Hematological safety of hyperbaric oxygen therapy in oncology: Stratified analysis by chemotherapy and herbal medicine use.

Hyperbaric oxygen therapy (HBOT) is increasingly utilized as an adjunctive treatment in oncology; however, data on its hematological safety (particularly when combined with chemotherapy or traditional herbal therapies) remain limited. We retrospectively analyzed electronic medical records of adults with malignant neoplasms who received HBOT at Cha Ilsan Medical Center from July 1, 2022 to December 31, 2024. Safety was assessed via treatment-emergent adverse events graded by Common Terminology Criteria for Adverse Events and pre-post comparisons of 37 laboratory parameters. Subgroup analyses were stratified by chemotherapy and herbal therapy (traditional Korean medicine) exposure. Covariate-adjusted linear regression models were used to identify independent predictors of laboratory changes after false-discovery-rate correction. Among 259 patients undergoing 2692 HBOT sessions, 2 mild treatment-emergent adverse events occurred (0.07%); no serious or life-threatening events were observed. In 207 patients with paired laboratories, most hematologic and biochemical parameters were stable. Platelet count declined modestly (-16 × 103 µL-1; false-discovery-rate P < .001) and plateletcrit decreased (-0.01%; P < .001), with cohort means remaining within reference intervals. In the paired-laboratory cohort, chemotherapy exposure was 108 vs 99 unexposed, and herbal therapy (traditional Korean medicine) exposure was 132 vs 75 unexposed; exposures were not mutually exclusive. Subgroup analyses showed no clinically meaningful hematologic differences between exposed and unexposed groups. In multivariable linear models, chemotherapy was independently associated with lower white blood cell and neutrophil counts, and herbal therapy with a minor reduction in eosinophils; neither therapy was associated with platelet changes. Low-pressure HBOT demonstrates a favorable hematological safety profile in cancer patients, even when administered alongside chemotherapy or herbal therapies. These findings support the safe integration of HBOT into multimodal cancer care, although prospective multicenter trials are warranted to confirm long-term safety.