RESUMEN
Importance: Prostate cancer screening remains controversial because potential mortality or quality-of-life benefits may be outweighed by harms from overdetection and overtreatment. Objective: To evaluate the effect of a single prostate-specific antigen (PSA) screening intervention and standardized diagnostic pathway on prostate cancer-specific mortality. Design, Setting, and Participants: The Cluster Randomized Trial of PSA Testing for Prostate Cancer (CAP) included 419â¯582 men aged 50 to 69 years and was conducted at 573 primary care practices across the United Kingdom. Randomization and recruitment of the practices occurred between 2001 and 2009; patient follow-up ended on March 31, 2016. Intervention: An invitation to attend a PSA testing clinic and receive a single PSA test vs standard (unscreened) practice. Main Outcomes and Measures: Primary outcome: prostate cancer-specific mortality at a median follow-up of 10 years. Prespecified secondary outcomes: diagnostic cancer stage and Gleason grade (range, 2-10; higher scores indicate a poorer prognosis) of prostate cancers identified, all-cause mortality, and an instrumental variable analysis estimating the causal effect of attending the PSA screening clinic. Results: Among 415â¯357 randomized men (mean [SD] age, 59.0 [5.6] years), 189â¯386 in the intervention group and 219â¯439 in the control group were included in the analysis (n = 408â¯825; 98%). In the intervention group, 75â¯707 (40%) attended the PSA testing clinic and 67â¯313 (36%) underwent PSA testing. Of 64â¯436 with a valid PSA test result, 6857 (11%) had a PSA level between 3 ng/mL and 19.9 ng/mL, of whom 5850 (85%) had a prostate biopsy. After a median follow-up of 10 years, 549 (0.30 per 1000 person-years) died of prostate cancer in the intervention group vs 647 (0.31 per 1000 person-years) in the control group (rate difference, -0.013 per 1000 person-years [95% CI, -0.047 to 0.022]; rate ratio [RR], 0.96 [95% CI, 0.85 to 1.08]; P = .50). The number diagnosed with prostate cancer was higher in the intervention group (n = 8054; 4.3%) than in the control group (n = 7853; 3.6%) (RR, 1.19 [95% CI, 1.14 to 1.25]; P < .001). More prostate cancer tumors with a Gleason grade of 6 or lower were identified in the intervention group (n = 3263/189â¯386 [1.7%]) than in the control group (n = 2440/219â¯439 [1.1%]) (difference per 1000 men, 6.11 [95% CI, 5.38 to 6.84]; P < .001). In the analysis of all-cause mortality, there were 25â¯459 deaths in the intervention group vs 28â¯306 deaths in the control group (RR, 0.99 [95% CI, 0.94 to 1.03]; P = .49). In the instrumental variable analysis for prostate cancer mortality, the adherence-adjusted causal RR was 0.93 (95% CI, 0.67 to 1.29; P = .66). Conclusions and Relevance: Among practices randomized to a single PSA screening intervention vs standard practice without screening, there was no significant difference in prostate cancer mortality after a median follow-up of 10 years but the detection of low-risk prostate cancer cases increased. Although longer-term follow-up is under way, the findings do not support single PSA testing for population-based screening. Trial Registration: ISRCTN Identifier: ISRCTN92187251.
Asunto(s)
Detección Precoz del Cáncer , Tamizaje Masivo , Antígeno Prostático Específico/sangre , Neoplasias de la Próstata/diagnóstico , Distribución por Edad , Anciano , Estudios de Seguimiento , Humanos , Masculino , Persona de Mediana Edad , Atención Primaria de Salud , Neoplasias de la Próstata/sangre , Neoplasias de la Próstata/mortalidad , Clase Social , Reino Unido/epidemiologíaRESUMEN
OBJECTIVES: Randomized controlled trials (RCTs) deliver robust internally valid evidence but generalizability is often neglected. Design features built into the Prostate testing for cancer and Treatment (ProtecT) RCT of treatments for localized prostate cancer (PCa) provided insights into its generalizability. STUDY DESIGN AND SETTING: Population-based cluster randomization created a prospective study of prostate-specific antigen (PSA) testing and a comprehensive-cohort study including groups choosing treatment or excluded from the RCT, as well as those randomized. Baseline information assessed selection and response during RCT conduct. RESULTS: The prospective study (82,430 PSA-tested men) represented healthy men likely to respond to a screening invitation. The extended comprehensive cohort comprised 1,643 randomized, 997 choosing treatment, and 557 excluded with advanced cancer/comorbidities. Men choosing treatment were very similar to randomized men except for having more professional/managerial occupations. Excluded men were similar to the randomized socio-demographically but different clinically, representing less healthy men with more advanced PCa. CONCLUSION: The design features of the ProtecT RCT provided data to assess the representativeness of the prospective cohort and generalizability of the findings of the RCT. Greater attention to collecting data at the design stage of pragmatic trials would better support later judgments by clinicians/policy-makers about the generalizability of RCT findings in clinical practice.