Trends and Predictors of Total Neoadjuvant Therapy in Rectal Cancer: A Bi-National Registry Study Across Australia and New Zealand.

Abstract

Background: Total Neoadjuvant Therapy (TNT) has significantly improved outcomes in locally advanced rectal cancer. Despite rising use and inclusion in international guidelines, adoption patterns in Australia and New Zealand (ANZ) remain unclear. This study determines bi-national patterns and predictors of TNT utilisation over a 6-year period.

Methods: A retrospective population-based bi-national registry cohort study analysed data from the ANZ Bowel Cancer Outcome Registry from 2018 to 2024. Patients diagnosed with primary locally advanced rectal cancer (LARC) and treated with standard neoadjuvant therapy (SNT), consisting of long-course chemoradiotherapy or short-course radiotherapy, or TNT were included. The primary outcome was the incidence of TNT utilisation over time and determining pre-treatment predictive factors.

Results: Of 33 270 patient entries, 3234 eligible LARC patients were identified, with 706 (21.8%) receiving TNT and 2528 (78.2%) receiving SNT. TNT usage increased from 11% in 2018 to 41% in 2023. On multivariable logistic regression, independent factors associated with decreased TNT use were older age (OR: 0.978, 95% CI: 0.970-0.985, p < 0.001), absence of multidisciplinary team discussion (OR: 0.113, 95% CI: 0.027-0.472, p = 0.003) and private health insurance (OR: 0.619, 95% CI: 0.441-0.869, p = 0.006). Factors associated with increased TNT use were clinical T4 tumours (OR: 2.020, 95% CI: 1.245-3.280, p = 0.004), node-positive status (OR: 1.481, 95% CI: 1.118-1.964, p = 0.006) and diagnosis during the years 2019-2023 (p < 0.05 for all).

Conclusions: TNT is increasingly used in surgical rectal cancer patients captured in the BCOR in ANZ. This study provides a baseline for future benchmarking patterns of rectal cancer management.