Poster Presentation Clinical Oncology Society of Australia Annual Scientific Meeting 2026

A moving feast: operationalising critical weight loss definitions in a real-world head and neck cancer cohort (146533)

Ghazaleh Niknam Shirvan 1 2 3 , Brianna Argall 2 , Tim Churches 1 2 , Nasreen Kaadan 1 4 , Gui Xiong 1 4 , Meera Agar 2 3 5 , Geoff Delaney 2 3 4 6 , Merran Findlay 1 2 3 4 7 8 , Georgina Kennedy 1 2 3 8
  1. Ingham Institute for Applied Medical Research, Liverpool, NEW SOUTH WALES, Australia
  2. South Western Sydney Clinical School, UNSW, Sydney, New South Wales, Australia
  3. Maridulu Budyari Gumal (SPHERE) Cancer Clinical Academic Group, UNSW, Sydney, NSW, Australia
  4. Liverpool & Macarthur Cancer Therapy Centres, South Western Sydney Local Health District, Sydney, NSW, Australia
  5. University of Technology Sydney, Sydney, NSW, Australia
  6. Ingham Institute for Applied Medical Research / UNSW, Sydney, NEW SOUTH WALES, Australia
  7. Chris O'Brien Lifehouse, Sydney, NSW, Australia
  8. corresponding author,

Background: "Critical weight loss" (CWL) is clinically important in cancer, yet thresholds are inconsistently defined and difficult to operationalise at scale. The common 5-10% cut-point is arbitrary [1], Body Mass Index (BMI)-adjusted "clinically important" thresholds range 5-20% across studies [2], and reported prevalence depends heavily on measurement window. Most adverse-event reporting and trials use %weight loss alone, without accounting for baseline BMI.

Methods: We modelled alternative weight-loss (WL) definitions using the Observational Medical Outcomes Partnership (OMOP) episode structure for comparison at scale across time windows. We computed %WL, timeframe-windowed %WL, and Martin et al.'s survival-validated, BMI-adjusted %WL grade across disease- and treatment-episode levels, in a head and neck cancer (HNC) cohort and a mixed-cancer comparison sample (real-world data from South Western Sydney). Descriptive statistics summarised WL distributions and grade prevalence and a chi-square test assessed height availability by treatment pattern.

Results: Apparent prevalence of ≥5% WL varied more than ten-fold according to measurement window (30-day: 5.5%; 90-day: 16.9%; 180-day: 33.3%; baseline-to-latest: 58.1%). HNC patients showed greater WL than the mixed-cancer sample (n=1,558 vs n=2,000; median %WL -7.4% vs -0.5%; 58.1% vs 25.4% meeting ≥ 5%). Among 1,148 episodes with both a %WL-only and BMI-adjusted grade computable, only 24% agreed: 76% shifted to a more severe grade once BMI was considered, and none improved. Height availability varied by treatment modality, from 89% (systemic therapy plus radiotherapy) to 68% (no treatment), consistent with height capture for body-surface-area systemic therapy dosing needs rather than nutritional surveillance (p<0.001).

Conclusion: Episode-level modelling demonstrated apparent CWL prevalence and severity vary substantially by measurement timeframe and whether BMI is incorporated. This framework offers a transparent and scalable approach to operationalising CWL definitions in routinely collected cancer data, while identifying data-quality issues relevant to future BMI-adjusted implementation.

 

  1. [1] Fearon, K., Strasser, F., Anker, S. D., Bosaeus, I., Bruera, E., Fainsinger, R. L., ... & Baracos, V. E. (2011). Definition and classification of cancer cachexia: an international consensus. The lancet oncology, 12(5), 489-495.
  2. [2] Martin, L., Senesse, P., Gioulbasanis, I., Antoun, S., Bozzetti, F., Deans, C., ... & Baracos, V. E. (2015). Diagnostic criteria for the classification of cancer-associated weight loss. Journal of clinical oncology, 33(1), 90-99.