Outcomes and progression predictors in a New Zealand active surveillance programme for prostate cancer

OBJECTIVE: To describe outcomes and identify predictors of histological progression in men on active surveillance (AS) for International Society of Urological Pathology Grade Group (ISUP GG) 1 prostate cancer in New Zealand (NZ), as AS is the standard management for favourable-risk prostate cancer, yet NZ-specific outcome data remain limited. PATIENTS AND METHODS: A retrospective study of the North Shore Hospital AS programme (2014-2020) was conducted. Records were reviewed in 2024. In total, 296 men with ISUP GG 1 disease on AS were included. Primary endpoints were histological progression to ISUP GG ≥2, treatment conversion, and disease-related mortality. RESULTS: Over a mean 7.4-year follow-up, 36.5% progressed, 33.4% required treatment, 12.1% recurred after treatment, and one patient died from metastatic disease. Within the cohort, a low-risk subgroup of 93 patients with ISUP GG 1 prostate cancer had low prostate-specific antigen (PSA) density and no suspicious magnetic resonance imaging (MRI) lesions. Of these patients, 16 (17.2%) progressed. On multivariate analysis, independent predictors of progression were PSA density ≥0.15 ng/mL/mL (odds ratio [OR] 3.45) and Prostate Imaging-Reporting and Data System 3-5 lesions (OR 3.52). CONCLUSION: Active surveillance is a safe option for low-risk prostate cancer, our data are consistent with outcomes consistent with the Prostate Cancer Outcomes Registry and international data. PSA density and multiparametric MRI were the strongest predictors of progression; tumour volume by percentage of positive cores was not independently predictive. New draft Prostate Cancer Foundation of Australia guidelines recommend against biopsy in men with PSA density <0.15 ng/mL/cc and no PIRADS 3-5 lesion on MRI[7], in our cohort this included many men with ISUP 1 cancer. They had a 17.2% progression rate to ISUP ≥2, and their clinically significant disease might have been missed without close surveillance.