HOPON (Hyperbaric Oxygen for the Prevention of Osteoradionecrosis): a randomised controlled trial of hyperbaric oxygen to prevent osteoradionecrosis of the irradiated mandible: study protocol for a randomised controlled trial

Background: Osteoradionecrosis of the mandible is the most common serious complication of radiotherapy for head and neck malignancy. For decades, hyperbaric oxygen has been employed in efforts to prevent those cases of osteoradionecrosis that are precipitated by dental extractions or implant placement. The evidence for using hyperbaric oxygen remains poor and current clinical practice varies greatly. We describe a protocol for a clinical trial to assess the benefit of hyperbaric oxygen in the prevention of osteoradionecrosis during surgery on the irradiated mandible. Methods/design: The HOPON trial is a phase III, randomised controlled, multi-centre trial. It employs an unblinded trial design, but the assessment of the primary endpoint, i.e. the diagnosis of osteoradionecrosis, is assessed on anonymised clinical photographs and radiographs by a blinded expert panel. Eligibility is through the need for a high-risk dental procedure in the mandible where at least 50-Gy radiotherapy has been received. Patients are randomised 1:1 to hyperbaric oxygen arm (Marx protocol) : control arm, but both groups receive antibiotics and chlorhexidine mouthwash. The primary endpoint is the presence of osteoradionecrosis at 6 months following surgery, but secondary endpoints include other time points, acute symptoms and pain, quality of life, and where implants are placed, their successful retention. Discussion: The protocol presented has evolved through feasibility stages and through analysis of interim data. The classification of osteoradionecrosis has undergone technical refinement to ensure that robust definitions are employed. The HOPON trial is the only multi-centre RCT conducted in this clinical setting despite decades of use of hyperbaric oxygen for the prevention of osteoradionecrosis. Trial registration: European Clinical Trials Database, ID: EudraCT200700622527. First registered on 5 November 2007

Taxonomy based on science is necessary for global conservation

Peer reviewe

Limited understanding of bushfire impacts on Australian invertebrates

1. Understanding how increasing risk of frequent and severe fires affects biodiversity and ecosystem function is important for effective conservation and recovery, but large knowledge gaps exist for many taxa in many parts of the world, especially invertebrates. 2. After Australia’s 2019–2020 catastrophic bushfire disaster, estimates of biodiversity loss and government priorities for post-fire conservation activities were focused on vertebrates and plants because of lack of knowledge about invertebrates. 3. Our synthesis of published evidence reveals a fragmented and ambiguous body of literature on invertebrate responses to fire in Australian ecosystems, limiting the capacity of evidence to inform effective conservation policy in response to extreme fire events. Peer-reviewed studies are available for only six of the more than 30 invertebrate phyla and 88% were on arthropods, predominantly ants. 4. Nearly all studies (94%) were conducted in terrestrial habitats, with only four studies measuring impacts in freshwater habitats and no studies of impacts on marine invertebrates. The high variation in study designs and treatment categories, as well as the absence of key methodological details in many older observational studies, means that there is substantial opportunity to improve our approach to collating meaningful estimates of general fire effects. 5. To understand the full ecological effects of catastrophic fire events, and design effective policies that support recovery of ecosystems now and in future, it is critical that we improve understanding of how fire regimes affect invertebrates. We list key priorities for research and policy to support invertebrate conservation and ecosystem recovery in the face of increasing fire risk