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SIRiiM

The International Society for Radiation Immunity and Immuno-Modulation (SIRiiM) exists because a failed pandemic trial exposed a real and largely unstudied question: what does radiation do to the immune system at doses far below those used to treat cancer?

On this page
How it began — the COVID-19 episode What the failure revealed Why a society, rather than more single studies The questions on the table SIRiiM References

How it began — the COVID-19 episode

In 2020, with critical-care capacity overwhelmed and no specific therapy, clinicians revived an idea from the pre-antibiotic era and irradiated the lungs of patients with severe COVID-19 pneumonia. The reasoning was not fanciful. Low-dose radiation had a documented anti-inflammatory effect, and the illness killing these patients was an inflammatory one. Trials opened worldwide, and a joint National Cancer Institute, NCRP and NIAID workshop convened to set a framework for conducting them — declining, pointedly, either to endorse or refute the approach1.

The specific application did not work. A randomised, double-blind trial in ventilated patients found no difference in ventilator-free days and identical 28-day survival — 63.6% in both arms2, despite encouraging single-arm and matched-control results that preceded it3. That is the honest record, and SIRiiM was not founded to dispute it.

What the failure revealed

What the episode did was put several hundred radiation oncologists, radiobiologists, immunologists and intensivists in the same conversation for the first time — and the question that survived the trial was larger than the trial.

The immunomodulatory effect of low-dose X-irradiation is not speculative. It has been characterised across leukocyte–endothelial adhesion, adhesion-molecule and cytokine expression, apoptosis induction, and the behaviour of macrophages and polymorphonuclear cells — and, strikingly, it is not linear. The effect peaks somewhere around 0.3–0.7 Gy, a window empirically identified in clinical practice long before the mechanism was described, and falls off on either side4.

A discontinuous dose–response is a signal that something specific is happening, not a smooth toxicological gradient. Related work on the radiation adaptive response spans oncology, neurodegenerative disease, pandemic response and space medicine — and reaches the same conclusion each time: the phenomenon is real, the mechanism is incompletely elucidated, and the field lacks standardised protocols5.

That is the paradigm that dawned during the COVID trials. If immuno-modulatory radiation acts through identifiable immune pathways, then its plausible reach is not one virus. It is every disease in which those pathways are deranged — a set that is largely unmapped.

Why a society, rather than more single studies

The COVID episode also demonstrated the failure mode. Dozens of small, uncontrolled, differently-designed studies produced encouraging results that a single properly randomised trial did not reproduce. The problem was not enthusiasm; it was the absence of shared protocols, agreed endpoints, dose conventions and a venue for publishing negative results.

SIRiiM was formed to supply that: concerted, standardised, sceptical study of radiation immunity and immuno-modulation, so the next promising indication is tested properly the first time rather than re-learned the hard way. Its partnership with the CureRays Innovation & Education Institute runs through IJRM-SSS, the Institute’s journal, which SIRiiM co-publishes.

The questions on the table

  • Dose. Why the response peaks near 0.3–0.7 Gy, and whether that window is the same across tissues and diseases.
  • Mechanism. Which immune pathways carry the effect, and whether it can be produced or blocked pharmacologically.
  • Indication. Which inflammatory and immune-mediated conditions have a risk–benefit arithmetic that could justify irradiating a non-malignant disease at all.
  • Risk. The radiogenic risk that any benign-disease indication must be weighed against, over the decades in which it would appear.
  • Method. Shared protocols, endpoints and reporting standards — the thing whose absence made the COVID literature so hard to interpret.

SIRiiM

The society maintains its own site and membership. The Institute does not speak for SIRiiM, and nothing on this page should be read as its official position.

Visit siriim.org IJRM-SSS, the joint journal

References

  • Prasanna PG, Woloschak GE, DiCarlo AL, et al. Low-dose radiation therapy (LDRT) for COVID-19: benefits or risks? Radiat Res. 2020;194(5):452–464. doi:10.1667/RADE-20-00211.1
  • Papachristofilou A, Finazzi T, Blum A, et al. Low-dose radiation therapy for severe COVID-19 pneumonia: a randomized double-blind study. Int J Radiat Oncol Biol Phys. 2021;110(5):1274–1282. doi:10.1016/j.ijrobp.2021.02.054
  • Sanmamed N, Alcantara P, Gómez S, et al. Low-dose radiation therapy in the management of COVID-19 pneumonia (LOWRAD-Cov19). Radiother Oncol. 2022;171:25–29. doi:10.1016/j.radonc.2022.03.015
  • Rödel F, Frey B, Manda K, et al. Immunomodulatory properties and molecular effects in inflammatory diseases of low-dose x-irradiation. Front Oncol. 2012;2:120. doi:10.3389/fonc.2012.00120
  • Kanani A, Krasowska J, Fornalski KW, et al. Adaptive response: a scoping review of its implications in medicine, space exploration, and beyond. Dose Response. 2025;23(3). doi:10.1177/15593258251360051
  • Reichl B, Block A, Schäfer U, et al. DEGRO practical guidelines for radiotherapy of non-malignant disorders: part I. Strahlenther Onkol. 2015;191(9):701–709. doi:10.1007/s00066-015-0865-8