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

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.

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.

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).

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.