Background
In 2009, Ireland’s National Cancer Control Programme introduced Rapid Access Prostate Clinics (RAPCs) within designated cancer centres to streamline assessment for suspected prostate cancer in men aged 50-70. Despite wide uptake, their population?level impact has not been evaluated using robust quasi?experimental methods.

Objectives
To estimate the association between RAPC implementation and changes in (i) overall prostate cancer diagnosis rates, (ii) stage at diagnosis, and (iii) hospital setting of diagnosis among men aged 50–70 years.

Methods
We included all patients diagnosed with prostate cancer between 2000 and 2019 and registered in the National Cancer Registry Ireland (n=60358). We constructed quarterly time series and conducted an interrupted time series analysis using negative binomial regression. We used the male 50–70 population as offset with  case counts and crude incidence as outcomes. We estimated counts for the entire cohort, stage?specific (I–IV) and by hospital type (cancer centres, public non?cancer centres, private). We estimated immediate level change and slope change between pre?implementation (2000–2008) and implementation (2009–2019) periods.

Results
Mean quarterly diagnoses increased from 321 pre?implementation to 570 following RAPC introduction. Crude quarterly incidence rose from 325.0 to 458.4 per 100,000 person?years. We observed an immediate increase of approximately 18 additional cases at implementation, with the slope shifting from an increase of 5.4 cases per quarter before RAPCs to a decrease of less than 1 per quarter after, indicating that growth slowed but incidence remained higher than pre?implementation levels. Stage I showed the largest absolute rise (mean 120 to 263 per quarter). Stage II diagnoses declined significantly post?implementation, reversing from a steady increase to a downward trend with a decrease of 3.5 cases per quarter (95% CI: –4.3 to –2.7). No reduction was observed for Stage III, while Stage IV diagnoses increased significantly with an increase of 0.5 cases per quarter (95% CI: 0.2 to 0.7). Diagnostic activity shifted markedly from public hospitals to cancer centres (mean 93 to 275 per quarter), with private hospitals also increasing; public hospital diagnoses fell (137 to 110 per quarter). The slope change was most pronounced in public hospitals, where the pre?implementation upward trend reversed to a significant decline after RAPC introduction (–3.4 cases per quarter, 95% CI: –4.2 to –2.7).

Conclusions/Implications
RAPCs successfully centralised prostate cancer diagnostics within cancer centres and improved early-stage detection. However, the persistence of late-stage disease and a rise in Stage IV cases indicate that RAPCs alone have not eliminated advanced presentations. Diagnostic activity shifted from public hospitals to cancer centres, consistent with the intended reorganisation of care. These findings highlight the need for continued investment in specialist-led pathways, optimisation of referral criteria, and capacity planning to ensure timely diagnosis across all stages.