Hyperbaric oxygen therapy (HBOT) can reduce pain and fibrosis in women with local toxicity following breast radiotherapy, a US study suggests.

Investigators from the HONEY trial invited 125 women experiencing late local toxic effects from breast irradiation – moderate or severe breast, chest wall, and/or shoulder pain alongside at least one symptom of mild/moderate/severe fibrosis, breast oedema, and/or movement restriction – to undergo HBOT, and randomised 61 women to a control arm.

One-quarter of invited patients (n=31) underwent treatment with the intervention, which involved patients breathing 100% oxygen during four intervals of 20 minutes in a two-hour session, for 30 to 40 sessions in total over six to eight weeks.

In the intent-to-treat (ITT) population, moderate or severe pain at follow-up was reported in 50% of the intervention arm and 62% of the control arm (OR 0.63; p=0.18), and as such, the primary endpoint was not reached, according to results published in JAMA Oncology (link here).

However, given that uptake was so low, the researchers undertook a different analysis in which HBOT-adherent patients were instead compared to an estimated subgroup of the control arm that would likely have had the intervention if offered.

This analysis revealed that HBOT significantly decreased pain, with 32% of the intervention arm reporting moderate or severe pain at follow-up versus 75% among the control group expected to complete HBOT if offered (OR 0.3; p=0.01).

In the ITT population, there was a significant reduction in fibrosis, with moderate or severe fibrosis reported by 33% in the intervention arm and 51% in the control arm (OR, 0.36; p=0.02). However, HBOT did not significantly impact breast oedema, movement restriction or quality of life in either analysis.

The authors noted several important limitations of the study, including potential bias in response to the follow-up questionnaire (100% of the HBOT adherent group completed this compared to 85% of the control group),  the fact that the HBOT invitation group was younger and that HBOT-adherent patients were both younger and more often received follow-up care for late radiotherapy effects.

However, despite these caveats, “we now have modest evidence to justify the use of HBOT in treating the chronic morbidities associated with breast irradiation,” said a group of international editorialists (link here) including radiation oncologist Dr Ezra Hahn, Princess Margaret Cancer Centre, University of Toronto, Canada.

The intervention’s low uptake “also reminds us that convenience has become a factor weighted heavily by patients during the process of decision-making,” they added.

“Despite experiencing relatively severe symptoms, many declined hyperbaric therapy after being counselled by HONEY investigators about the time commitment imposed.

“This phenomenon is consistent with an analogous trend that has recently been observed among patients with breast cancer, who similarly prioritise convenience when selecting their initial treatments,” they said.

Looking forward, the editorialists said adequately powered randomised, sham-controlled, double-blind trials are necessary to truly determine the benefit of HBOT, though noted that this “will entail immense effort and considerable funding”.