually broad set of tools. They used bulk RNA sequencing to survey gene expression across irradiated liver tissue, single-cell RNA sequencing to resolve which individual cell types were responding, and in vitro functional assays to test the signaling pathways they uncovered. Finally, they performed in vivo neutralization experiments, blocking a key molecule with antibodies in living animals to confirm that the mechanism they had identified was genuinely responsible for the antimetastatic effect. This layered approach allowed them to trace a complete signaling chain from hepatocytes, the main functional cells of the liver, all the way to the recruitment of cytotoxic immune cells.

The chain begins with hepatocytes. When the liver received its 2 Gy dose, the team found that hepatocytes increased their production of serum amyloid A1, or SAA1, a protein more commonly associated with inflammatory responses. SAA1 then acted on a specific population of immune cells residing in or recruited to the liver: inflammatory monocytes. These monocytes, which in the context of an unprepared pre-metastatic niche can be co-opted by tumors to suppress immunity and scaffold metastatic growth, were instead pushed in a fundamentally different direction by the irradiation-induced signal.

At the molecular level, SAA1 engaged Toll-like receptor 2, a pattern-recognition receptor best known for detecting microbial components, on the surface of the monocytes. Engagement of TLR2 activated a transcriptional program driven by the NF-κB pathway, specifically through its RELA subunit, a master regulator of inflammatory gene expression. The consequence of this activation was the upregulation of SLC7A11, a solute carrier protein that imports cystine into cells and is a central component of cellular antioxidant defenses. With SLC7A11 activity elevated, the monocytes achieved improved redox homeostasis, a better-balanced internal oxidative state that allowed them to sustain a new functional identity.

That identity was chemokine-secretory. The reprogrammed monocytes became robust producers of CXCL10, a chemokine with a well-established role in attracting cytotoxic immune cells. In the irradiated liver, CXCL10 served as a beacon, drawing CD8-positive T cells, the principal killer lymphocytes of the adaptive immune system, into the tissue that tumor cells would soon attempt to colonize. When circulating lung cancer cells arrived, they encountered a liver patrolled by an alert cytotoxic army rather than one paved with immunosuppressive stromal support. The pre-metastatic niche had been flipped from pro-metastatic to anti-metastatic.

The team did not stop at correlation. To prove that CXCL10 was functionally required for the protective effect, they neutralized the chemokine in irradiated animals. The result was decisive: blocking CXCL10 reduced the recruitment of CD8-positive T cells to the liver and attenuated, though did not necessarily abolish, the antimetastatic benefit of low-dose irradiation. This loss-of-function experiment anchors the entire mechanistic model. Without the chemokine signal, the reprogrammed monocytes lose their ability to summon cytotoxic T cells, and the liver reverts toward vulnerability. SLC7A11, meanwhile, was shown to be required to sustain the chemokine-secretory phenotype itself, placing the antioxidant transporter upstream of CXCL10 production in the causal chain.

The translational implications are considerable. Liver metastasis from lung cancer is a major driver of mortality, and current strategies for preventing it are limited. Immune checkpoint blockade has transformed outcomes for some patients with non-small cell lung cancer, but hepatic metastases are notoriously resistant to immunotherapy, in part because the liver’s immune environment is inherently tolerogenic. A prophylactic intervention that remodels the hepatic immune landscape before tumor cells arrive could, in principle, complement existing approaches. The dose involved, a single 2 Gy fraction, is far below the levels used for ablative radiotherapy and is comparable to fractions routinely delivered in palliative settings, suggesting that toxicity would be manageable, though this remains to be demonstrated in patients.

Caution is warranted. The findings come from mouse models, and the authors note that the published version is an early-release, peer-reviewed accepted manuscript subject to further editorial processing. The retrospective clinical component of the study was approved by the Ethics Committee of the Affiliated Cancer Hospital of Zhengzhou University and Henan Cancer Hospital, and the animal work followed ARRIVE guidelines, but no prospective human trial data yet exist. Irradiating a healthy liver prophylactically raises legitimate questions that only clinical studies can answer, including optimal timing, patient selection, and long-term hepatic safety. Still, the study opens an intriguing frontier in what the authors describe as low-dose immune radiobiology: the idea that radiation, at doses far too low to kill tumor cells, can be deployed as an immune sculpting tool. If the hepatocyte-to-monocyte-to-CXCL10 axis identified here holds up in humans, a single low-dose treatment could one day help keep the liver off the map of metastatic destinations for lung cancer patients.

Subject of Research: Prophylactic low-dose liver irradiation reprogramming the pre-metastatic immune niche to suppress non-small cell lung cancer liver metastasis

Article Title: Prophylactic low-dose liver irradiation reprograms the pre-metastatic immune niche and suppresses NSCLC liver metastasis

Article References: Liu, J., Zhang, T., Zhu, X., Lan, Z., Li, L., Yang, Y., Wang, Q., Sun, Z., & Liu, Y. (2026). Prophylactic low-dose liver irradiation reprograms the pre-metastatic immune niche and suppresses NSCLC liver metastasis. Journal of Translational Medicine. https://doi.org/10.1186/s12967-026-08883-8

Image Credits: AI Generated

DOI: 10.1186/s12967-026-08883-8

Keywords: low-dose irradiation, pre-metastatic niche, liver metastasis, NSCLC, SAA1, TLR2, NF-kappaB, SLC7A11, CXCL10, inflammatory monocytes, CD8 T cells, radiobiology

The motivation is not academic. In a structured workshop where radiation oncologists, medical physicists, and technologists applied the same radiobiological models to the same standardized cases, mean agreement between practitioners reached only 25.8 percent on a Jaccard index, dropping to 10 percent for head-and-neck cases. Proposed dose-per-fraction adjustments for identical clinical situations ranged from 1.8 to 2.5 Gy, and nearly half of the surveyed centers reported they could not compute biologically equivalent schedules with the tools available to them. Multi-center studies of reirradiation have reached the same conclusion from another direction: variation in how centers scale radiobiological dose introduces clinically relevant differences in cumulative dose estimates.

Part of that dispersion reflects disagreement about vocabulary rather than radiobiology. Identical parameters yield substantially different reported EQD2 values depending on whether proliferation losses are applied to the evaluated schedule only or symmetrically to both the evaluated and the reference schedule. Three modeling elements are routinely omitted. First, the classic linear-quadratic model is widely held to overestimate cell kill at the large fraction sizes used in stereotactic treatments, so the linear-quadratic-linear form of Astrahan replaces the quadratic term with a straight line above a transition dose. Second, overall treatment time matters, because accelerated proliferation of surviving tumor cells after a kick-off time consumes dose every day, meaning an interruption is never neutral. Third, when two fractions are given in a single day, the incomplete-repair correction of Thames applies, since the second fraction arrives before sublethal damage has fully repaired.

The new release is a reimplementation of a validated 2014 MATLAB application, rebuilt as a dependency-free Python library and a browser application. The original was a Windows executable requiring a several-hundred-megabyte MATLAB runtime, with an interface in French and 3,567 lines of source in which the entire calculation sat inside a single callback. It could not be inspected, cited by version, or run by a colleague during a meeting. Version 3.0 separates the model, the calendar conversion, and a library of radiobiological tissue parameters into an auditable core that depends only on the Python standard library. The delivery layer embeds the sources into a single HTML page of about 112 kilobytes that runs the model locally in each visitor’s browser using WebAssembly, with no computation on a server, no analytics, and no forms.

The mathematics is deliberately complete. Each tissue carries seven parameters, including the alpha/beta ratio, a transition dose above which the response becomes linear, a repair half-time, and a kick-off time and doubling time for proliferation. The software computes biologically effective dose with the linear tail, subtracts proliferation losses once overall time exceeds the kick-off time, applies the incomplete-repair correction for twice-daily fractions, and then solves for the number of reference fractions carrying the same biological effect. Crucially, the reference schedule carries its own overall time and therefore its own proliferation loss, a point the authors identify as accounting for most disagreement between implementations. Treatment calendars run five days a week, weekends included, because cells do not rest on Saturdays, and successive courses are matched against one continuous reference schedule rather than restarting the clock each time.

Verification proceeded in two distinct steps. The first asked whether the calculation was transcribed correctly from MATLAB to Python: replaying 4,438 treatment schedules through the original 2014 program and the new library produced 69,131 compared values, of which 99.991 percent agreed at the reference’s own six-digit precision, with a largest single deviation of 0.04 Gy and every one of 34,403 paired equivalent doses clearing a pre-set tolerance of 0.05 Gy. The second step checked the equations against closed forms independently of the old code. The authors are careful to state that neither check constitutes clinical validation; both establish fidelity and correctness of the arithmetic.

One change between releases genuinely moves results. The 2014 code charged elapsed treatment time twice, once inside the equivalence equation at a flat rate and once afterward using the real calendar, which inflated organ doses for protracted schedules. Version 3.0 charges time once, on the calendar throughout. The magnitude is striking: for 60 Gy delivered at 12 Gy per fraction, the old treatment overstated lung equivalent dose by 74 percent, against 28 percent for the correct single charge. At the reference fraction size of 2 Gy the effect vanishes, and below it the sign reverses, with protracted schedules losing dose rather than gaining it. Four smaller defects of the old release, including a division by zero that reported complication probability as 100 percent for five tissues, were also fixed and documented rather than silently corrected.

External coherence checks place the tool against landmark trials. Against 78 Gy in 39 fractions, the software puts the ultra-hypofractionated arm of the HYPO-RT-PC prostate trial at 77.94 Gy, and it orders the two hypofractionated arms of CHHiP as the trial did. It disagrees with PROFIT, placing 60 Gy in 20 fractions 5.5 Gy below the conventional arm that demonstrated non-inferiority, but that gap closes when the alpha/beta ratio is set to 1.5 Gy, near the pooled clinical estimate of 1.4 Gy, evidence that the tabulated default of 3.1 Gy is not universal. On the normal-tissue side, the tabulated Lyman parameters fail outright for the spinal cord, returning a 5.1 percent complication probability where QUANTEC puts the risk near 0.2 percent, a discrepancy the authors report plainly.

The limitations are stated with unusual candor. This is a model comparison tool, not a treatment planning system: it knows nothing of dose distributions, volume effects, or plan constraints, and the authors explicitly warn that its outputs must not be used to choose or modify a prescription, compute compensation for a real interruption, sum dose in a reirradiation decision, or predict outcomes for an individual patient. The tumor control probability, newly exposed in this release, has not itself been validated against clinical outcome, and parameter uncertainties frequently exceed the differences the software displays, which is why it offers an alpha/beta sensitivity band and declines to name a best schedule when uncertainty bars overlap. Its purpose is comparing schedules under a stated model, seeing how the comparison moves when assumptions move, and teaching why.

The impact may ultimately lie in access and traceability. In a field where nearly half of surveyed centers report no usable tool, removing the installation barrier is the difference between a model being applied and being skipped. Every parameter’s provenance is recorded, the historical 2014 behavior remains reachable so that older published results can be reproduced, and the validation dataset ships with the code. A version-pinned, openly inspectable implementation that every participant in a multi-center study can run in a browser removes one term from the variance between centers, separating disagreement over arithmetic from the genuine scientific disagreement over parameters. A correction pushed to the repository goes live in browsers within a minute, and every version stays citable by its own DOI, an ambition the authors state explicitly: to give every department something independent against which to check a commercial planning system’s answer.

Subject of Research: Open-source software for biologically equivalent dose calculation in radiotherapy fractionation

Article Title: LQL-Equiv-web: a Python library and browser application for linear-quadratic-linear dose equivalence in radiotherapy

Article References: Voyant, C., & Julian, D. (2026). LQL-Equiv-web: a Python library and browser application for linear-quadratic-linear dose equivalence in radiotherapy. SoftwareX, 36, Article 103085. https://doi.org/10.1016/j.softx.2026.103085

Image Credits: AI Generated

DOI: 10.1016/j.softx.2026.103085

Keywords: radiotherapy, dose equivalence, EQD2, linear-quadratic model, hypofractionation, radiobiology, open-source software, WebAssembly, Python, treatment interruptions, reirradiation, tumor control probability