Risk of prostate cancer death in men diagnosed with prostate cancer at cystoprostat-ectomy. A nationwide population-based study.

Background and aims: One out of three men who undergo cystoprostatectomy for bladder cancer is diagnosed with incidental prostate cancer (PCa) at histopathological examination. Many of these men are PSA tested as part of their follow-up, but it is unclear if this is needed. The aim of this study was to assess the risk of PCa death in these men and the need of PSA-testing during follow-up.

Methods: Between 2002 and 2020, 1,554 men were diagnosed with PCa after cystoprostatectomy performed for non-metastatic bladder cancer and registered in the National Prostate Cancer Register (NPCR) of Sweden. We assessed their risk of death from PCa, bladder cancer and other causes up to 15 years after diagnosis by use of data in The Cause of Death Register. The use of androgen deprivation therapy (ADT) as a proxy for PCa progression was assessed by fillings in The Prescribed Drug Register.

Results: Fifteen years after diagnosis, cumulative incidence of death from PCa was 2.6% (95% CI 2.3%-2.9%), from bladder cancer 32% (95% CI: 30%-34%) and from other causes 40% (95% CI: 36%-44%). Only 35% of men with PCa recorded as primary cause of death in The Cause of Death Register had started ADT before date of death, indicating sticky-diagnosis bias with inflated risk of PCa death.

Conclusions: For a large majority of men diagnosed with incidental PCa at cystoprostatectomy performed for bladder cancer, the risk of PCa death is very small so there is no rationale for PSA testing during follow-up.