Prostate cancer outcomes disparities: Population survival analysis in an ethnically diverse nation

Prostate cancer represents a significant health burden on New Zealand men. There are increasing concerns regarding inequities in prostate cancer morbidity and mortality among the different ethnic groups in New Zealand. This study aims to assess ethnic differences in survival outcomes among men newly diagnosed with prostate cancer.

The analyzed cohort included 42,563 men, 40 years or older, diagnosed with prostate cancer from January 1st, 2000 to January 1st, 2016. Overall and cancer-specific survivals were estimated for the main ethnic groups in New Zealand namely: Māori (indigenous), Pacific, Asian, and European. Hazard ratio (HR) of death from prostate cancer was calculated with Fine-Gray competing risk regression, while adjusting for age, socioeconomic deprivation, year of cancer diagnosis, residential status, presence of urology service, and cancer grade at diagnosis.

Among all ethnic groups, Māori participants consistently had worst survival outcomes. At 15-year follow-up, the overall cumulative survival probabilities were 39.8%, 43.6%, 63.3%, and 46.5%, for Māori, Pacific, Asian and European men, respectively. In the same order, cancer-specific survivals were 62.7%, 64.3%, 79.8% and 72.0%. Māori men had 43% higher risk of dying from prostate cancer when compared to Europeans. This persisted following adjustments in the multivariable model (adjusted HR = 1.44, [95% CI: 1.29-1.61], P< 0.001). Conversely, differences in sociodemographic and cancer characteristics between Pacific and European men could explain the higher mortality risk in the former group (adjusted HR = 1.00, [95% CI: 0.84-1.19], P= 0.990).

Significant ethnic disparities in prostate cancer survival outcomes are currently present in New Zealand. Several explanations have been proposed to account for this observation including differences in comorbidities, healthcare access and cancer grade at diagnosis.