Protective effects of hydrogen gas inhalation on radiation-induced bone marrow damage in cancer patients: a retrospective observational study
Hirano SI, Aoki Y, Li XK, Ichimaru N, Takahara S, Takefuji Y. · Medical Gas Research. 2021;11(3):104–109.
Study at a glance
Human
Adults with end-stage cancer receiving intensity-modulated radiotherapy at Clinic C4 in Tokyo.
After each daily IMRT session, nasal-cannula gas was delivered inside a mild hyperbaric chamber at 1.35 atmospheres for 30 minutes. · 5% H₂ at 4 L/min inside the chamber; the article also expresses the pressure-adjusted exposure as equivalent to 6.8% H₂ at normal pressure.
Daily after IMRT for one to four weeks; radiation schedules ranged from 5 to 20 treatments.
White-cell and platelet ratios favored the H₂ group, but red cells, hemoglobin and hematocrit were not significantly different. Tumor response was similar between groups. Fatigue, depression, sleep and gastrointestinal quality-of-life measures were also similar and were not improved by H₂.
Very small, non-randomized retrospective comparison with unequal groups, heterogeneous cancers and substantial confounding risk. Registration and ethics approval were retrospective. The authors declared no conflicts and no financial support, yet the first author was affiliated with MiZ Co., Ltd. and MiZ personnel were thanked for writing advice; this apparent commercial connection is displayed despite the declaration.
What kind of evidence is this?
Human
Retrospective single-center observational comparison
Cancer research
Inhaled H₂
Information not yet classified
Some editorial classification fields are still pending. The source-reported outcomes and result are shown below; Hydrogenology does not infer a positive or negative signal from prose automatically.
Methods
Adults with end-stage cancer receiving intensity-modulated radiotherapy at Clinic C4 in Tokyo.
26 registered; three were excluded because IMRT was incomplete. The analysis included 23 patients: 16 in the H₂ group and 7 controls.
Daily after IMRT for one to four weeks; radiation schedules ranged from 5 to 20 treatments.
After each daily IMRT session, nasal-cannula gas was delivered inside a mild hyperbaric chamber at 1.35 atmospheres for 30 minutes.
H₂ diluted in air — H₂ as the experimental gas component, not Brown's gas.
5% H₂ at 4 L/min inside the chamber; the article also expresses the pressure-adjusted exposure as equivalent to 6.8% H₂ at normal pressure.
200 mL/min H₂, calculated from 5% of the reported 4,000 mL/min delivery flow.
Air was the carrier and control gas. No distinct O₂ intervention was reported; the article does not state a delivered O₂ percentage or O₂ flow, so neither is inferred.
Seven patients received air through the same cannula and chamber procedure after IMRT. Treatment was not randomized.
Outcomes and reported result
Ratios of red and white blood cells, platelets, hemoglobin and hematocrit before and after radiotherapy, tumor response and quality-of-life symptoms.
White-cell and platelet ratios favored the H₂ group, but red cells, hemoglobin and hematocrit were not significantly different. Tumor response was similar between groups. Fatigue, depression, sleep and gastrointestinal quality-of-life measures were also similar and were not improved by H₂.
The complete PMC article, supplementary patient table, exposure method, laboratory outcomes, tumor response, quality of life, funding and conflict statements were checked; favorable and null outcomes are both shown.
A reported association, difference or mechanism is not automatically a clinical benefit.
Limitations and applicability
Very small, non-randomized retrospective comparison with unequal groups, heterogeneous cancers and substantial confounding risk. Registration and ethics approval were retrospective. The authors declared no conflicts and no financial support, yet the first author was affiliated with MiZ Co., Ltd. and MiZ personnel were thanked for writing advice; this apparent commercial connection is displayed despite the declaration.
People with end-stage cancer receiving this clinic-specific IMRT and chamber protocol; it does not establish that H₂ prevents marrow toxicity in routine cancer care.
No single-study GRADE certainty rating is assigned. Read how records and evidence assessments are prepared.
Sources and record status
PMID: 33942780 · DOI: 10.4103/2045-9912.314329
Free full article on PubMed Central.
PubMed metadata and complete PubMed Central article with supplementary material; full-text and article-status check completed 8 August 2026.
10 August 2026
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