Speaker's Highlight

• Don Sin University of British Columbia, St. Paul Hospital (Canada)
  Kenneth R. Chapman Toronto General Hospital Research Institute (Canada)
• Parameswaran Nair McMaster University (Canada)
  Carolyn Calfee UCSF (U.S.A.)
• Gregory P. Downey University of Colorado School of Medicine (U.S.A.)
  David A. Schwartz University of Colorado School of Medicine (U.S.A.)
• Neil Schluger Tuberculosis Control Branch, California Department of Public Health (U.S.A.)
  Nick Kim Critical Care & Sleep Medicine, University of California San Diego (U.S.A.)
• Nicola Hananiah Baylor College of Medicine (U.S.A.)
  Jae-Joon Yim Seoul National University College of Medicine (Republic of Korea)
• Koichiro Asano Tokai University School of Medicine (Japan)
  Diahn-Warng Perng Taipei Veterans General Hospital (Taiwan)
• Konstantinos Kostikas University of Ioannina (Greece)
  Karin Klooster University Medical Center Groningen (Kingdom of the Netherlands)

• Exhaled Breath Condensate and Lung Cancer Biomarker Discovery

  Lung cancer remains the leading cause of cancer-related death in Australia, with the Australian Institute of Health and Welfare reporting roughly 13,000 new cases each year. Survival sits at around 22% at five years, a figure that has barely shifted in two decades. Most diagnoses still occur once disease has already spread, when treatment options narrow considerably. That stubborn gap between incidence and outcomes has pushed researchers in Sydney, Melbourne and Perth to explore screening tools that are both more sensitive and easier to deploy than the low-dose CT scans that dominate current protocols.

  Exhaled breath condensate is one such tool, offering a window into the lower airways through a sample that patients can provide in minutes. The fluid, gathered by breathing into a cooled chamber, carries traces of volatile organic compounds, proteins, DNA fragments and inflammatory mediators. Researchers are now cataloguing which of these molecules shift in meaningful ways when malignancy is present, hoping to build a panel that flags disease before nodules are visible on a scan.

  The appeal is partly practical and partly biological. A breath test fits comfortably into a GP consult in suburban Parramatta or a regional clinic in Townsville, requires no fasting, no radiation, and no specialist equipment beyond a portable condenser. It also reaches populations who are reluctant to undergo invasive procedures, including some Aboriginal and Torres Strait Islander communities where engagement with hospital-based screening has historically been low. That combination of accessibility and molecular depth is what makes the field worth watching.

  The biology of breath condensate

  Breath condensate forms when water vapour in exhaled air meets a cold surface, typically chilled to around zero degrees. The resulting liquid captures both water-soluble and aerosolised compounds from the lining fluid of the airways. Among the most studied constituents are hydrogen peroxide, nitrite, cytokines, leukotrienes and short-chain fatty acids. Many of these are present in healthy lungs at trace levels, so the analytical challenge lies in detecting subtle shifts rather than absolute presence.

  In patients with lung cancer, several of these molecules behave differently. Levels of certain aldehydes rise, pH trends acidic, and tumour-derived DNA can sometimes be recovered. The patterns are not unique to malignancy, however. Chronic obstructive pulmonary disease, asthma and acute infections can produce overlapping signatures, which is why any single biomarker is unlikely to be diagnostic on its own.

  Biomarkers currently under investigation

  The candidate list is growing fast. Endogenous volatile organic compounds such as hexanal, heptanal and decane have shown promise in pilot cohorts run through Australian research hospitals. MicroRNAs, particularly the miR-21 and miR-155 family, are detectable in condensate and correlate with tumour histology in some small studies. Exhaled DNA fragmentation patterns, including methylation signatures, are also under examination, with teams at the Peter MacCallum Cancer Centre in Melbourne publishing early data on feasibility.

  A practical issue is that concentrations sit at the edge of what current assays can reliably measure. A typical condensate sample yields 1–2 millilitres of liquid, with target molecules often present in picomolar quantities. Mass spectrometry and digital PCR have improved sensitivity, but standardisation between labs remains incomplete. For clinicians, that means published results should be read alongside the methodology rather than as universal cut-offs.

  Comparison with sputum cytology and imaging

  Traditional sputum cytology has been available for decades yet never gained traction in Australia outside research settings because of its modest sensitivity, particularly for peripheral tumours. Low-dose CT, by contrast, is the gold standard in major screening trials, with the National Lung Cancer Screening Program now in early rollout phases. Imaging captures structural change; breath condensate captures biochemical change, and the two approaches answer different questions.

  Blood-based liquid biopsies, including circulating tumour DNA and cancer antigen panels, have moved faster into clinical use. They share the non-invasive appeal of breath testing but require phlebotomy and laboratory turnaround times of several days. EBC results, in principle, can be available within hours once the workflow is mature. Cost per test is also likely to compare favourably with imaging, which depends on a CT scanner and radiologist review.

  Clinical workflow and patient experience

  The mechanics of collection are deliberately simple. A patient breathes tidally through a mouthpiece connected to a condenser for ten to fifteen minutes. The device is portable, weighing a few kilograms, and runs on mains or battery power. There is no need to stop medications, no fasting, and no recovery time, which makes it suitable for mobile health units visiting places like Broken Hill or remote Western Australian communities.

  The downstream workflow is more involved. Samples must be frozen promptly, transported on dry ice, and stored at minus eighty degrees to prevent degradation. Analysis requires either a mass spectrometer or a PCR-based platform, both of which sit in tertiary centres. That bottleneck has so far kept exhaled breath condensate firmly in the research domain rather than routine general practice. The roadmap to clinical use runs through pathology providers, not respiratory clinics, at least initially.

  Australian research efforts

  Several groups are pushing the field forward. The Woolcock Institute in Sydney has run pilot studies on volatile organic compound profiling in people with suspicious nodules identified through their screening work. The Harry Perkins Institute in Perth is collaborating with respiratory physicians on microRNA panels, and the latest updates from the APSR research network detail collaborative efforts across the Asia-Pacific region, including Australian sites.

  Funding has come through the National Health and Medical Research Council and Cancer Australia, with industry partnerships supplementing government support. Ethical frameworks developed here, particularly around Indigenous data governance, are being adapted for biomarker studies involving Aboriginal participants. The Australian approach favours cautious, multi-site validation over single-centre claims, which has slowed hype but improved reproducibility.

  Technical challenges and reproducibility

  Variability is the field's biggest headache. The volume of condensate collected depends on minute ventilation, ambient humidity, device temperature and how deeply a patient breathes. One study can record a sample as 0.5 mL while another, using a different protocol, records 2.5 mL from a similar patient. Without normalisation, biomarker concentrations become hard to compare across studies.

  Standardisation efforts are underway through bodies such as the European Respiratory Society, whose task force on EBC has published guidance that Australian labs generally follow. Internal standards, like dilution with conductive measurements, are helping. So are automated sampling devices that control breathing pattern. None of this is glamorous work, but it is the foundation on which any future screening claim will rest.

  Comparing diagnostic approaches for early lung cancer detection

  Method	Sample type	Invasiveness	Turnaround	Sensitivity for early disease	Suitability for regional Australia
  Exhaled breath condensate	Breath fluid	Very low	Hours (potential)	Under investigation, variable	High if logistics solved
  Sputum cytology	Sputum	Low	1–2 days	Low, especially peripheral tumours	Moderate
  Low-dose CT	Imaging	None (radiation exposure)	Same day to 1 week	High for solid nodules	Limited by scanner access
  Blood liquid biopsy	Venous blood	Low–moderate	3–7 days	Improving, varies by stage	Moderate, requires pathology hub
  Bronchoscopy	Tissue	High	3–5 days	High when lesion accessible	Limited to tertiary centres

  The picture that emerges is one of complementary tools rather than a single winner. Imaging will remain the structural backbone, blood tests the molecular backbone, and breath condensate, if validated, the accessible front door. For clinicians working outside major cities, that front door matters more than any other consideration.

  A practical takeaway for Australian clinicians is to view exhaled breath condensate as an emerging adjunct rather than a replacement for established pathways. Patients with indeterminate pulmonary nodules, those at high risk who decline CT, and individuals in remote communities are realistic first candidates. Engagement with pathology providers now, while commercial assays are still being refined, will put practices in a strong position when a clinically validated panel becomes available. The technology is not yet ready for the MBS schedule, but it is ready for collaborative research, and that is where the next few years of progress will be made.

  Richard Russell Nuffield Department of Clinical Medicine, University of Oxford (United Kingdom)
• Mona Bafadhel King’s College London (United Kingdom)
  David Jackson Guy’s and St Thomas’ Hospital, King’s College London (United Kingdom)
• James Chalmers University of Dundee (United Kingdom)
  David Price University of Aberdeen (United Kingdom)